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SSPC Protective Coatings Inspector (PCI) Program
July 2015
40 24th Street, Sixth Floor Pittsburgh, PA 15222 - 4656 Phone: 412-281-2331 Fax: 412-281-9993 Online: www.sspc.org Copyright 2015 SSPC: The Society for Protective Coatings
Version 1, May 2005 SSPC Protective Coatings Inspector (PCI) Program
July 2015
40 24th Street, Sixth Floor Pittsburgh, PA 15222 - 4656 Phone: 412-281-2331 Fax: 412-281-9993 Online: www.sspc.org Copyright 2015 SSPC: The Society for Protective Coatings
SSPC: The Society for Protective Coatings
is an international association focused on the protection and preservation of steel, concrete, and other industrial and marine structures and surfaces through the use of protective coatings. SSPC is the leading source of information on surface preparation, coating selection, coating application, environmental regulations, and health and safety issues — as they relate to the industrial protective coatings industry. The association’s many services include standards, training courses, certification programs, publications, conferences, and a variety of online resources. SSPC currently has over 900 company members and more than 10,500 individual members worldwide.
SSPC offers you: Abrasive Blasting Program (C7) Aerospace Coating Application Specialist Certification Program (ACAS) Applicator Train-the-Trainer Program Applicator Training Basics (ATB) eCourse Applicator Training Specialty Module CDs Basics of Concrete Surface Preparation eCourse Basics of Estimating Industrial Coatings Projects Basics of Nonferrous eCourse Basics of Steel Surface Preparation eCourse Bridge Coatings Inspector Program (BCI) Bridge Maintenance: Conducting Coating Assessments Coating Application Specialist Certification Program (CAS) Concrete Coating Basics Concrete Coating Inspector Program (CCI) CCI Supplement: Determining the Level of Moisture in Concrete Developing an Effective Coating Specification Evaluating Common Coating Contract Clauses Floor Coating Basics Fundamentals of Protective Coatings (C1) Fundamentals of Protective Coatings (C1) eCourse Inspecting Containment Inspection Planning and Documentation Lead Paint Removal (C3) Lead Paint Removal Refresher (C5) Lead Paint Worker Safety Marine Coatings Marine Coatings eCourse Marine Plural Component Program (MPCAC, C14) Master Coatings Inspector Certificate (MCI) Natural and Accelerated Weathering of Coatings
Navigating Standard Item 009-32 NAVSEA Basic Paint Inspector (NBPI) Planning and Specifying Industrial Coatings Projects (C2) Planning and Specifying Industrial Coatings Projects (C2) eCourse Plural Component Application for Polyureas and High-Solids Coatings Project Management for the Industrial Painting Contractor Protective Coatings Inspector Program (PCI) Protective Coating Inspector--One-Day Workshop Protective Coatings Inspector Program (PCI) Online Protective Coatings Specialist (PCS) Program Quality Control Supervisor (QCS) Quality Control Supervisor (QCS) eCourse Selecting Coatings Spray Applicator Certification (C12) Thermal Spray Training Using SSPC PA 2 Effectively Webinars Waterjetting Program (C13) Standards and Publications Annual Conference Online Services www.sspc.org
Monthly Journal
Journal of Protective Coatings and Linings For more information call SSPC toll-free in the U.S. at 877-281-7772; outside of the U.S. at 412281-2331; or visit us online at www.sspc.org. SSPC training programs are copyrighted world-wide by SSPC: The Society for Protective Coatings. Any photocopying, re-selling, or redistribution of this training program by printed, electronic, or any other means is strictly prohibited without the express written consent of SSPC: The Society of Protective Coatings and a formal licensing agreement.
Disclaimer The techniques, procedures, referenced regulations and standards, and other information presented in this SSPC training program have been reviewed by technical experts and every reasonable effort has been made to present accurate and up-to-date information at the time of publication. While every precaution has been taken to ensure that all of the information contained herein is as accurate and complete as feasible, it must be understood that regulations, standards and practices do change periodically in between publication dates of SSPC training materials. Every SSPC training program is reviewed and revised regularly to reflect these changes; however, SSPC cannot assume responsibility or obligation for any use or misuse of this information or misinterpretation of the standards and practices discussed. The student is advised to always consult the latest version of a regulation or standard for a review of current practice and correct procedures. Students are also welcome to contact SSPC to suggest revisions for future editions of the training materials contained herein.
Table of Contents Introduction Welcome and Course Introduction...................................................................................................... I-1 Participation Guidelines...................................................................................................................... I-2 The Course Syllabus........................................................................................................................... I-2 An Introduction to SSPC’s Protective Coatings Inspector Training .................................................. I-3 Module One: Protecting Metal Surfaces From Corrosion: The Role of High Performance Coatings.......................................................................................................... I-3 Module Two: The Roles of Quality Assurance (QA) and Quality Control (QC) Inspectors on a Coatings Project.................................................................................................. I-4 Module Three: Surface Preparation.................................................................................................... I-4 Module Four: Practical Arithmetic for the Coatings Inspector........................................................... I-6 Module Five: Coating Mixing, Thinning, and Application................................................................ I-6 Module Six: Industrial Protective Coatings and Coating Systems..................................................... I-8 Module Seven: Specialty Inspection Projects..................................................................................... I-8 Module Eight: Coating Failures and Methods of Prevention............................................................. I-9 Module Nine: Inspector Safety........................................................................................................... I-9 Module Ten: Coatings Specifications................................................................................................. I-9 Module Eleven: Pre-construction Conference and Inspection Procedure Development.................. I-10 Module Twelve: Project Inspection Workshop................................................................................. I-10 Module Thirteen: International Maritime Organization (IMO)........................................................ I-11 SSPC Protective Coatings Inspector Training and Certification Program........................................ I-11 Use of Materials and Textbooks........................................................................................................ I-13 An Orientation to the Coatings Industry and Key Organizations..................................................... I-13 Learning Outcomes........................................................................................................................... I-14
Module 1: Protecting Metal Surfaces From Corrosion: The Role of High Performance Coatings Corrosion Defined...............................................................................................................................1-1 The Role of Protective Coatings in Preventing/Slowing Corrosion...................................................1-2
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The Fundamentals of Corrosion..........................................................................................................1-2 Energy Required to Convert Ores into Metals....................................................................................1-4 Dissimilar Metals................................................................................................................................1-5 Corrosion Versus Oxidation................................................................................................................1-6 What is Steel?.....................................................................................................................................1-6 Weathering Steel.................................................................................................................................1-7 How Coatings Protect the Substrate from Corrosion..........................................................................1-7 Additional Cathodic Protection...........................................................................................................1-8 Summary...........................................................................................................................................1-12
Module 2a: The Roles of QA and QC Inspection Personnel on a Coatings Project Quality Assurance vs. Quality Control.............................................................................................2a-1 Pre-construction (Pre-job) Conference.............................................................................................2a-7 Development of an Inspection Procedure (Plan)..............................................................................2a-9
Module 2b: Ethics (U.S. only) Ethics.................................................................................................................................................2b-1
Module 3: Surface Preparation: Methods, Industry Standards and Inspection Introduction.........................................................................................................................................3-1 Module 3 Learning Outcomes............................................................................................................3-2 Overview.............................................................................................................................................3-2 The Inspector’s Role...........................................................................................................................3-3 Purpose of Surface Preparation...........................................................................................................3-3 Inspection of Surface Preparation.......................................................................................................3-3 Review of Industry Standards.............................................................................................................3-4 Pre-surface Preparation Inspection.....................................................................................................3-7 Preparation of Welds in Tanks and Vessels for Immersion Service....................................................3-8 Testing for Chemical Contamination................................................................................................3-16 How Do I Test for Soluble Salt Contamination?..............................................................................3-17 How Do I Test for Specific Ions and Conductivity?.........................................................................3-17 Selecting a Field Sampling and Testing Method..............................................................................3-18 Protective Coatings Inspector Training ©2013 SSPC
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Methods of Sample Collection Surface Sampling Method A: Surface Swabbing (Swab SCAT Kit)................................................3-20 Surface Sampling Method B: Latex Sleeve (Chlor*TestTM SCAT Kit)............................................3-20 Surface Sampling Method C: Latex Cell (Bresle PatchTM and BresleSampler®)............................3-20 Methods of Sample Testing Converting Between Surface Conductivity and Surface Concentration...........................................3-21 Analyzing Surface Extactions for the Sulfate Ion.............................................................................3-24 Measuring Ambient Conditions........................................................................................................3-23 Using Electronic Psychrometers to Measure Ambient Conditions...................................................3-24 Using Surface Temperature Measuring Instruments.........................................................................3-26 Calibrating Instruments for Measuring Ambient Conditions and Surface Temperature..................3-27 Documenting Ambient Conditions and Surface Temperature..........................................................3-27 Dehumidification...............................................................................................................................3-28 Assessing Lighting and Surface Cleanliness....................................................................................3-31 Methods of Surface Preparation........................................................................................................3-33 Selecting a Visual Standard..............................................................................................................3-39 Using SSPC-VIS 3, “Guide and Reference Photographs for Steel Surfaces Prepared by Power and Hand Tool Cleaning”................................................................................................3-41 Using SSPC-VIS 1, “Guide and Reference Photographs for Steel Surfaces Prepared by Dry Abrasive Blast Cleaning”....................................................................................................3-59 Using SSPC-VIS 5/NACE VIS 9, “Guide and Reference Photographs for Steel Surfaces Prepared by Wet Abrasive Blast Cleaning”................................................................................3-68 Conducting a Compressed Air Cleanliness (Blotter) Test................................................................3-76 Abrasives...........................................................................................................................................3-78 Abrasive Cleanliness.........................................................................................................................3-82 Measuring Surface Profile Depth......................................................................................................3-83 Using the Surface Profile Comparator..............................................................................................3-85 Using the Surface Profile Depth Gage..............................................................................................3-85 Using Replica Tape .........................................................................................................................3-85 Calibrating Surface Profile Measuring Instruments..........................................................................3-86 Documenting Surface Profile Measurements ...................................................................................3-87 Using Portable Stylus Instruments for Determining Peak Density...................................................3-87 Waterjetting.......................................................................................................................................3-89 SSPC/NACE Joint Surface Preparation Standards Waterjetting of Metals......................................3-90
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Using SSPC-VIS 4 /NACE VIS 7, “Guide and Reference Photographs for Steel Surfaces Prepared by Waterjetting”...........................................................................................................3-92 Chemical Stripping...........................................................................................................................3-99 Inspection of Surfaces for Primer Application................................................................................3-100 Summary.........................................................................................................................................3-102 Instrument Use Supplement...............................................................................................3-137 Using Psychrometers to Measure Ambient Conditions......................................................................1-2 Using Electronic Psychrometers to Assess Ambient Conditions and Surface Temperature...............1-8 Using Surface Temperature Measuring Instruments.........................................................................1-17 Calibrating Instruments for Measuring Ambient Conditions and Surface Temperature..................1-19 Documenting Ambient Conditions and Surface Temperature..........................................................1-20 Using the Keane-Tator Surface Profile Comparator...........................................................................2-2 Using Digital Surface Profile Gages...................................................................................................2-5 Using Replica Tape...........................................................................................................................2-10 Calibrating Surface Profile Measuring Instruments..........................................................................2-14 Documenting Surface Profile Measurements....................................................................................2-15 How to Test for Soluble Salt Contamination......................................................................................4-2 How to Test for Specific Ions and Conductivity.................................................................................4-3 Selecting a Field Sampling and Testing Method................................................................................4-4 Collecting a Sample............................................................................................................................4-6 Surface Sampling Method B.............................................................................................................4-10 Surface Samping Method C..............................................................................................................4-12 Testing the Collected Samples..........................................................................................................4-18 Sample Testing Method 5: Conductivity..........................................................................................4-31 Combination Extraction and Analysis..............................................................................................4-35
Module 4: Practical Arithmetic for the Protective Coatings Inspector Learning Outcome..............................................................................................................................4-1 Introduction.........................................................................................................................................4-2 Averaging a Set of Values...................................................................................................................4-2 Converting Percentages to Decimal Format.......................................................................................4-4 Calculating Area..................................................................................................................................4-5 Converting Volatile Organic Compound (VOC) Content Values.....................................................4-17 Converting Temperature...................................................................................................................4-18 Converting Units Used to Express Coating Thickness and Surface Profile Depth...........................4-19 Protective Coatings Inspector Training ©2013 SSPC
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Calculating Wet Film Thickness.......................................................................................................4-20 Calculating the Target Wet Film Thickness......................................................................................4-20 Calculating Coating Coverage Rates and Estimating Material Quantities.......................................4-26 Summary...........................................................................................................................................4-31
Module 5: Coating Mixing, Thinning and Application: Equipment Overview and Inspection Techniques Introduction.........................................................................................................................................5-1 Learning Outcomes.............................................................................................................................5-2 The Inspector’s Role...........................................................................................................................5-2 Review of SSPC Standards for Coating Application..........................................................................5-3 Coating Manufacturer’s Technical Data Bulletins/Product Data Sheets............................................5-4 Material Receipt Inspection and Storage Conditions........................................................................5-14 Inspection of Mixing, Thinning and Application of Coatings..........................................................5-16 Measuring Coating Temperature.......................................................................................................5-19 Documentation and Reporting Procedures Relating to Inspection of Coating Mixing....................5-20 Coating Mixing Procedures..............................................................................................................5-20 Coating Thinning Procedures...........................................................................................................5-24 Inspecting Thinning Procedures.......................................................................................................5-27 Documentation and Reporting Procedures Relating to Inspection of Thinning (reducing).............5-28 Coating Application Methods...........................................................................................................5-28 Spray Technique................................................................................................................................5-35 Calculating Wet Film Thickness.......................................................................................................5-37 Calculating the Target Wet Film Thickness......................................................................................5-38 Measuring Wet Film Thickness........................................................................................................5-43 Measuring Dry Film Thickness........................................................................................................5-44 Measuring the Thickness of Individual Layers Using Destructive Means.......................................5-51 Documentation Procedures Relating to Inspection of Dry Film Thickness.....................................5-53 Assessing Intercoat Cleanliness........................................................................................................5-54 Detecting Amine Exudate (Blush) on Polyamide and Polyamide-Cured Surfaces..........................5-54 Documentation Procedures Relating to Verification of Intercoat Cleanliness and Conformance to Recoat Intervals...............................................................................................5-55 Assessing Coating Cure....................................................................................................................5-55 Assessing Coating Film Hardness....................................................................................................5-57 Measuring Adhesion.........................................................................................................................5-60 Detecting Pinholes and Holidays .....................................................................................................5-63 Protective Coatings Inspector Training ©2013 SSPC
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Verifying the Accuracy of High Voltage Holiday Detectors.............................................................5-65 Inspecting Fluorescent Coating Systems..........................................................................................5-66 Summary...........................................................................................................................................5-68
Instrument Use Supplement...............................................................................................5-101 Calculating Target Wet Film Thickness..............................................................................................5-2 Measuring Wet Film Thickness..........................................................................................................5-5 Adjusting and Using the Elcometer®456 wht PINIP™ Probe.........................................................6-23 Adjusting and Using the Fischer Dualscope® MPOR.....................................................................6-27 What is a Tooke Gage?.......................................................................................................................8-1 Measuring Adhesion by the Knife Test (ASTM D6677)..................................................................9-11 Measuring Pull-Off Adhesion (ASTM D4541; ASTM D7234).......................................................9-13 Measuring Adhesion Using the Elcometer® Model 106..................................................................9-15 Measuring Adhesion Using the HATE® Adhesion Tester................................................................9-22 Measuring Adhesion Using the PATTI® Quantum Series Analog Adhesion Tester........................9-28 Measuring Adhesion Using the PosiTest® AT Adhesion Tester.......................................................9-38 Special Requirements for Tensile Adhesion Testing of Coatings on Concrete.................................9-45 Tensile Adhesion Testing: Record the Type and Location of Break.................................................9-47 What are Pinholes and Holidays?.....................................................................................................10-1 Selecting a Holiday Detector............................................................................................................10-2 Using a Low-Voltage (Wet Sponge) Holiday Detector.....................................................................10-3 Using a High-Voltage (Spark) Holiday Detector..............................................................................10-6 Verifying the Accuracy of High-Voltage Holiday Detectors..........................................................10-11
Module 6: Industrial and Marine Protective Coatings and Coating Systems Introduction.........................................................................................................................................6-1 Industrial and Marine Protective Coatings Versus Paint.....................................................................6-3 Industrial/Marine Coatings: Components...........................................................................................6-3 Curing Mechanisms............................................................................................................................6-8 Identifying the Service Environment................................................................................................6-10 Characteristics by Coating/Lining Type...........................................................................................6-11 Key Inspection Concerns by Coating/Lining Type...........................................................................6-14 Coating Systems Defined..................................................................................................................6-16 Coating System Selection.................................................................................................................6-17 Protective Coatings Inspector Training ©2013 SSPC
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Performance Evaluation of Protective Coating Systems..................................................................6-28 Summary...........................................................................................................................................6-30
Module 7: Specialty Inspection Projects Introduction.........................................................................................................................................7-1 Coatings Inspection in the Steel Fabrication Shop.............................................................................7-3 Inspection of Thermal (Metallized) Spray Coatings (TSC)................................................................7-6 Measuring the Thickness of Thermal Spray Coatings........................................................................7-8 Inspection of Powder Coatings...........................................................................................................7-9 Inspection of Galvanized Systems....................................................................................................7-11 Inspecting Overcoating Projects ......................................................................................................7-13 Inspecting on Projects Involving Removal of Toxic Metal Coatings...............................................7-18 Summary...........................................................................................................................................7-25
Module 8: Coating Failures: Consequences and Case Studies Introduction.........................................................................................................................................8-1 The Role of the Coatings Inspector in Failure Avoidance..................................................................8-3 The Role of the Coatings Inspector in a Failure Investigation...........................................................8-3 Case Studies of Coating Failure..........................................................................................................8-4 Summary...........................................................................................................................................8-17
Module 9: Coatings Inspector Safety Introduction.........................................................................................................................................9-1 General Safety Responsibilities of the Coatings Inspector.................................................................9-2 Inspector Medical Surveillance...........................................................................................................9-3 Safety Monitoring...............................................................................................................................9-3 Risks....................................................................................................................................................9-4 Types of Hazards.................................................................................................................................9-5 Other Hazardous Materials Encountered by Inspectors......................................................................9-9 Hazardous Environments..................................................................................................................9-10 Personal Protective Equipment.........................................................................................................9-15 Summary...........................................................................................................................................9-18
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Module 10: Navigating Coating Specifications Introduction.......................................................................................................................................10-1 Learning Outcomes...........................................................................................................................10-1 Purpose of a Coatings Specification.................................................................................................10-2 Inspecting Against a Poorly Prepared Specification.........................................................................10-4 Inspecting When There is No Specification......................................................................................10-4 Specifying Coating Systems.............................................................................................................10-5 Components of a Coating Specification............................................................................................10-8 Summary.........................................................................................................................................10-12
Module 11: Specification Review and Pre-Construction Conference; Inspection Plan Development for the Inspection of a “Bottomless” Tank Lining Installation Introduction.......................................................................................................................................11-1 Learning Outcomes...........................................................................................................................11-1
Module 12: Simulated QA/QC Inspection of “Bottomless” Tank Lining Installation Introduction.......................................................................................................................................12-1 Learning Outcome............................................................................................................................12-1 Workshop Instruction........................................................................................................................12-1
Module 13: IMO Requirements Introduction.......................................................................................................................................13-1 Learning Outcome............................................................................................................................13-2 Purpose of Standard [Paragraph 1]...................................................................................................13-2 Definitions [Paragraph 2]..................................................................................................................13-3 General Principles [Paragraph 3.1-3.333].........................................................................................13-3 Coating Technical File [Paragraph 3.4]............................................................................................13-3 Coating Standard [Paragraph 4.1-4.3]..............................................................................................13-5 Basic Coating Requirements [Paragraph 4.4]...................................................................................13-5 Coating Inspection Requirements [Paragraph 6]..............................................................................13-7 Protective Coatings Inspector Training ©2013 SSPC
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Appendix A: Comparison of SSPC and ISO Surface Preparation Standards for Power- and Hand-Tool Cleaned Steel and Blast Cleaned Steel
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Course Schedule Day One 7:30-9:00
Introduction
9:00-10:00
Module 1: Protecting Steel from Corrosion- The Role of Protective Coatings
10:00-10:15
BREAK
10:15-12:00
Module 2a: The Role of Quality Assurance and Quality Control Inspection Personnel on a Coating Project
12:00-1:00
Lunch
1:00-2:00
Module 2b: Ethics Workshop (U.S. only; other students proceed to Unit 3)
2:00-4:00
Module 3: Surface Preparation- Methods, Industry Standards and Inspection
4:00-4:15
BREAK
4:15-6:00
Module 3: Surface Preparation- Methods, Industry Standards and Inspection
Night Assignment:
Read Modules 1-5 and complete Modules 1 and 2 quizzes and Module 3 Case Study
Day Two 7:30-8:00
Module 3 Workshop A
8:00-10:30
Module 3 Workshop B
10:30-12:00
Module 4: Arithmetic for the Coatings Inspector
12:00-1:00
Lunch
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Schedule
Day Two (con’t.) 1:00-2:00
Module 4 Workshop
2:00-3:30
Module 5: Coating, Mixing, Thinning and Application: Equipment Overview and Inspection Techniques
3:30-3:45
BREAK
3:45-5:15
Module 5: Coating, Mixing, Thinning, and Application: Equipment Overview and Inspection Techniques
5:15-6:00
Review Modules 1 and 2 quizzes and Module 3 Case Study
Night Assignment:
Read Module 6-8 and complete Modules 3, 4, and 5 quizzes
Day Three 7:30-8:30
Module 5 Case Study
8:30-9:00
Module 5 Workshop A
9:00-9:30
Module 5 Workshop B
9:30-9:45
BREAK
9:45-12:00
Module 5 Workshop C
12:00-1:00
Lunch
1:00-2:30
Module 6: Industrial Protective Coatings and Coating Systems
2:30-2:45
BREAK
2:45-4:45
Module 7: Specialty Inspection Projects
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Schedule
Day Three (con’t.) 4:45-5:45
Module 8: Coating Failures and Methods of Prevention
5:45-6:30
Review Modules 3, 4, and 5 quizzes
Night Assignment:
Read Modules 9-12 and complete Module 6,7, and 8 quiz
Day Four 7:30-8:30
Module 9: Inspector Safety
8:30-9:30
Module 10: Coating Specifications
9:30-9:45
BREAK
9:45-10:45
Module 10 Workshop
10:45-11:15
Module 10 Workshop Review
11:15-12:30
Lunch
12:30-3:00
Module 11: Simulated Preconstruction Conference; Inspection Procedure Development
3:00-3:15
BREAK
3:15-4:15
Module 11: Simulated Preconstruction Conference; Inspection Procedure Development
4:15-5:00
Module 6-8 quiz review
Night Assignment:
Read ALL Modules and complete quizzes 9 and 10
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Schedule
Day Five 8:00-11:00
Module 12: Simulated Project Inspection Workshop
11:00-11:15
Review of quizzes 9 and 10
11:15-12:30
Module 13: IMO Requirements and Quiz 13, Review of quiz 13
12:30-1:30
Lunch
1:30-5:30
Final Course Exam
Day Six 8:00-2:00
Final Certification Exam
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Introduction
I
Introduction
Welcome and Course Introduction Welcome to the SSPC Protective Coatings Inspector (PCI) Training Program. The objective of this course is to thoroughly train individuals in the proper methods of inspecting surface preparation and installation of industrial and marine protective coatings and lining systems to an array of industrial structures and facilities. The course provides participants five days of intensive training and includes multiple workshops and problem solving exercises so that participants may immediately apply the learning in a classroom setting, without the pressures of production and project schedules. In order to enhance the learning environment and illustrate the importance of teamwork, the workshops and exercises will be done in small teams. The teams will be formed later during this introduction module. This course is completed with a comprehensive written examination and a practical (instrument use) examination, which will be graded by the instructors and SSPC staff. SSPC is an approved training provider through the International Association for Continuing Education and Training (IACET). Therefore, participants scoring 70% or higher on each of the examinations (written and practical) will be eligible to receive Continuing Education Units (CEUs) from SSPC through IACET.
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Effective Feb. 11, 2008, the SSPC PCI program received an American Bureau of Shipping (ABS) Certificate of Conformance stating that it is considered to be equivalent to NACE Coating Inspector Level 2 and FROSIO Inspector Level III when taught by instructors certified to either of these programs with at least two years relevant experience. This complies with IACS Procedural Requirement (PR) No. 34 Rev. 1 January 2008. Effective December 1, 2009, Lloyd’s Register, the world’s largest commercial shipping classification society, has approved SSPC’s Protective Coatings Inspector (PCI) program as equivalent to NACE Coating Inspector Level 2 and FROSIO Inspector Level III. In addition, participants can pursue certification through SSPC depending on industry experience and other prerequisites which will be described later in this introduction module.
Participation Guidelines Participants are urged to actively engage in the training by asking questions, offering relevant observations, and learning as much as possible about and from other members of their work teams. The instructors will encourage you to ask for clarifications whenever you need them. If you feel an instructor is moving over significant material too quickly, ask them to slow the pace or repeat an important point. You will find that, whenever possible, the instructors are willing to help you during breaks and over lunch, even at the end of a training day.
The Course Syllabus The following section includes a short syllabus of the thirteen modules, a description of the hands-on workshops and problem solving exercises.
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An Introduction to SSPC’s Protective Coatings Inspector Training The introduction to SSPC’s Protective Coatings Inspector Training is an orientation to the training, and as such, provides a backdrop for the course, including the history of industrial coatings as a protector of steel against corrosion and deterioration. This overview also explores other influences on the development of new industrial coating products. The relationship of quality control practices and successful coating projects is another focal point. Also addressed are the problems associated with premature coating failures, including a perspective on causes and prevention. The introductory module ends with the course learning outcomes, training participation guidelines, industry acronyms, common terminology, and a syllabus of each module. This is also the module where participants are introduced to the instructors and to each other and where housekeeping items are addressed.
Module One: Protecting Metal Surfaces From Corrosion: The Role of High Performance Coatings Module One explains how coatings protect metal surfaces from corroding. Corrosion is a process where metals give up energy and return to their natural state. Some metals have a stronger propensity to corrode than others, but all metals corrode eventually. Only four elements need to be present for corrosion to occur: an anode, a cathode, a metallic pathway, and an electrolyte. While the corrosion of metal surfaces cannot be completely halted, it can be slowed. The most widely used method to prevent/slow corrosion today, particularly on carbon steel, is the application of high performance coatings. Module One explains how today’s high performance coatings use barrier protection, sacrificial or cathodic protection, and inhibitive protection to protect modern day steel structures from the inevitable process of deterioration and decay. There is no workshop for Module One.
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Module Two: The Roles of Quality Assurance (QA) and Quality Control (QC) Inspectors on a Coatings Project Module Two compares the roles of QA and QC inspectors on coatings projects. All too often, the lines between the QC and the QA on a coatings project get blurred. When that happens, the scope of work and responsibility for that work can get blurred in the process. This module is designed to clarify the common roles and responsibilities of both the contractor’s QC inspector and the Owner’s QA inspector. This is a textbook: the way it would work in a perfect world, but it is helpful to know how things “could/should” work before getting caught up in the day to day rush of a real world coatings project. Module Two compares and contrasts the role of the QA and QC inspector on a typical coatings project. The commonalties are explored, including understanding the specification, reviewing the product data sheets (the PDS) and the material safety data sheets (the MSDS), comprehending the industry standards relevant to the specific project, documenting hold or checkpoints, and understanding paper trails. Module Two also explores the critical differences in the two roles, including issues of authority, reporting, testing, and documentation (which again, depend on the scope of work and the specification). Another issue explored by this module is the management of nonconformities.
Module Three: Surface Preparation Module Three explains the inspection of surface preparation. Preparing the surface in accordance with the specification can be the most costly phase of a coatings operation, and it is always critical to the project’s success. Surface preparation has a major focus in this training program, which covers in detail common standards used throughout the industry. The initial phase of pre-surface preparation and the inspection hold points are covered first, detailing the problems of weld spatter, edges, and repair areas. Surface preparation, which follows, covers the many methods used to clean and roughen surfaces, with a special emphasis on dry abrasive blast cleaning. The International Organization for Standardization (ISO) and SSPC: The Society for Protective Coatings have developed a series of consensus standards to govern surface cleanliness requirements. This module will explore the content of these standards including descriptions of what Protective Coatings Inspector Training ©2013 SSPC
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must be removed from the surface and what may remain on the surface for each standard. In addition to the surface preparation standards, the training will also focus on means and methods, including: blast cleaning equipment, a variety of abrasives, wet and dry abrasive blast cleaning, centrifugal blast cleaning, vacuum blast cleaning, hand and power tools, and water jetting. An overview of methods used to prepare concrete surfaces and the inspection processes involved with the preparation of concrete are included in this module. Methods for controlling the environment during surface preparation are described. The final focal points for Module Three are the common inspection checkpoints for surface preparation and the methods used to verify adherence to the specification. Module Three Inspection Case Study: Surface Preparation of the Interior and Exterior of an Elevated Potable Water Storage Tank Participants are provided with a project description that presents quality issues associated with surface preparation activities on an elevated water storage tank. Participants work in teams to address the issues from an inspector’s perspective. Module Three Workshop A: Comprehension of SSPC Surface Cleanliness Standards Participants are provided with a matrix containing various components to the written SSPC surface cleanliness standards and 14 of the 15 SSPC surface cleanliness codes. Participants complete the matrix on their own, then compare and defend answers as a team prior to revealing the team answers to the class using a team spokesperson. Module Three Workshop B: Use of Instruments, Standards and Test Kits for Surface Preparation Inspection Participants work in teams using SSPC surface cleanliness visual guides, instruments for measuring surface profile depth, light meters, and kits for assessing the cleanliness of abrasive and for assessing surface concentrations of chloride. The use of conductivity meters, and equipment for assessing dust on prepared surfaces is also included in the workshop. Participants transfer the workshop answers from the worksheets to SSPC inspection documentation forms. Data generated Protective Coatings Inspector Training ©2013 SSPC
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during the workshop is compared to specification requirements. Participants record whether the results of their inspections indicate conformance to the specification.
Module Four: Practical Arithmetic for the Coatings Inspector Module Four reviews practical arithmetic skills used by the coatings inspector. Coatings inspectors frequently need to apply basic arithmetic skills to everyday inspections. This module provides a review of common arithmetic associated with coatings inspection, including: converting percentages to decimal format; calculating area; calculating volume, converting from specific weight to percentage of thinner addition; converting VOC values; converting temperatures, and converting units of measurement for surface profile depth and paint thickness (mils to microns and back). A special session on calculating coating material quantities based on theoretical and practical coverage rates is also included in this module. Module Four Workshop: Participants are challenged with sample problems (based on life-like inspection scenarios) that require application of the arithmetic skills acquired in Module 4. A calculator is required for this workshop.
Module Five: Coating Mixing, Thinning, and Application Module Five explains the inspection of coating mixing, thinning and application. Experts claim that poor application, along with inadequate surface preparation, cause the majority of all industrial coating failures. This module will overview the various methods used to apply coatings, including conventional (air) spray, airless spray, HVLP, air-assisted airless spray, plural component spray and brush & roller. The advantages and limitations of each method, along with proper technique will be emphasized. Module Five will continue with the inspection of mixing, thinning, and coating application processes, including measuring ambient conditions, witnessing and documenting Protective Coatings Inspector Training ©2013 SSPC
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mixing and thinning procedures, wet and dry film measurements, use of the destructive gages to determine the thickness of individual layers in a coating system, pinhole/holiday detection, adhesion, and coating hardness and curing tests. The unique aspects associated with coating of concrete complete Module Five. Module Five Inspection Case Study: Application of Coatings to the Interior and Exterior of an Elevated Potable Water Storage Tank Participants are provided with a project description that presents quality issues associated with coating application activities on an elevated water storage tank. Participants work in teams to address the issues from an inspector’s perspective. Module Five Workshop A: Navigating a Coating Product Data Sheet (PDS) Participants are provided with a coating manufacturer’s PDS and a list of inquiries. Teams of participants navigate through the PDS and answer each of the inquiries. The workshop teaches where the most useful information is on a data sheet, and enforces the importance of the document and the importance of reviewing the document before a project begins. Module Five Workshop B: Use of Instruments for Coating Application Inspection Participants work in teams using instruments for: assessing ambient conditions and surface temperature; calculating wet film thickness (with and without thinner addition); measuring dry film thickness using Type 1 and Type 2 coating thickness gages; determining conformance to SSPC-PA2; measuring dry film thickness using destructive gages; detecting pinholes and holidays using low voltage holiday detectors; and measuring adhesion. Participants transfer the workshop answers from the worksheets to SSPC inspection documentation forms. Data generated during the workshop is compared to specification requirements. Participants record whether the results of their inspections indicate conformance to the specification.
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Module Five Workshop C: Identification of Coating Film Defects Color photographs of various coating defects are provided. Participants work in teams to identify the defects and their likely causes.
Module Six: Industrial Protective Coatings and Coating Systems Module Six introduces the basic components in an industrial coating: non-volatiles and volatiles. Subsequently, VOC (volatile organic compound) regulations will be explored in the context of what a QC or QA inspector should know about monitoring and reporting the addition of thinner to coating products and the actual quantity of VOC emitted into the atmosphere during application. In Module Six, participants will also learn how coatings cure. An overview of coating types and coating characteristics will be followed by key inspection concerns by specific coating type. Module Six includes an overview of common coating systems used in a number of industries including: water storage/tanks; power generation (both coal and nuclear); waste water treatment; pulp and paper; lock and dam; chemical plants; buried pipeline; food and beverage; ships/marine vessels and highway/ bridges. The unit concludes with an explanation of how coating systems are evaluated for performance.
Module Seven: Specialty Inspection Projects Module Seven describes non-routine inspection projects that can pose special challenges to the coatings inspector. Inspecting in the fabrication shop, powder coating applications, thermal spray coating (metallizing) applications, and application of liquid coatings to galvanizing (duplex system) present a different set of challenges for a coatings inspector, as does maintenance painting in the field when overcoating becomes the maintenance strategy. The unique aspects of these types of inspections are described in Module Seven. Additionally, many existing industrial structures contain coatings with toxic metal ingredients. The hazards associated with removal,
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Introduction
handling and disposal when these coatings are “disturbed” during maintenance painting operations must be controlled. The inspector may have responsibility for verifying proper set-up and maintenance of containment and ventilation systems, assuring proper worker protection, monitoring air, soil and water quality, and assuring proper handling and disposal of hazardous waste streams.
Module Eight: Coating Failures and Methods of Prevention Module Eight explains how knowledgeable coatings inspectors can help avoid coating failure. The role of the coatings inspector and the types of inspection activities that can play a role in preventing the failures are described. Case histories of actual coating failures are presented to the training group. The cause, fault and repair procedures are explored, and avoidance methods are discussed.
Module Nine: Inspector Safety Module Nine describes basic inspector safety. Fabrication shops and construction sites often pose significant safety concerns for a coatings inspector. While Module nine is not designed to provide comprehensive safety training, it makes the coatings inspector aware of potential hazards and methods of prevention. Safety issues described in Module Nine include fall prevention/protection, respiratory protection, sight and hearing protection, protection from toxic metals, and confined space entry hazards. Module Nine also describes the purpose of site-specific environmental, safety and health hazards planning and the inspector’s responsibility for personal safety.
Module Ten: Coatings Specifications Module Ten explains the purpose and content of coatings specifications. The coatings specification is the inspector’s “rule book” for a coatings project. It describes the scope of work and the requirements of the contract, as well as lists the inspection checkpoints that the inspector will be responsible for. The importance of a properly Protective Coatings Inspector Training ©2013 SSPC
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prepared coatings specification and the general layout and components in a specification are described in Module Ten. A sample specification is provided, which will be used for the Module Ten workshop, and in Modules Eleven and Twelve. Module Ten Workshop: The sample coating specification provided to the participants in Module Ten is supplemented with a series of inquiries. Teams of participants work together to navigate through the specification and locate the answers to each of the inquiries, then note the section of the specification where the information was found.
Module Eleven: Pre-construction Conference and Inspection Procedure Development Module Eleven describes the purpose and content of a pre-construction conference and explains how to prepare an inspection plan. After a careful review of the project specification during the Module Ten workshop, a preconstruction conference will be conducted. Participants are provided with an agenda of discussion items, and Product Data and MSDS for the coatings selected for the project. The course instructors represent the facility owner and the coating manufacturer, while the participants represent the inspector (QA or QC). After the pre-construction conference is completed and actions documented, the participants each develop an inspection procedure based on the project specification and any outcomes of the conference. The inspection procedure is used during the simulated coatings inspection project (Module Twelve).
Module Twelve: Project Inspection Workshop Module Twelve includes an inspection workshop which enables the participants to apply learned skills from the previous eleven modules. Inspection stations are equipped with instruments, visual guides and miscellaneous equipment and test plates. Participants work in small Protective Coatings Inspector Training ©2013 SSPC
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groups to perform inspections at each station, document the results of the inspections and compare the results to the project specification provided in Module Ten and the inspection procedures developed in Module Eleven. After all groups have completed all of the stations, the participants reconvene and discuss any problems and nonconformities observed.
Module Thirteen: International Maritime Organization (IMO) Module thirteen provides training to the coating inspector on the major requirement of the IMO PSPC (Performance Standard for Protective Coatings) MSC.215(82), “Performance Standard for Protective Coatings for Dedicated Seawater Ballast Tanks in All Types of Ships and Double-Side Skin Spaces of Bulk Carriers”.
SSPC Protective Coatings Inspector Training and Certification Program A candidate can choose one of three processes to achieve certification. Process A – Achieving Certification After Completing the PCI Course and Passing the PCI Course Exam In order to qualify for the Certification Exam under Process “A,” the candidate must successfully complete the PCI course, pass the Course Exam, have documented a minimum of 3,000 hours of coating inspection or related work experience, and possess 40 hours of SSPC or approved formal coatings training. Process B – Achieving Certification with Alternate Inspection Training The candidate seeking PCI Certification through Process “B” may take the certification exam without taking the PCI training course as long as the applicant passes the PCI Course Exam, possesses 80 hours of formal industry training approved by SSPC, of which 40 hours must be
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formal inspection training equivalent to the body of knowledge of the SSPC PCI inspection course. Candidates who have already achieved NACE III Certification or Frosio Certification can request an exemption from taking the PCI Course Exam prior to sitting for the PCI Certification Exam. In addition to possessing 80 hours of formal training, the candidate must document a minimum of 3000 hours of coating inspection or related work experience. Process C – Achieving Certification Without Formal Inspection Training The process “C” candidate is eligible to take the Certification Exam by documenting at least 7,500 hours of coating inspection or related work experience. Even though a total of 7,500 hours of documented work experience is required to sit for the PCI certification exam, a candidate seeking PCI Certification under Process “C” must document at least 5,000 hours of experience before sitting for the PCI Course Exam. Note – Examples of accepted work experience and approved training can be found at www.sspc.org. Passing Criteria This course is completed with a comprehensive written examination and a practical (instrument use) examination. Students passing both components of the PCI Course Exam at 70% or higher can take the written and practical certification exams. A passing grade of 80% or higher on the written and practical certification exam is required to become an SSPC Certified Protective Coatings Inspector. If you fail the exam or component the second time, you must wait at least six months before retaking the PCI training course and exams. Anyone who is unable to pass the written course exam, the written certification exam or the certification practical exam a third time will be considered ineligible to participate in the PCI program for a minimum of two years from the date of the last failed exam and will be required to take the PCI course again to reenter the process. Protective Coatings Inspector Training ©2013 SSPC
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PCI Renewal The PCI Basic Inspector level renewal term is four years from the initial exam date. To renew at the PCI Basic Inspector Level, the candidate must within four years take the PCI refresher course and exam and document a minimum of 750 hours of coatings inspection (or related) experience as it occurs during the four-year certification period. To renew certification for the SSPC Certified Protective Coatings Inspector the candidate must, within four years take the PCI refresher course and exam and document a minimum of 2,000 hours of coatings inspection (or related) experience as it occurs during their four years certification term. The PCI recertification exam is available online at http://www. sspcelearning.org.
Use of Materials and Textbooks All manuals given to you are yours to keep and therefore to write in. The participant workbook is written in narrative form and is augmented with PowerPoint® slides. The agenda follows this text from beginning to end. There’s space allotted to take notes in the margins. You can also use highlighters to highlight significant information. If you get lost at any point, simply ask the instructor to refer to the workbook page number that matches the information he or she is covering. You will also be given an agenda, which provides a day by day outline of the training sessions. Workshops and Quizzes are provided in a separate workbook.
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An Orientation to the Coatings Industry and Key Organizations As part of this introduction, we’d like to review several key organizations that work to organize and guide the industry toward safe, efficient, and successful coating practices: AISC ___________________________________________________ ANSI ___________________________________________________ API _____________________________________________________ ASTM __________________________________________________ AWS ____________________________________________________ AWWA __________________________________________________ CE _____________________________________________________ CSI _____________________________________________________ EPA _____________________________________________________ ICRI ____________________________________________________ ISO _____________________________________________________ NACE ___________________________________________________ NIST ____________________________________________________ NSF ____________________________________________________ OSHA ___________________________________________________ SSPC ___________________________________________________ UL _____________________________________________________ Common Industry Acronyms CFM ____________________________________________________ DFT ____________________________________________________ IAW ____________________________________________________ MSDS ___________________________________________________ MIL ____________________________________________________ NCR ____________________________________________________ PDS ____________________________________________________ POA ____________________________________________________ PSI _____________________________________________________ QA _____________________________________________________ QC _____________________________________________________ RFI _____________________________________________________ TSC ____________________________________________________
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VOC ____________________________________________________ WFT____________________________________________________ Other common terms: Micrometer (Micron) _______________________________________ Mil _____________________________________________________ Mill Scale________________________________________________ Hold point/checkpoint_______________________________________
Learning Outcomes There are sixty (60) learning outcomes associated with this training course. They are listed below. The learning outcomes pertaining to each of the thirteen modules are repeated prior to instructing the respective module. Successful completion of this course will enable participants to: 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. Protective Coatings Inspector Training ©2013 SSPC
Describe the common duties, responsibilities and the role of an industrial coatings inspector Describe the authority of a coatings inspector Explain the importance of thorough documentation Identify the elements of a corrosion cell Describe the corrosion of metal surfaces Explain how industrial coatings control corrosion Describe alternative methods used to protect carbon steel from corrosion Describe the differences between quality assurance and quality control Describe the common duties of quality assurance and quality control personnel Describe the purpose and content of a pre-job or preconstruction conference Explain the purpose of an inspection procedure/plan Explain the importance of inspection personnel Describe the importance of proper surface preparation Explain the dual objective of surface preparation Define the SSPC standards for surface preparation Describe common methods used to prepare surfaces for coating Describe methods used to control an environment during surface preparation activities Measure and record surface profile Evaluate surface cleanliness I-15
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20. Apply practical arithmetic to coatings inspection 21. Describe the procedures associated with proper mixing, thinning, and application of industrial coatings 22. Define the SSPC standards for coating application 23. Describe the role of the coating manufacturer on a coatings project 24. Use MSDS and product data sheets to verify safe and proper mixing, thinning and application of coatings 25. Describe the inspector’s role regarding coating material receipt and storage 26. Measure and record ambient conditions and surface temperature 27. Calculate wet film thickness 28. Measure wet film thickness 29. Verify the currency of calibration and assess the accuracy of nondestructive coating thickness gages 30. Measure coating thickness using nondestructive gages 31. Describe the SSPC standard for measurement of coating thickness (SSPC-PA2) 32. Measure coating thickness using destructive methods 33. Detect pinholes and holidays 34. Measure coating adhesion 35. Evaluate coating cure 36. Measure coating hardness 37. Identify common coating defects 38. Describe methods used to verify intercoat cleanliness 39. Identify basic differences between house paint and industrial protective coatings 40. List volatile and non-volatile components of a coating 41. Describe the functions of the resin, additives, pigments and solvents in a coating 42. Describe methods by which coatings cure 43. Describe the procedures used to identify service environments 44. List advantages and limitations of various generic types of industrial coatings 45. Describe functions of the primer, mid-coat and finish coat 46. Identify common coating systems used by various industries 47. Describe methods used to evaluate coating performance prior to full scale installation 48. Describe the special inspection procedures associated with shop painting, powder coatings, thermal spray coatings, and duplex coating systems 49. Describe the unique aspects of performing coatings inspection on an overcoating project 50. Describe the inspector’s role on projects involving disturbance of coatings containing toxic metals 51. Describe how coatings inspection can help prevent premature coating failure Protective Coatings Inspector Training ©2013 SSPC
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52. 53. 54. 55. 56. 57. 58. 59.
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Describe the function of a coating specification List the basic components of a coating specification List potential safety hazards associated with coatings inspection Describe the personal protective equipment used by a coatings inspector Prepare an inspection plan/procedure Perform coatings inspection on industrial projects Compare inspection results to specification requirements Apply requirements of the IMO PSPC (Performance Standard for Protective Coatings) MSC.215(82), “Performance Standard for Protective Coatings for Dedicated Seawater Ballast Tanks in All Types of Ships and Double-Side Skin Spaces of Bulk Carriers”
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Module 1 – Protecting Metal Surfaces From Corrosion: The Role of High Performance Coatings
Protecting Metal Surfaces From Corrosion: The Role of High Performance Coatings
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Corrosion Defined Corrosion can be defined as the deterioration of metallic surfaces, such as carbon steel. Corrosion is a natural process, the propensity or tendency of materials to “give up” energy and return to their natural state. While it takes tremendous amounts of energy to convert materials found in nature into usable materials for construction (like carbon steel), these materials will release that energy and convert back to their original state unless the process is stopped or slowed down.
Corrosion in Process
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The Role of Protective Coatings in Preventing/ Slowing Corrosion The most widely used method to prevent corrosion today, particularly on carbon steel, is the application of high performance, protective coatings. High performance coatings protect thousands of structures, including: off-shore drilling rigs, ships, storage tanks, sewage systems, power plants, shipping containers, pipelines, railway cars, refineries, and commercial buildings. Industrial protective coatings have been around since the 1930s, but the industry was given a boost during World War II. The need to keep ships out to sea longer and in dry dock less, led first to the development of the epoxy resin, and next to the polyamide epoxy, which had better adhesion, some flexibility, and an increased resistance to water. As the demand for the materials of war increased, the demand for improvements to industrial coatings grew with it. Better adhesion, faster cures, and better resistance to abrasion were some of the driving forces, but the need to keep materials from corroding remained the primary motivation for improvements to coatings.
The Fundamentals of Corrosion This discussion about corrosion fundamentals will focus on metals. Corrosion of metals is a natural process involving a chemical reaction – actually an electrochemical reaction, meaning that electric current is produced during the process. Corrosion will occur when four required elements are all present (note that it is assumed that oxygen is always present). If any one of the elements is missing, the corrosion process will not proceed. The required elements, which compose a “corrosion cell,” are: 1. 2. 3. 4. Protective Coatings Inspector Training ©2013 SSPC
Anode Cathode Metallic pathway (connecting the anode and cathode) Electrolyte 1-2
Module 1 – Protecting Metal Surfaces From Corrosion: The Role of High Performance Coatings
The surface of carbon steel already contains three of the four elements: the anode, cathode, and metallic pathway; only the electrolyte is missing. An electrolyte is a liquid that contains ions or “charged particles.” All salts (e.g., sodium or calcium chloride) form ions when dissolved in water. Once the electrolyte is present, the process of corrosion will proceed. To analyze how the four elements of a corrosion cell work together to produce the process of corrosion, we can use the example of a common household battery.
Dry Cell Battery - Example of Galvanic (Electrochemical) Corrosion
A corrosion cell is essentially a natural battery. The anode and its counterpart, the cathode, represent negative and positive terminals of the “battery.” During the chemical reaction process, electrical current (or electrons) flows from the anode to the cathode via the metallic pathway or connection. The electrolyte carries ions from the cathode to the anode to complete the electrical circuit. The anode (negative terminal) decays during this process while the cathode (positive terminal) remains intact or “protected.” The only difference between a corrosion cell and a manufactured battery is that the reaction process is designed to produce an electrical current for a productive use in the manufactured battery. A natural corrosion cell, however, is generally destructive since the reaction process depletes or decays the anode.
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When the anode is depleted in a manufactured battery, the reaction will stop and the battery will “die” since it can’t produce more energy. When a corrosion cell is formed on a metal surface, some areas of the metal act as the anode and other adjacent areas the cathode. The corrosion reaction will not stop so easily since the anode may have a near endless supply as corrosion (and the anode) spreads across the surface of the steel.
Illustration of Corrosion Cell - Current Flows from Anode to Cathode, Anode Decays in Electrolyte Solution
Energy Required to Convert Ores into Metals Most metals are not found in their pure state in nature, but rather as ores where they are combined with oxygen and other elements. The relative reactivity of metals is directly proportional to the amount of energy required for their conversion from ore. The chart below indicates how much energy is required to convert common metals to their pure form. Note that there are some metals that do exist in their pure form in nature such as gold, silver and copper; these metals are at the stable end of the chart.
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Common Metals
Most Energy to Convert (Less Stable)
Zinc Aluminum Cast Iron Carbon Steel Stainless Steel, Type 430, active Stainless Steel, Type 304, active Stainless Steel, Type 410, active Copper Brass Bronze Stainless Steel, Type 430, passive Nickel Stainless Steel, Type 410, passive Silver Titanium Stainless Steel, Type 304, passive Stainless Steel, Type 316, passive Zirconium Platinum Gold
Least Energy to Convert (More Stable)
Dissimilar Metals A corrosion cell can also be formed when two dissimilar metals are in contact with one another. When two dissimilar metals are connected, the metal that is higher in the chart – i.e., requires more energy to convert to a pure metal – is the one that becomes the anode and corrodes, while the other metal acts as the cathode. The physical connection between the metals serves as a metallic pathway and water or moisture typically serves as the electrolyte needed to complete the cell. The metal that acts as the anode will decay while the other “cathodic” metal remains intact. The anodic metal thereby provides “cathodic protection” to the other metal.
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Module 1 – Protecting Metal Surfaces From Corrosion: The Role of High Performance Coatings
Corrosion Versus Oxidation The corrosion of some metals does not necessarily create a problem. For example, aluminum will quickly oxidize (corrode) forming a layer of aluminum oxide on the metal surface. But the aluminum oxide layer essentially seals the metal surface and becomes protective because it stays tightly adhered and is not porous. Copper is another example of a metal the forms a protective oxide layer – in this case the characteristic green color that forms as copper weathers (known as “Patina”). For many metals, however, corrosion is a problem because the oxidation of the metal surface does not stop after an initial layer is formed. In the case of iron (and steel), a porous layer of iron oxide is formed which is loosely held to the surface. The porosity allows corrosion to continue into the iron.
Oxidation
What is Steel? When considering the corrosion of common carbon steel, we can look at iron since it is the primary component of the steel that corrodes. Steel is primarily composed of iron at concentrations from 95 to 99 percent by weight. The difference between ordinary steel and pure iron is the addition of carbon (typically up to 2 percent) and other elements. The carbon increases strength and adds other desirable properties to the metal. A variety of steel alloys can be produced by adding elements such as copper, chromium, nickel, or phosphorus (and others). Some of these additions can produce a significant reduction in the corrosion rate for particular steel alloys. One such alloy is known as “weathering steel.”
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Module 1 – Protecting Metal Surfaces From Corrosion: The Role of High Performance Coatings
Weathering Steel Weathering steels, also called high-strength, low-alloy steels (or CORTEN, a US Steel trademark), provide greater resistance to atmospheric corrosion than conventional carbon steels. In the corrosion of weathering steel, the iron oxide layer becomes protective, similar to other metals like aluminum or copper. The oxide layer of weathering steel forms differently than for ordinary steel and its appearance changes from the typical red-orange color of rust to a dark purple as the weathering process proceeds. Weathering steel is designed to remain uncoated but can be coated for additional protection. Weathering steel is not recommended for certain environments including severe industrial exposures, locations subjected to salt-water spray, or continuous submergence in water.
How Coatings Protect the Substrate from Corrosion Corrosion of metals really cannot be completely stopped. Slowing down the process as much as possible is the only option to preserve the metal and this is where protective coatings play a crucial role. Coatings are considered to function as a protective layer in three different ways: by providing barrier, sacrificial or inhibitive protection. Barrier Protection Barrier protection is the simplest way a coating functions as a protective layer and refers to the physical barrier that is formed on the substrate surface by any coating. This physical barrier prevents air and water, which are necessary for corrosion, from reaching the substrate. All coatings provide barrier protection, although some coatings have characteristics that enhance the barrier function of the coating. For example, coatings that contain micaceous iron oxide (MIO) or aluminum flakes in their formulation form plate-like layers (called lamellar pigments) in the coating film. Water or air cannot penetrate the “plates” and must take a longer path to eventually reach the substrate.
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Sacrificial or Cathodic Protection Coatings also may protect a substrate by providing sacrificial or cathodic protection. This occurs when the coating layer contains a metal that will act as the anode in the corrosion process, thereby protecting the metal substrate (or cathode). Sacrificial coatings are generally used as primers since the sacrificial metal must be in direct contact with the metal substrate. Zinc is the most common sacrificial metal used to protect iron-based steel materials. The best example of this is with zinc-rich primers where zinc dust is added to the coating formulation in amounts up to 90% by weight. A zinc layer can also be formed on a steel substrate by metallizing or galvanizing – both of which essentially deposit a solid zinc layer on the substrate. Metallizing is accomplished by melting the zinc (and/or aluminum) and spraying it onto the substrate surface using flame spray, electric arc or plasma arc processes. Metallizing can be performed in the shop or field at a project site. Galvanizing is completed by dipping steel parts in a molten zinc bath. The galvanizing process generally provides superior protection to metallizing for comparable zinc thicknesses, with the obvious limitation that it can only be done in a factory or shop setting for new steel before erection. Inhibitive Protection Some coatings also provide protection by containing inhibitive pigments that disrupt or prevent typical corrosion reactions from occurring. The mechanism by which inhibitors work is not always clear, but the common theory is that the inhibitive materials react or bind with water to prevent it from further penetrating the coating film, or produce compounds that inhibit corrosion reactions. A good example of an inhibitor is lead, which is no longer widely used in coatings since it is a health and environmental hazard. Other inhibitive pigments may include borates, chromates (which are restricted like lead), phosphates or molybdates.
Additional Cathodic Protection As previously described, coatings provide cathodic protection when a component of the coating acts as a sacrificial metal to the substrate (e.g., zinc coatings on steel). But additional cathodic protection can be provided by passive or active means. Passive cathodic protection Protective Coatings Inspector Training ©2013 SSPC
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(as with coatings) can be accomplished by attaching a dissimilar metal directly to a metal substrate to act as a sacrificial anode. Of course the other metal must be more reactive than the substrate to act as the anode and become sacrificial. To protect steel substrates or structures, zinc or aluminum are often the other (dissimilar) metals used. An example of passive cathodic protection is when sections of zinc or aluminum are attached to the underwater hull of a ship. The sections (anodes) will corrode instead of the steel thereby protecting the ship’s hull in the vicinity of the attachment points – note that multiple sacrificial anodes are typically attached over the hull’s surface. This protection is considered passive since corrosion (and cathodic protection) occurs spontaneously via the natural process. For some structures, however, the potential for corrosion can be so great that passive cathodic protection may not provide adequate protection. Such environments might included offshore platforms or buried pipeline. In these cases, active cathodic protection can be provided by applying or “impressing” an electrical current to the structure (while also using a dissimilar metal to act as the anode). In effect, the impressed current prevents the spontaneous reaction that would normally take place in a natural corrosion cell from occurring in the first place. An impressed current system requires an external power source and must be specifically designed for the structure and environment if it is to function properly. Maintenance and monitoring of the system is required.
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Summary
One definition of corrosion is the deterioration of metal surfaces. Corrosion is a natural process, the tendency of materials to “give-up” energy and return to their natural state. While it takes tremendous amounts of energy to convert materials found in nature into usable materials for construction, those same materials will readily release that energy and convert back to their original state unless the process is stopped or slowed down. Corrosion is a natural process, which involves an electrochemical reaction. In addition to oxygen, only four elements are needed for corrosion to occur: an anode, a cathode, a metallic pathway, and an electrolyte. These four elements in combination are referred to as a corrosion cell. The surface of carbon steel contains three out of the four elements; only the electrolyte is missing. Once the electrolyte connects with the surface of carbon steel, the process of corrosion will proceed. When all four elements are present, corrosion occurs at the anode, while the cathode remains intact or protected. This principle is used to create products that can protect the steel substrate (cathodic or sacrificial protection). Most metals used in construction are not found in their pure state in nature. They exist first as ores where they are combined with oxygen and other elements. The more energy used to convert these metals to usable materials, the greater the tendency to give that “energy up” and return to a natural state (ore). Carbon steel has a strong tendency to corrode, since it is “less stable” than metals like gold, platinum, and silver. The addition of certain elements during the process of creating steel can produce steel alloys with a significantly lower corrosion rate. One such steel alloy is called weathering steel or CORTEN.
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Module 1 – Protecting Metal Surfaces From Corrosion: The Role of High Performance Coatings
The most widely used method to prevent corrosion, particularly on carbon steel, is the application of high performance, protective coatings. Coatings protect metal surfaces from corrosion using three methods: barrier protection, sacrificial or cathodic protection, and inhibitive protection. All coatings provide some type of barrier protection, forming a physical barrier that prevents air and water from reaching the substrate. Sacrificial or cathodic protection is provided when a coating contains a metal which will become the anode in the corrosion process, thereby protecting the metal substrate (or cathode). Zinc is the most common sacrificial metal and is often added to primers, where the zinc can come into direct contact with the steel substrate. Pure zinc can also be melted and used to coat steel parts. The metallizing process melts zinc and uses flame spray, electric arc, or plasma arc to spray the zinc onto the substrate. Galvanizing is completed by dipping steel parts into a molten zinc bath. An additional method to provide passive cathodic protection (which is also provided by sacrificial coatings) can be accomplished by attaching a dissimilar metal directly to a metal substrate to act as a sacrificial anode (usually pieces of zinc or aluminum). The sacrificial anode will corrode instead of the steel. For some structures, including offshore platforms and buried pipeline, passive cathodic protection may not provide adequate protection. By applying (impressing) an electric current to the structure, while using a dissimilar metal to act as the anode, the current prevents the spontaneous reaction (corrosion) from occurring in the first place.
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Module 1 – Protecting Metal Surfaces From Corrosion: The Role of High Performance Coatings Module 1 - Protecting Metal Surfaces From Corrosion: The Role of High Performance Coatings
Protective Coatings Inspector Training ©2010 SSPC Protective Coatings Inspector Training ©2013 SSPC
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Module 1 – Protecting Metal Surfaces From Corrosion: The Role of High Performance Coatings Module 1 - Protecting Metal Surfaces From Corrosion: The Role of High Performance Coatings
Protective Coatings Inspector Training ©2010 SSPC Protective Coatings Inspector Training ©2013 SSPC
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Module 2a - The Roles of QA and QC Personnel on a Coatings Project
The Roles of QA and QC Inspection Personnel on a Coatings Project
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Quality Assurance vs. Quality Control Defining the Difference It is more and more common to encounter specification requirements for quality control (QC) and/or quality assurance (QA) on coatings projects. Unfortunately, it is less common for specifications to define the respective responsibilities of QC and QA personnel. All too often, the lines between QC and QA get blurred. This module is designed to clarify the roles and responsibilities of the contractor’s QC and the Owner’s QA (sometimes called a third party inspector). Quality Control (QC) is performing necessary observations, testing and documentation that verifies the work performed meets or exceeds some minimum standard as required by the project specification (also known as “inprocess” inspection). Quality control is the contractor’s responsibility. Quality control involves the routine and systematic inspection and tests that
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Module 2a - The Roles of QA and QC Personnel on a Coatings Project
are conducted to verify that each phase of the work (hold point) is in compliance with the specification. Quality Assurance (QA) is defined as the process to verify that the quality of work performed is actually what was reported by quality control. Quality assurance is typically performed by the Owner (e.g. facility project engineer) or a third party on behalf of the Owner. Quality assurance is more of an audit function, used to verify that the quality control is being performed, but may include conducting actual testing on a spot or periodic basis. In simple terms, quality assurance by the Owner is meant to verify that the quality control implemented by the contractor meets the requirements of the specification.
Inspection of Dry Film Thickness
A coatings inspector can represent a variety of entities, and can serve different roles based on the contractual relationships listed below. 1.
The coatings inspector can perform quality control for the painting contractor (hired as a consultant on a contract basis, or as an SSPC QP5 certified inspection agency hired on a contract basis). The QC inspector may not have the authority to direct the contractor employees, but may report nonconformities to the appropriate personnel for action.
2.
The coatings inspector can perform quality control for the painting contractor, as a member of the contractor’s staff.
3.
The coatings inspector can perform quality assurance for the prime contractor who is subcontracting the painting work to one or more painting contractors.
4.
The coatings inspector can perform independent, third party quality assurance for a facility owner.
5.
The coatings inspector can perform independent, third party quality assurance for the coating supplier (e.g., single source responsibility projects or warranty work).
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Module 2a - The Roles of QA and QC Personnel on a Coatings Project
Authority Roles The distinction between Owner QA and third party QA is critical. When the Owner performs his own QA (with direct staff), he has a contractual relationship with the contractor, and therefore can exert control through the contract (or by withholding payment) when the operations are out of compliance. However, when an Owner subcontracts third party QA, the third party QA does not have a contractual relationship with the contractor; therefore, third party QA typically can only advise and document the non-conformities of the contractor’s operations and advise the contractor’s QC, other contractor management staff, or the Owner. Both the Owner and the third party QA representatives must be careful not to unduly interrupt contractor operations due to potential legal liability or contract issues regarding control of the work and costs related to work stoppages (often referred to as delay or disruption). Both QC and QA are necessary components to verifying specification compliance. Most specifications and contract law make it clear that the Owner (or third party) performing QA on a project does not relieve the contractor of the responsibility of performing QC and meeting contract requirements. The International Standards Organization (ISO) advocates the use of both QC and QA to achieve a total quality system. Hold Point Inspection The specific duties of the QC and the QA will vary from project to project. The coating inspection process typically dictates that after certain activities (e.g. surface preparation), work should be halted, inspected, rework performed as necessary and accepted by the QC and QA, before the contractor can move on to the next step of the painting process. These specific inspection items are typically referred to as “hold points.” Hold point inspections can involve visual observations or tests and the results must be documented. In broad terms, hold point inspections are typically performed during: 1. pre-cleaning 2. surface preparation 3. primer application 4. intermediate coat application 5. top coat application 6. cure Protective Coatings Inspector Training ©2013 SSPC
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Module 2a - The Roles of QA and QC Personnel on a Coatings Project
Hold point inspections will be discussed in more detail later. A rule of thumb is that the QC inspection should occur first and any non-conforming items identified by the QC should be corrected, reinspected and accepted by the QC. The QA observations should only occur after the work (hold point) has been accepted by the QC. The QA should then verify that the work that the QC accepted meets the requirements of the specification. If the QA identifies non-conforming items, they should be repaired and re-inspected before the QA accepts the work and the contractor proceeds to the next step of the painting process. It is often helpful, if not necessary, to have the QC or foreman present during the QA observations, so that any deficiencies can be identified and confirmed by both parties. This also allows the contractor to clearly identify areas requiring rework to his workers. The QA process typically includes both a review of tests or documentation provided by the QC and duplicate QA testing of certain hold points (e.g. dry film thickness measurements) as an audit function to verify that the results reported by the QC are accurately reflecting the conditions of the work. When results of QC and QA differ, the QA observations typically supersede those of the QC. The actual resolution of differing QC and QA observations should be discussed and agreed upon in the pre-construction conference. Roles of QA and QC Historically, when the coating inspection concept began to evolve in the 1970s, there was little distinction between the roles of QC and QA. Most early coating inspection was performed as a response Protective Coatings Inspector Training ©2013 SSPC
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Module 2a - The Roles of QA and QC Personnel on a Coatings Project
to the inspection parameters established in the nuclear power plant construction industry and ANSI/ASME N45.2.6, Qualification of Inspection, Examination and Testing Personnel for Construction Phase of Nuclear Power Plants. ANSI N45.2.6 defined the coating inspection tasks that were required during installation or maintenance of nuclear facilities. They specifically applied to third party inspectors retained by the Owner, performing hold point inspection of contractor activities. As coating inspection expanded beyond the nuclear arena and into other industry segments like transportation and water storage, most Owners continued to rely on a third party inspector to verify that contractor activities were performed according to the specification. That is, the Owner’s representative performed all testing of the coating inspection hold points. In the 1990s and 2000s, Owners began to recognize that while third party inspection was still desirable, it was not intended to replace QC by the contractor. With the increased recognition of ISO, SSPC QP1 and other certifications, more and more companies are moving to the concept of a total quality system involving a clear division between QC and QA responsibilities. In many cases, although it is intended that Contractor’s QC conduct first line inspections, Owners are not specifically establishing the QC requirements in the specifications, or are not enforcing the requirements when they do exist. As a result, QA is frequently faced with taking on the responsibility for inspecting and accepting the work. When the roles of QC and QA are not defined, this results in the loss of a critical component of a total quality system and often creates a confrontational position between the QA and the contractor. On the other hand, when the QC and QA both perform their respective roles during the painting process, the process results in a quality coatings project. Due to the improving understanding of quality systems, more and more organizations and end users are attempting to better define their expectations for both the QC and QA. Organizations Defining QC and QA Responsibilities There are several organizations that have established standards, minimum training and experience requirements, and certification for individuals and companies associated with the inspection (QC or QA) of coatings projects. Protective Coatings Inspector Training ©2013 SSPC
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Module 2a - The Roles of QA and QC Personnel on a Coatings Project
The Society for Protective Coatings (SSPC) Painting Contractor Certification Program (PCCP), specifically QP-1, establishes specific requirements for the qualifications and duties of the contractor’s QC. While the specific duties of the QC are not specifically defined in the SSPC QP-1 standard, the supporting documentation required by the program (i.e., QC program, audit criterion) provides a framework for the required QC inspections. The SSPC QP-1 program states that hold point inspections should be performed during six primary stages of the coatings project. That is pre-cleaning, surface preparation, primer application, intermediate application, top coat application and cure. The SSPC QP-1 Annual Internal Audit Report / Checklist for SSPC Certified Contractors (Rev 02/04), specifically requires that the QC representative prepare daily reports that include the following information (at minimum): 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12.
compressed air cleanliness dry film thickness air temperature humidity dew point temperature surface temperature abrasive cleanliness degree of cleanliness achieved surface profile batch numbers of paint used batch numbers of thinner used mixing according to specification
The SSPC Publication, “The Inspection of Coatings and Linings, A Handbook of Basic Practice for Inspectors, Owners, and Specifiers,” 2nd Edition (SSPC 03-14), Chapter 3, Quality Control for Protective Coatings Projects, features a series of coating inspection forms. These help establish the inspections that should be performed and documented by the contractor’s QC. The SSPC QP-5 program, “Standard Procedure for Evaluating the Qualifications of Coating and Lining Inspection Companies,” establishes a certification for inspection companies whose focus is Protective Coatings Inspector Training ©2013 SSPC
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Module 2a - The Roles of QA and QC Personnel on a Coatings Project
the industrial coating and lining industry. It evaluates an inspection company’s ability to provide consistent quality inspection of coatings & linings for its clients (typically QA). While it establishes the minimum training and experience requirements of third party inspectors, it does not delineate the specific duties of a QA inspector or inspection company providing third party inspection. Under this certification, the duties of the third party QA inspector are defined as those specified or contracted by the Owner. ANSI/ASME N45 2.6 establishes criteria for companies to internally certify individual coatings inspectors through experience, education and testing as Level I, II, or III nuclear coating inspectors. The SSPC QP-5 program relies on similar levels of experience and training for confirming qualifications of third party inspectors.
Pre-construction (Pre-job) Conference The pre-job conference typically occurs prior to project start-up and should be attended by representatives of the contractor, coatings suppliers, Owner’s representatives and third party inspectors. If you are the QC or QA you should attend this meeting. Too often the prejob conference is attended by management and the on-site QC and QA do not participate. If this is the case, make sure you identify any questions, unclear items or discrepancies with the person who will be attending the meeting. Obtain and review a copy of the pre-job conference meeting minutes to determine what, if any, clarification was agreed upon. Prior to the pre-job conference, both the QC and QA should critically review the specification and be prepared to discuss any discrepancies, missing, incomplete, unclear or ambiguous items in the specifications. When both QC and QA will be used on the project, the duties, responsibilities and reporting requirements should be clearly discussed and agreed upon by all parties. The pre-job conference should provide a review for all parties on the organizational structure and representatives of each stakeholder (i.e., owner, contractor, third Protective Coatings Inspector Training ©2013 SSPC
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Module 2a - The Roles of QA and QC Personnel on a Coatings Project
party inspector, coating manufacturer’s representatives). This should include the title and responsibilities of each person as well as their reporting relationship within the company or organization. The pre-job conference should summarize the contractor’s approach to the project including: schedule, location(s) of equipment, and manpower estimates. The pre-job conference should review the specification and sequence of work, address any specification discrepancies, and discuss how QC and QA inspections will be coordinated and implemented. It should include discussion of preparation of test sections (i.e. job reference standards), if required; adequate lighting; inspector safe access; inaccessible areas; and other project-specific considerations. The final phase of the pre-job conference should include a discussion of all required QC and QA documentation and submission schedules. The Owner should also address the procedure that should be followed if there are discrepancies in the QC and QA documentation. A sample agenda for a pre-job conference is shown below. 1.
Contractor’s Proposed Operation, Including Equipment and Personnel A.
Compliance programs i. QC program ii. Worker Protection Program iii. Environmental Protection Program iv. Containment Program v. Waste Management Program B. Location of Equipment i. Dust collector ii. Hygiene facilities iii. Recycling equipment (on or off site) iv. Waste storage C. Work schedule 2.
Inspector Safety & Proper Access A. Safety lines, lifts, ladders B. Use of hygiene facilities
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C. 3.
Protective clothing & HEPA vacuum
Inspection & Measurement A. Discuss inspection holdpoints B. QC inspections C. QA inspections D. Procedures for resolving discrepancies
4.
Inaccessible areas (identified and addressed)
5.
Lighting
6.
Product Information A. Verify availability of PDS/MSDS B. Review abrasive, coatings systems, mixing & thinning requirements
7.
Visual Standard A. Pre-blast standard (if specified) B. Review SSPC VIS Standards and definitions for specified surface preparation
Attendees should be listed on a sign-in sheet circulated at the start of the meeting. All items discussed at the pre-job conference should be recorded in the form of minutes and distributed to all attendees of the meeting. Any specification clarifications should be transmitted to all affected parties. A pre-construction conference will be conducted later in this course.
Development of an Inspection Procedure (Plan) Project specifications can often be complex and contain many details unrelated to surface preparation and painting. As a result, locating the inspection check points can be cumbersome and time consuming. More consequential, key inspection checkpoints may be overlooked. The development of an inspection procedure before the project begins can aid the inspector in identifying the inspection checkpoints and the associated acceptance criteria. Protective Coatings Inspector Training ©2013 SSPC
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There is no standard format for an inspection procedure. A table or chart format is often the most effective and easiest to complete. A chart containing three columns is usually adequate. The header of the first column is “Inspection Checkpoint. The column is populated by copying each inspection checkpoint associated with surface preparation and coating application listed in the project specification. The header of the middle column is “Inspection Method” and lists the inspection instruments, visual standards or other equipment needed to perform the inspection. Note that in some cases the word “visual” is used, since some coatings inspection is only done visually, with no specific instrumentation (for example, verifying proper installation of protective coverings). The final column header is “Acceptance Criteria” which is established by the project specification. An example of an inspection procedure chart is shown below, along with two sample entries. A complete inspection procedure will have many entries and may consume several pages. You will be developing a complete inspection procedure in Module 11 of this course. Sample Inspection Procedure Inspection Checkpoint
Inspection Method
Acceptance Criteria
Surface Profile
Testex Replica Tape
2.0-3.5 mils
Surface Cleanliness
SSPC VIS 1
SSPC-SP10
Forms containing additional columns to record the ASTM or SSPC standard or method employed to conduct the inspection check point, the method used to verify instrument accuracy, the number of measurements required and the report form where the information should be recorded may be required on certain projects. Work Plans and Process Control Procedures Many specifications require the contractor to prepare project-specific work plans or process control procedures (PCPs) and submit them to the facility owner for review and approval prior to commencing work. Work plans may be contract-specific or may be more general and used by the contractor to both plan and control the work process. A Work Plan covers all of the individual phases of a project, including both production and inspection. Ideally separate work plans should be developed for each phase of a project, if the scope of work differs. A Work Plan is merely a compilation of all of the individual processes Protective Coatings Inspector Training ©2013 SSPC
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Module 2a - The Roles of QA and QC Personnel on a Coatings Project
that make up the specified work. There is no prescribed format, as long as the plan is complete, accurate and useable. The work plan should include a description of the processes that will be employed, including any of the critical factors that have a direct bearing on quality and safety. They should reference the project specification and include acceptance/rejection criteria and the authority required for approval of non-conformities. The plan includes a project schedule based on major phases of the work scope, and lists the equipment, mobilization plans, work area layout, and the receipt, storage and control of materials. It should also describe the frequency and content of personnel meetings to be conducted throughout the project. A sample pipe line specification listing the content of a coating work plan (specifically section 1.4.2.1) is appended to this module. Process Control Procedures or PCPs are contract-specific and require formal approval before work can begin. In some cases, the PCPs are required to be submitted in a pre-approved format. PCP’s typically include the following items: 1. 2. 3. 4. 5. 6. 7. 8. 9.
Date, Procedure No., Revision No. and Description of the Contract Work Item List of contractors, subcontractors and attached documents/ references Descriptions of qualifications and certificates to perform the work scope Process descriptions and list of equipment required to conduct the work scope Inspection plan, including instruments, calibration requirements, references to standards and acceptance criteria Copies of forms/records to prove conformance Authority required for approval of non-conformities Worker safety requirements Environmental protection controls and waste management procedures
The QA inspector may be asked to review the contractor’s work plans or PCPs for completeness and conformance to the requirements of the project specification. Work Plans or PCPs should be submitted well in advance of the intended project start date, as they must typically be reviewed, approved (or revised, reviewed and approved) prior to commencement of any production activities. The PCP content for Navy/military contracts is appended to this module. Protective Coatings Inspector Training ©2013 SSPC
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Module 2a - The Roles of QA and QC Personnel on a Coatings Project
Documenting and Reporting Procedures One of the most important responsibilities of a coatings inspector is to document the results of the inspections in a clear, concise, and timely manner. Oftentimes measurements and readings are recorded in an inspector logbook, then transferred onto inspection forms. Without timely, formal documentation, many of the key results may be lost or forgotten. It is acknowledged that few individuals enjoy paperwork. However, it is a necessary evil in today’s litigious culture. Documentation of specific, key items as the work progresses may do nothing more than fill a file cabinet once the project is completed. However, in the event of a problem, it can provide key information for resolution of the problem. Documentation of the results of inspections can also be a key element in the event that the coating failure results in litigation against the coating contractor or the coating supplier. Just like homeowner or car insurance, you may never use it, but when you need it, you’re glad you have it. There is no “standard inspection form” that every inspector uses. The design and content of the documentation forms can vary, and may be customized to a project. It is important that the form ultimately used by the inspector address all of the inspection checkpoints included in the project specification and the precise location of the area inspected, and that the form allow ample space for commentary. Chapter 3, “Quality Control” of the SSPC Handbook: The Inspection of Coatings and Linings contains seven forms that may be adopted by inspection personnel. Copies of these forms are included at the end of this module; some will be used in the workshops later on in this training course. Form 1: Documentation Acknowledgement Documents an individual’s acknowledged receipt of specifications, revisions to the specification, project correspondence, reports, test results, drawings and other written documents. Form 2: Inspection Equipment Calibration Record Documents that the calibration of inspection equipment was performed and is current.
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Module 2a - The Roles of QA and QC Personnel on a Coatings Project
Form 3: Inspection Equipment Issuance Record Documents an inspector’s receipt of inspection instruments and standards and acknowledges responsibility for maintenance and care of the equipment. Form 4: Daily Coating Inspection Report Documents the results of any QA and QC inspection checkpoints after a pre-surface preparation inspection, during and after surface preparation, ambient conditions, and during and after coating application. Dry film thickness values are recorded on Form 5. Form 5: Dry Film Thickness (DFT) Measurement Worksheet Documents the spot and area coating thickness measurements. Form 6: Corrective Actions Report Documents any nonconforming items and addresses proposed and required corrective actions for each nonconformance. Form 7: Photographic Record Documents the location and area of any photographs acquired during inspection of surface preparation and coating application. Note that the form currently reflects the use of print film. With the widespread use of digital photography, the form may be obsolete or even unnecessary. In addition to inspection records, the inspector should maintain a project logbook or “diary” that contains narrative, daily entries regarding what operations were performed, progress, and any other project-related “events” that occurred. Each entry should contain the date and start with, “The writer arrived on-site at (time)....” Note that the diary is “discoverable” during the litigation process.
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Paint Inspection Documentation Acknowledgement Project:
Copy to:
Project #:
Location:
Office
Estimating
QC Sup
HSO Inspector
Company Name:
Start Date:
Proj Mgr
Contact:
Finish Date:
Other
This is to acknowledge receipt of one or more of the following documents: Specifications
Revisions
Correspondence
Drawings
Test Results
Other
Reports
Receipt of all documentation is to be recorded in the project documentation log Date
Documentation, Specifications, Prints, and Revisions
Description and Title
Update all specifications and procedures and record in appropriate revision logs Issued to:
Company:
Receipt Acknowledge by:
Signature:
Date:
Return this form with signature to:
SSPC QCS 2-01 Revision 1 09/2005
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Module 2a - The Roles of QA and QC Personnel on a Coatings Project
Inspection Equipment Calibration Record Project:
Copy to:
Case #:
Location:
Office
Issued to:
Inspector Return Date:
Issue Date:
Other
Document all equipment requiring calibration Type/Model
Serial #
Other Date of Calibration
Calibration Requirements
Calibration Performed by
Calibration Due Date
SSPC QCS 2-12 Revision 1 09/2005
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Inspection Equipment Issuance Sheet Project:
Office
Copy to:
Case #:
Inspector
Issued Date:
Calibration Certificates
Location: Attachments: Issued to:
Returned Date:
Issued by:
Calibration Records
Inspection Equipment Item
Model #
Serial #
Environmental Conditions
Operation Procedure
Date of Calibration
Calibration Verification
Surface Preparation
Application
Standards and Specifications
The following desginated inspector has been issued the above listed inspection equipment, certifications, and calibration standards required to perform the intended inspection as required by contract. The inspector is required to keep all issued equipment in a safe place and in good working order. The inspector will document required calibrations and maintain all records per job specifications. Upon completion of the project, the inspector will return all equipment to the QC manager. The inspector is responsible for negligence and understands and accepts to replace damaged or stolen equipment. Issued by:
Issued to:
QC Manager Signature:
Inspector Signature:
Date:
Date:
SSPC QCS 2-13 Revision 1 09/2005
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Module 2a - The Roles of QA and QC Personnel on a Coatings Project
Paint Inspection Daily Coating Inspection Report
Date: Project #:
/
/
Su M Tu W Th F Sa
Pg
of Copy to:
Inspector:
Owner
QC Super
Project/Client:
Contr
Location:
Attachments:
Description:
DFT Sheet
NCR/CAR
Requirements: Contractor:
Spec #:
Description of Areas and Work Performed
Revision #:
Hold Point Inspections Performed
1. Pre Surface Preparation/Condition and Cleanliness 2. Surface Preparation Monitoring 3. Post Surface Preparation/Cleanliness and Profile 4. Pre Application Prep/Surface Cleanliness 5. Application Monitoring/Wet Film Thickness (WFT) 6. Post Application/Application Defects 7. Post Cure/Dry Film Thickness (DFT) 8. Nonconformance/Corrective Actions Follow-Up 9. Final Inspection
Surface Conditions
New
Maint
Steel
Galvanize
Hazard
:
Other
Dry Bulb Tempº (C/F)
º
º
º
º
Wet Bulb Tempº (C/F)
º
º
º
º
Fe
ppm
%
% Relative Humidity Surface Tempº (C/F) Min/Max
pH
Scale
Pitting/Holes
Crevices
Sharp Edges
Wind Direction/Speed
Weld
Moisture
Oils
Other
Weather Conditions
Abrasion
Handle
Recoat
Runs/Sags
Pinholes
Fall Out
Other
Surface Preparation
Finish Time:
Solvent Clean
Est Sq Ft:
Hand Tool
HP Wash PSI
Power Tool Other
Abrasive Blast
Abrasive Type
Sample
Blast Hose Size
Nozzle Size/PSI
Air Supply CFM
Air Supply Cleanliness
Water/Oil Trap Check
Equipment Condition Check
Job Specification
SSPC/NACE SP
SSPC/NACE Spec/Visual Stds Profile Check
Disc
Specified
Tape
mils avg/Achieved
Surface Effect on DFT Gage/BMR
Gage mils
mils
Dry Film Thickness (DFT) Gage Calibration Record
Gage Type/ Model
Gage Serial #
Plate/Shim Mils/µm
Gage Adj +/–
Spec Avg DFT
Finish Time:
Primer
Intermediate
DFT Last Coat
DFT This Coat
%
º
/
º
Mix Ratio:
Prod Name:
Mix Method:
Prod #:
Strain/Screen:
Color:
Material Temp:
Kit Sz/Cond:
Sweat-In Time:
Shelf Life:
Pot Life:
ºF Min/Hrs Min/Hrs
Reducer #:
Pt/Qt/Gal
Qty Added:
%
(B)
% by Vol:
(C)
Specified WFT Avg:
Reducer:
Achieved WFT Avg:
Airless/Conv Spray
Brush Hose Diameter:
Roller
Mils Mils
Other Air Check:
Ratio/Size:
Hose Length:
SEP/Trap:
GPM/CFM:
Spray Gun:
Filter:
PSI:
Tip Size:
Agitator:
Inspector Signature:
º º
Touch-Up
Qty Mixed:
Pump Pot:
% /
Est Sq Ft:
Topcoat
Mfr:
Batch #s
º º
Generic Type:
(A)
Surface Cleanliness and Profile Measurement
/
Application
Start Time: Holidays
%
º º
Painted Surface Condition:
Start Time:
/
Dew Point Tempº (C/F)
Dry/Over Spray
:
Concrete
µg/cm2 (µs/cm)
Touch
:
Time (Indiciate AM or PM)
Degree of Corrosion:
Dry to:
:
Age/Dry/Cure
Sample Report #
Cl
Ambient Conditions
Primer/Paint
Degree of contamination: Test:
Approved by:
Date:
SSPC QCS 2-06 Revision 1 09/2005
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Paint Inspection DFT Measurement Worksheet
Date:
/
/
Su M Tu W Th F Sa
Project #:
Pg
of Copy to:
QC Super
Inspector:
Contr
Project/Client: Location:
Spec #:
Description:
Revision #:
Item: Location
Area
Item: Location
Spot Readings 1
2
3
Total
% Min/Max
A
B
C
C
Specified DFT
mils/µm
Total avg
mils/µm
for application record
Area 2
3
Item: Location
Total
% Min/Max
Avg
% Min/Max
Avg
C D
E
E mils/µm
for application record
Area
3
Total
A
Specified DFT
Avg
C
D
D
E
E
Reference Inspection Report #
Total avg
mils/µm
for application record Gage Adj +/–
Spec Avg DFT
Specified DFT
Reference Inspection Report #
DFT Gage Calibration Record Plate/Shim Mils/µm
Approx Sq Ft
% Min/Max
Total avg
Avg
mils/µm
for application record
2
3
Total
A
C
mils/µm
Spot Readings 1
B
mils/µm
Total
mils/µm
Area
B
Specified DFT
3
Reference Inspection Report #
Spot Readings 2
Approx Sq Ft Item: Location
% Min/Max
2
A
D
Total avg
Total avg
for application record Spot Readings
1
C
mils/µm
mils/µm
Area
B
Specified DFT
Gage Serial #
Specified DFT
B
1
Gage Type/ Model
Approx Sq Ft
Reference Inspection Report #
Spot Readings
Reference Inspection Report #
Approx Sq Ft
Total
E
A
Item: Location
3
D
1
Approx Sq Ft
2
A
B
Reference Inspection Report # Item: Location
Spot Readings 1
E Approx Sq Ft
Area
Avg
D
Owner
mils/µm
% Min/Max
Total avg
Avg
mils/µm
for application record
Comments: DFT Last Coat
DFT This Coat
Inspector Signature:
Date:
SSPC QCS 2-07 Revision 1 09/2005
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Paint Inspection Corrective Actions Report
Date:
/
/
Su M Tu W Th F Sa
Project #:
Pg
of Copy to:
QC Super
Inspector:
Owner
Contr
Project/Client: Location:
Attachments:
Stop Work Order
Description: Requirements: Contractor:
Spec #:
Time and Location
Name/Company/Title
Revision #:
Description of Nonconformance Item
Description of Nonconformance
Referenced Spec/Procedure/Standard
Action Level
Discussion and Recommendations
Approval and Corrective Actions
Corrective Actions Follow-Up
Final Approval
Authorized Contractor Signature: Title:
Inspector Signature:
Date:
Date:
SSPC QCS 2-08 Revision 1 09/2005
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Paint Inspection Photograph Record
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Exposures: Roll/Disc #: Comment
Inspector Signature: Date: SSPC QCS 2-10 Revision 1 09/2005
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2b
Ethics
Ethics The ethics of the coating inspector has come under increasing awareness in the wake of the more widespread investigations into painting programs. Recent statewide investigations of several Transportation Agencies, contractors and third party inspection agencies have led to the highest level of scrutiny of the ethics of all of the parties. Ethics is defined as “motivation defined by the ideas of right and wrong.” The legal definition of ethics is “of or relating to moral action and conduct; professionally right; conforming to professional standards.” Regardless of whether the coating inspector is functioning as QC or QA, the inspector must have a high level of personal integrity and a strong work ethic to provide quality monitoring of the project and a fair accounting to all involved parties. The inspector should not impose personal standards of quality or work, and must remain constantly aware that the criteria for work acceptance are the specification requirements. While some obvious examples of ethical breaches would include blatant fraud, falsification of documentation, acceptance of bribes or gratuities, etc., there are also several ethical breaches that are not as clear.
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Documentation Completion of inspection reports documenting activities that are not true is an ethical breach. For example, if an inspector records on the report that “SP-10 (near-white blast) was achieved,” but subsequent inspection of the surface indicates the level of surface preparation is a SP-6 (commercial blast), the report could be treated as fraudulent. Signatures on inspection reports that contain incorrect information or indicate that tests were performed that were not actually performed by the report signer, can be treated as fraudulent. Recording inspections or tests performed by someone else as testing performed by the inspector, can be considered fraudulent. Recording observations, tests or conditions as “acceptable” when they do not meet the specification is considered unethical. Time and Expense Reports Charging time to a project that was not actually spent performing work activities on the project is unethical. Padding (i.e. adding additional expenses such as increased mileage or time) on time or expenses reports, is considered fraudulent and unethical. Gifts If you work for an owner or engineering firm, your company probably has a policy on accepting “gifts.” Many companies do not permit their staff to accept any form of gift or gratuity. Cash, loans, airline tickets should never be accepted from any party. Additionally, loans of equipment for personal use, work performed for the inspector at his or her home by the contractor, or any other exchanges of goods, services or materials between the contractor and inspector are all likely ethical breaches. In some recent investigations, discussion of personal finances (e.g., “I’m really having trouble making ends meet…”) have been construed as a solicitation for a bribe.
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Module 3 - Surface Preparation: Methods, Industry Standards and Inspection
Surface Preparation: Methods, Industry Standards and Inspection
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Introduction Preparing the surface according to the specification can be the most costly phase of a coatings operation, and it is always critical to the project’s success. Surface preparation has a major focus in this training program, which covers in detail common standards used throughout the industry. The initial phase of pre-surface preparation and the inspection are covered first, detailing the importance of a concrete condition survey, the problems associated with voids, surface irregularities, surface protusions, excessive surface profile and cracking. Surface preparation, which follows, covers the many methods used to clean and roughen surfaces. ISO Standard 8502, “Preparation of Steel Substrates before Application of Paints and Related Products -- Tests for the Assessments of Surface Cleanliness” describes all of the ISO standards associated with surface preparation. SSPC: The Society for Protective Coatings has developed a series of consensus standards to govern surface cleanliness requirements. Currently, there are thirteen consensus SSPC standards for surface preparation. ISO and SSPC standards will be explored, including descriptions of what must be removed from the surface and what may remain on the surface for each standard. In addition to the surface preparation standards, the training will also focus on means and methods, including: blast cleaning equipment, a variety of abrasives, wet and dry abrasive blast cleaning, centrifugal blast cleaning, vacuum blast cleaning, hand- and power-tools, and water jetting. The final
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focal points for Module 3 are the common inspection checkpoints for surface preparation and the methods used to verify adherence to the specification.
Module 3 Learning Outcomes Successful completion of Module 3 on Surface Preparation: Methods, Industry Standards and Inspection will enable the participant to: 1. 2. 3. 4.
Describe the importance of proper surface preparation Explain the dual objective of surface preparation Define the standards for surface preparation Describe methods used to control an environment during surface preparation activities 5. Describe common methods used to prepare surfaces for coating 6. Measure and record surface profile 7. Evaluate surface cleanliness
Overview Preparing the surface for subsequent application of the coating system is the most critical (and typically the most expensive) step in an industrial coatings project. Whether the surface is plastic, glass, wood, concrete, masonry, aluminum, carbon steel or stainless steel, surface preparation (cleaning and roughening the surface) remains a key factor in determining the ultimate service life of the applied system. In general terms, the better the surface preparation, the longer the life of the coating system. However, not all surfaces or service environments (the environment that the coating system must perform in; for example immersion, atmospheric, chemical, etc.) and not all coating systems demand the same degree of surface preparation. That is, a facility owner may be able to economize his maintenance painting program by specifying a lower degree of cleaning AND choosing a coating system that is designed to perform over a lesser degree of surface preparation while still providing long-term protection in the service Worker Abrasive Blast Cleaning environment. For example, potable water Protective Coatings Inspector Training ©2015 SSPC
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storage tank owners often specify a higher degree of cleaning for the interior liner compared to the exterior surfaces, since the interior environment (immersion) is more severe. While a higher degree of cleaning on the exterior may lengthen the life of the coating system, the increased cost associated with the higher degree of cleaning may not justify a moderate increase in service life.
The Inspector’s Role The inspector’s role related to pre-surface preparation is multi-fold, and may vary from project to project. For example, on most projects, the inspector is typically responsible for verifying that structural deficiencies have been repaired and that the contractor’s equipment is operating properly and productively, so that the project remains on or ahead of schedule.
Purpose of Surface Preparation The purpose of surface preparation is two-fold: to clean and to roughen the substrate according to the requirements of the specification. Sometimes the methods used to prepare surfaces for coating application achieve these criteria simultaneously (as with abrasive blast cleaning), while other times these steps must be performed separately (as with chemical stripping). In either case, the inspector must treat these as two distinct “acceptance criteria,” as the level of cleaning may be adequate, but the roughness may be insufficient or excessive. Alternatively, the surface roughness may be on target, but the level of cleaning may be inadequate.
Inspection of Surface Preparation As we discussed earlier in this module, surface preparation is perhaps the most important factor in determining the success (or failure) of a protective coating/lining system. It stands to reason then that the inspection processes associated with surface preparation are also very critical. Once the primer is applied to the prepared surfaces, it is nearly impossible to determine the level of surface cleanliness and surface profile depth that was achieved. Therefore, the inspector must observe Protective Coatings Inspector Training ©2015 SSPC
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the surfaces before the primer is applied. Otherwise, the coating will need to be removed, adversely impacting the project costs and schedule. There are several “inspection checkpoints” associated with surface preparation. Not all of these checkpoints are invoked by every project specification. For example, if the specification requires power tool cleaning (SSPC-SP 3), then measurement of surface profile depth, an abrasive cleanliness check and a compressed air cleanliness check are not necessary. The most common inspection checkpoints associated with surface preparation include: 1. 2. 3. 4. 5. 6. 7.
Measuring ambient conditions prior to final surface preparation Conducting a compressed air cleanliness (blotter) test Measuring blast nozzle air pressure and nozzle orifice size (described earlier) Conducting an abrasive cleanliness test Assessing surface cleanliness Measuring surface profile depth Verifying surfaces are ready for primer application
Each of these seven can involve multiple checkpoints. The procedures used to perform the various checkpoints (including the proper instruments/visual guides and reference photographs) are described below.
Review of Industry Standards The American Society for Testing and Materials (ASTM) and the National Association of Corrosion Engineers (NACE International) both have standards for measurement of surface roughness (profile) after abrasive blast cleaning. ISO, SSPC (The Society for Protective Coatings), and NACE International have standards for surface cleanliness. Industry Standards for Measuring Surface Profile Depth The ASTM standard for measurement of surface profile (ASTM D4417, “Test Methods for Field Measurement of Surface Profile of Blast Cleaned Steel”) prescribes three methods of measurement, while NACE SP0287 describes only one method. These methods of Protective Coatings Inspector Training ©2015 SSPC
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measurement will be described later in the module. It is important to recognize that these standards simply describe how to procedurally conduct a test; they do not provide an acceptance criterion. Therefore, the specification writer must state the acceptable surface profile range. SSPC PA 17, Procedure for Determining Conformance to Steel Profile/ Surface Roughness/Peak Count Requirements describes a procedure suitable for shop or field use for determining compliance with specified profile ranges on a steel substrate using Methods A (visual comparator), B (depth micrometer) and C (replica tape) as described in ASTM D 4417, and the portable stylus instrument method used to determine surface roughness and peak count as described in ASTM D 7127. In many cases, the coating manufacturer will recommend/specify the range of the surface profile depth for a given coating system on their product data sheet (PDS). If this information is not listed on the PDS, a technical representative of the coating manufacturer should be contacted. They should be informed of the target dry film thicknesses of the total system to be applied, not just the primer thickness, as the surface profile depth must be compatible with the entire coating system. It is advisable to receive written confirmation of their recommendation, rather than relying solely on verbal communication. Industry Standards for Assessing Surface Cleanliness The ISO, SSPC, and NACE surface cleanliness standards prescribe a minimum acceptable level of cleaning, depending upon the specified degree of cleanliness required. The standards are known as “consensus documents” that are created by industry experts for inclusion in coating specifications. They are not laws or regulations, but they become “contract law” once they are invoked in a specification for a coatings project. The seven ISO surface preparation standards are described in ISO Standard 8502. These standards define the level of cleaning required, and many of them are accompanied by visual guides that an inspector can use to verify that the minimum level of cleaning has been achieved. There are currently seventeen SSPC surface cleanliness standards. NACE and SSPC have jointly published ten of them; SSPC is the sole publisher of the remaining seven. The written standards for surface cleanliness are contained in Volume 2 of the SSPC Painting Manual, “Systems and Specifications” and are available for individual download from www.sspc.org. The surface cleanliness Protective Coatings Inspector Training ©2015 SSPC
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standards, their designations and definitions will be described later in this module, along with the proper use of the visual guides. SSPC Visual Guides and Reference Photographs In addition, there are currently four SSPC visual reference guides that have been developed for industry use. To select the correct visual guides and reference photographs, simply ask yourself, “What does the project specification require regarding the method of surface preparation?” Then select from one of the four visual guides and reference photographs currently available.
SSPC visual standards for surface preparation
• • • •
SSPC-VIS 1, “Guide and Reference Photographs for Steel Surfaces Prepared by Dry Abrasive Blast Cleaning,” SSPC-VIS 3, “Guide and Reference Photographs for Steel Surfaces Prepared by Power and Hand Tool Cleaning,” SSPC-VIS 4/NACE VIS 7, “Guide and Reference Photographs for Steel Surfaces Prepared by Waterjetting,” or SSPC-VIS 5/NACE VIS 9, “Guide and Reference Photographs for Steel Surfaces Prepared by Wet Abrasive Blast Cleaning.”
Note: SSPC-VIS 2 is not used for surface preparation. It is not included in this module. These visual guides and reference photographs are designed for use as guides. In the event of a dispute, it is the written surface cleanliness definitions that prevail. Also, the photographs in the guides will
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likely not provide an exact match to the surfaces prepared on your project, because the initial condition of the surface, the abrasive or tool employed, the surface profile, lighting and other factors can affect the appearance of the surface. Therefore the visual guides and reference photographs are truly designed as guides. In fact, many specifications now require the contractor to prepare a project-specific cleanliness standard on the actual structure to be cleaned and coated. The project-specific standard represents the actual initial condition, the actual abrasive or tool employed, the surface profile depth and other jobsite conditions. The SSPC visual guides and reference photographs can be used during this process to establish the minimum acceptable cleanliness level for the specific project. Once established, this area can be preserved until the surface preparation portion of the project is completed.
Pre-Surface Preparation Inspection Prior to beginning surface preparation operations, many specifications will be required to verify that fabrication defects (that may adversely affect coating system performance) are corrected, and that surface contamination (such as grease, oil, cutting compounds, lubricants and chemical contaminants) are sufficiently removed. Some common fabrication defects will be discussed next. It is important to realize however, that unless the governing specification requires these areas to be addressed, the contractor should not be required or expected to perform corrective action. Weld Spatter Weld spatter may be present on steel sections or pipe sections that were welded together using stick, flux core, gas metal arc (MIG) or gas tungsten arc (TIG) methods. Weld spatter is typically not present when submerged arc welding is performed. Welders are expected to remove weld spatter as it occurs. Spatters of weld rod material deposited on the steel surface from welding operations can result in spot corrosion if it is not removed from the surface prior to coating application. Weld spatter is a protrusion from the surface.
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While coating may be deposited onto the spatter, surface tension that is created between the protrusion and the coating causes the coating to draw thin on the spatter. The spatter may eventually remove itself from the steel, creating a void in the coating system and a pathway for corrosion of the underlying steel. For these reasons, many specifications will require the contractor to remove weld spatter (using chisels or grinding wheels) prior to surface preparation and coating system Weld Spatter installation. If required by the specification, the inspector must visually inspect the weld areas for spatter and identify areas where weld spatter remains.
Preparation of Welds in Tanks and Vessels for Immersion Service Appendix C of NACE Standard SP0178, “Standard Recommended Practice – Fabrication Details, Surface Finish Requirements, and Proper Design Considerations for Tanks and Vessels to be Lined for Immersion Service” contains written and graphic descriptions of five degrees of surface finishing of welds that can be specified prior to lining tanks or vessels for immersion service. The appendix is supplemented with a molded plastic weld replica comparator illustrating the weld condition prior to finishing and the various degrees of preparation for butt welds, fillet welded tee joints and lap welds. The degree of preparation (grinding) ranges from “minimal” (designation “E”) to smooth & blended (“D”), smooth and free of defects (“C”), smooth (“B”) and flush and smooth, free of all defects (“A”). Designations A & B are only applicable to butt welds. A coatings inspector may be responsible for verifying that the degree of weld grinding meets the requirements of the contract documents (specification) prior to surface preparation and lining installation. Condition of Edges/Corners “Sharp” edges and corners, such as those generated by torch cutting operations are difficult to coat, as the coating tends to pull away (draw thin) on the corners during application because of the surface tension that is created on the sharp edge. Some coatings have characteristically Protective Coatings Inspector Training ©2015 SSPC
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good “edge retention” properties, while others that shrink a lot during the drying and curing processes may have relatively poor edge retention properties. However, the inspector does not have to know how well or how poorly a coating will protect edges. The inspector is only responsible for verifying that edge preparation is performed and performed properly (according to the specification requirement) prior to surface preparation and coating installation.
Grinding Edges
Specification requirements for edge/corner preparation vary widely. Common examples include: 1.6 mm (1/16") radius or chamfer, 3.2 mm (1/8") radius or chamfer, and even “break all edges,” while some specifications do not address edge preparation at all. A tactile and/or visual assessment is typically all that is required, along with documentation that edge/corner preparation was satisfactory. Treatment and inspection of flame cut edges is particularly important. Flame cut or torch cut edges are typically very sharp, and the heat generated by the torch hardens the surface of the steel in these areas. Subsequent abrasive blast cleaning may not generate an adequate surface roughness on these edges, which can lead to coating adhesion problems, especially when a metallized coating is being applied. Oftentimes, these areas must be ground to remove the hardened Flame Cut Edges surface. The inspector should obtain surface profile measurements in these areas to ensure that the specified profile has been achieved.
Striping or Stripe Coat
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Some project specifications will require the application of a “stripe coat” to edges and corners (as well as other “difficult to coat” areas) to help ensure that these surfaces are adequately protected, even if edge preparation is specified. Striping will be discussed in more detail in Module 5. Briefly, striping is a single or multi-layer application of coating to edges, corners, bolt/nut assemblies, rivets, weld seams, bolt holes and other surfaces that are traditionally hard to protect from corrosion. The stripe coat can be brush or spray applied, however spray application to edges and corners is often 3-9
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preferred, as brushing can actually pull wet coating off of the edge, rather than deposit it onto the edge or corner. SSPC-PA Guide 11 Protecting Edges, Crevices, and Irregular Steel Surfaces by Stripe Coating discusses“striping” as a way of providing extra corrosion protection measures on edges, outside corners, crevices, bolt heads, welds, and other irregular steel surfaces, including optional surface preparation techniques for sharp edges to improve coating performance. Some details, including the advantages and limitations of specific methods of obtaining additional coating thickness, are described to assist the specification writer in assuring that the project specification will address adequate corrosion protection. Laminations Laminations occur during the rolling process in the steel mill. These laminations may be visible prior to blast cleaning, or may be raised during abrasive blast cleaning operations in the shop, creating a sliver that projects from the surface. These steel defects must be removed, typically by grinding; otherwise they may project above the coating film and subsequently corrode. The inspector should visually assess the prepared surfaces for slivers and laminations before and Lamination Sliver after abrasive blast cleaning. If discovered after blast cleaning, the affected area may have to be re-abrasive blast cleaned after grinding is completed. Substrate Replacement Older structures that have extensive corrosion may exhibit severe section loss, requiring replacement or patching of a portion of the structure. Examples include the “belly” of an elevated storage tank that has severe pitting (or even perforations), or structural steel beneath the roadway deck of a bridge structure that has been subjected to years of deicing materials. A structural engineer may ultimately determine that Protective Coatings Inspector Training ©2015 SSPC
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substrate replacement is required, which can involve removal of the effected areas by torch cutting and installation of replacement steel by welding, or simply welding a new section of steel over the deficient sections (patching). In any case, these operations must be performed prior to final surface preparation and coating system installation. If substrate replacement is required, the inspector must verify that all work is complete and is acceptable to the structural engineer prior to surface preparation operations. Subsequent rework of these areas after surface preparation will require rework by the painting contractor, which can adversely impact project cost and schedule. Removal of Grease, Oil, Cutting Compounds and/or Lubricants SSPC-SP 1, Solvent Cleaning SSPC-SP 1, “Solvent Cleaning” requires the removal of all visible grease, oil, lubricants, cutting compounds and other non-visible contaminants from the surface by cleaning with solvent, vapor, alkali, emulsion or steam (described earlier in this module). SP1 is a prerequisite to nearly all of the remaining twelve SSPC surface cleanliness standards, as mechanical methods of cleaning cannot remove this type of surface contaminant and may spread the contamination across the surface. Therefore, the inspector should recognize that solvent cleaning to remove surface contamination is an indirect requirement of the contract, even if the project specification is not explicit, as long as the specification references an SSPC or NACE surface cleanliness standard. There is no surface profile requirement for solvent cleaning. Grease, oil, cutting compounds or lubricants used in the steel fabrication process, or that have become deposited onto existing surfaces while in service can adversely affect the performance of the newly-installed coating system unless they are detected and adequately removed prior to surface preparation. In addition to potentially interfering with adhesion of the installed coating system and interfering with proper wetting of the substrate by the coating during application (causing a defect known as “fisheyes”), these contaminants can be driven into the surface during surface preparation and/or can contaminate the abrasive media used for surface preparation (power tool cleaning and abrasive blast cleaning). This is particularly problematic when the abrasive will be recycled and reused. If the Protective Coatings Inspector Training ©2015 SSPC
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abrasive becomes contaminated and is reused, it too can deposit the contamination onto cleaned surfaces. For these reasons, it is important that the surfaces be visually inspected for grease and oil contamination prior to surface preparation. If these contaminants are present, the contractor is responsible for properly removing them as most of the SSPC surface cleanliness standards invoke solvent cleaning (according to SSPC-SP1, discussed later in this module) if these types of contaminants (and any water-soluble contaminants) are visibly evident. Organic contaminants such as grease, oil, cutting compounds or lubricants can be removed using solvents such as methyl ethyl ketone (MEK), xylene, or proprietary cleaners sold by coating manufacturers. Other cleaning methods include steam (with or without a cleaning compound or detergent) or pressure washing with a cleaning compound or detergent capable of dissolving the contamination. Many solvents are toxic and care must be taken during handling. Petroleum solvents and turpentine are effective degreasers. Aromatic solvents are more effective, but are generally more toxic. The flash point of these solvents (the temperature at which there is sufficient vapor to ignite if a spark is generated) is relatively low and can pose a jobsite hazard. Safety precautions include proper ventilation, no smoking or open flames, proper equipment grounding and personal protective equipment. The solvents must also be disposed of properly. Chlorinated solvents (i.e., methylene chloride) are very effective degreasers; however they should not be used for general cleaning, as they are carcinogenic (cancer causing agents). Special training and proper personal protective equipment must be employed when using chlorinated solvents. These types of solvents should never be used to prepare stainless steel, as they can cause substrate deterioration. Water cleaning with detergent is much less toxic and can be effective in removing light deposits of grease and oil. Alkaline cleaners are also effective degreasers. The most common is trisodium phosphate (TSP), which can be added to hot tap water (15 grams per liter of water). It is common for a soapy film to remain on the surface when employing alkaline cleaners. It is important that the surfaces are thoroughly rinsed, then tested for residual alkalinity. Otherwise the coating may adversely react with the surface, resulting in a failure. Emulsion type cleaners often contain oil soluble soaps or emulsifying agents and Protective Coatings Inspector Training ©2015 SSPC
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are diluted with Kerosene or mineral spirits. They may be sprayed onto the surface, then rinsed by pressure washing. Similar to alkaline cleaners, a residue is often left on the surface, which must be removed prior to coating application. The residue can be removed by steam, hot water with detergent, solvents or alkaline cleaners. Steam cleaning employs steam, or a combination of steam and pressurized hot water. An alkaline cleaner can also be added to the hot water to help remove grease and oil. If an alkaline agent is added to the water, the surfaces must be thoroughly flushed with hot water, then tested for residual alkalinity. Inspection of these surfaces after cleaning is typically done visually or by wiping with a clean rag. Note that surface oil can be detected forensically in a laboratory using infrared spectroscopic analysis. However, it is not practical for an inspector to Inspection of Surface Using a Clean Rag sample a surface (typically by rinsing the surface with a laboratory solvent and collecting the rinsings) and forward the sample to a laboratory, as this can be costly and will result in project delays while waiting for the results of the analysis. Rather, detection of oil needs to be performed and the results known within a few minutes. This is why surface oil detection is typically a visual inspection. The visual inspection can be enhanced through the use of a black light, which will cause many “hydrocarbon” oils to fluoresce. (Note that some synthetic oils will not fluoresce under black light exposure, which may result in a false negative for the presence of contamination.) To detect surface oils using a black light, shine a short or long wavelength black light onto the surface. In daylight or conditions of sun, a black sheet or drape may be required to shield the area from atmospheric light. Note that lint on the cloth or small cloth fibers on the steel surfaces may fluoresce, but is not an indication of oil contamination. A bright yellow/green fluorescence of the surface indicates the presence of grease or oil contamination. Another way to detect oil or grease on a surface is by performing a water break test. In this case, atomize clean water onto the surface
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using a spray atomizer. Observe the reaction of the water on the surface. That is, if the water forms “lenses” that remain for 25 seconds or so before flowing together, the surface is free of oil. However, if the water forms into droplets (forms a “water break”) within the 25 seconds, it is likely that the surface contains grease, oil or another contaminant that is not soluble in water. Removing Stratified Rust, Pack Rust and Rust Scale Stratified rust, pack rust and rust scale occur when the iron oxides form in a defined shape, rather than in grains or powder. Pack rust often occurs between mating surfaces (crevices), whereas rust scale and stratified rust form on the surface of the steel. Stratified rust, pack rust and rust scale can be dislodged from the surface in pieces or layers. Some of the rust can adhere so tightly to the base metal that even a power wire brush will not remove it. Even though this may be considered “tightly adhering,” it is a very poor surface over which to apply coatings. The rust will eventually dislodge from the surface, taking the coating with it and leaving unprotected substrate. Oftentimes, stratified rust, pack rust and rust scale must be removed using hammers, impact tools such as pneumatic chipping hammers, scabblers, needle scalers or rotary impact flap tools. Many of these tools are described later in this module. Sampling, Detecting, and Removing Chemical Contamination Chemical contaminants on a surface can include chloride, ferrous ions, sulfates and nitrates, among others. These chemicals are deposited onto surfaces while the structure is in service, or during transportation of new steel to the fabrication shop. These chemicals are soluble in water, which is both good and bad news. The good news is that since the contaminants are water-soluble, they can typically be removed from surfaces by pressure washing or water jetting using clean water or water with the addition of a proprietary salt removal-enhancing solution. The effectiveness of the washing step is dependent on the condition of the surface. That is, contamination is relatively easy to remove from smooth surfaces, but may be more challenging if the surfaces are pitted or are configured with difficult-access areas, as contamination will tend to concentrate in these areas. The bad news is that if the salts are not detected or are not adequately dissolved and
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rinsed from the surfaces, they can become trapped beneath a newlyinstalled coating system. Provided that there is a sufficient quantity of water in the service environment, the water-soluble contaminant trapped beneath the coating system will draw the water through the coating film by a process known as “osmosis.” This drawing force can be quite powerful, and will continue until the concentration of salt in water is the same on both sides of the coating film (the concentration reaches equilibrium). This process creates a build-up of water and pressure beneath the coating film, oftentimes enough to cause blistering of the coating (known as osmotic blistering), underfilm corrosion and premature coating failure.
ISO 4628-2 and ASTM D714 describe blister assessment. Additionally, if soluble salts on the surface are not sufficiently removed prior to abrasive blast cleaning, recycled abrasive media can become contaminated, which can lead to contamination of surfaces that were not originally contaminated. It is for these reasons that many specifications are now requiring inspection of surfaces for chemical contaminants after surface preparation operations are complete, but before Sampling for chemical primer application. Because this type of contamination cannot contamination be detected visually, the surface must be sampled and the “surface extraction” tested for the contaminant(s) of concern. The International Standardization Organization (ISO) has developed testing methods for sampling and analysis of soluble salts. These methods are similar to those described in SSPC-Guide 15. The ISO standards for surface soluble salt detection are listed below. These methods (known as “Parts”) are housed in ISO 8502, “Preparation of Steel Substrates before Application of Paints and Related Products – Tests for the Assessment of Surface Cleanliness:” Part 5 Measurement of Chloride on Steel Surfaces prepared for Painting–Ion Detection Tube Method (ISO 8502-5) Part 6 Extraction of Soluble Contaminants for Analysis – The Bresle Method (ISO 8502-6) Part 9 Field Method for Conductometric Determination of Watersoluble Salts (ISO 8502-9) Part 10 Field Method for the Titrimetric Determination of Watersoluble Chloride (ISO 8502-10)
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The step-by-step instructions for extracting a sample from a surface and analyzing the collected sample for chloride, ferrous ion, conductivity and pH are described later in this module. A proprietary kit for testing the extracted sample for sulfates and nitrates is also described. SSPC-Guide 15, “Field Methods for Retrieval and Analysis of Soluble Salts on Substrates” describes methods for sampling and analysis of soluble salt contamination. Guide 15 is contained in Volume 2 of the SSPC Painting Manual, “Systems and Specifications,” and can be downloaded from www.sspc.org. In general, the methods of extracting soluble salts from surfaces include: 1. Surface swabbing 2. Latex patch/cell with injection syringe 3. Latex sleeve The methods of analysis of the extracted soluble salts include: 1. Chloride ion titration strips 2. Drop titration (chloride) 3. Chloride ion detection tubes 4. Ferrous ion strips 5. Nitrate ion strips 6. Conductivity meter (all soluble salts) 7. Turbidity meter (sulfate ion) Since there is no “industry standard” for tolerable levels of chemical contaminants, the project specification must indicate the maximum quantity of soluble salts that can remain on the surface and be safely coated over. For example, the specification of the coating of the interior of a water storage tank may specify a relatively low surface concentration of soluble salt, since the service environment is “immersion,” while the exterior of the same tank may not be as restrictive, since the service environment (the environment that the coating system must perform in) is not as aggressive.
Testing for Chemical Contamination If required by the specification, a final test is performed to determine whether surface chemical contamination (e.g., chloride, ferrous ions, sulfates and/or nitrates) has been reduced to tolerable levels. If the levels remain too high, then additional surface preparation may be required prior to application of the primer. Protective Coatings Inspector Training ©2015 SSPC
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How Do I Test for Soluble Salt Contamination? There are two widely accepted techniques for testing salt contamination. The technique that you select is based on whether you want to know both the quantity and the type of water-soluble salt that is on the surface or whether you just want to know if watersoluble salts are present. The first technique is known as “specific ion detection;” the second technique is called “conductivity.” What is Specific Ion Detection? Specific ion detection will tell you whether a specific type of watersoluble salt is on the surface (for example, chlorides, sulfates, ferrous ions, etc.) and how much of each one is there (as long as you test for them). If you select this testing technique you will need to sample the surface, then test the sample for each of the water-soluble salts that you are concerned may be on the surface. What is Conductivity? Water-soluble salts will increase the electrical conductivity of pure water. For example, salt water will conduct electricity a lot better than distilled water. Therefore, if you sample the surface with pure water and test the water sample, an increase in electrical conductivity indicates that the water has extracted salts from the surface. However, conductivity testing will not be able to tell you what type of salt is on the surface, only that there is some type of water-soluble salt that is causing the electrical conductivity of the water to increase. Some individuals will assume that an increase in conductivity is an indication that chloride is on the surface, and they will “convert” the conductivity to a chloride concentration. These individuals are assuming a worst-case scenario (i.e., being conservative), since chloride is considered the most detrimental of all water-soluble salt contamination.
How Do I Test for Specific Ions and Conductivity? There are a variety of methods that can be used to sample the surface, and there are several methods that can be used to test the collected sample. Unless the project specification tells you what test method to use, the first step is to select one. SSPC Technology Guide 15, “Field Protective Coatings Inspector Training ©2015 SSPC
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Methods for Retrieval and Analysis of Soluble Salts on Steel and Other Non-Porous Substrates” describes the most commonly used extraction and testing methods. You will be learning about several of them. But first, you will need to decide if you want to test for specific ions or test for conductivity. Select a technique for testing the surface for water-soluble salt contamination: Technique for Testing Salt Contamination
Select One (ü)
Specific Ion Detection Conductivity
Selecting a Field Sampling and Testing Method If you select “specific ion detection” there are several field sampling techniques and several field testing methods to choose from. The ones we will focus on in this Module will tell us whether chlorides, sulfates and ferrous ions are present and how much of each is there. If you select “conductivity” there are several field sampling techniques to choose from, but only one field testing method that can be used. To select a test method first ask yourself, “What does the project specification require?” If the specification does not require a specific method, then you can select from any of the methods available. This module describes several Surface Contamination Analysis Test (SCAT) kits. The sampling and testing methods, and the possible combinations of SCAT kits are shown in the charts on the next page. Chart 1 lists three methods of collecting a sample from the surface, and Chart 2 contains five methods for testing the collected sample. Unfortunately, not all of the sample collection methods and sample testing methods are compatible. Chart 3 lists the possible combinations of sampling and testing methods. SCAT kits are available in any of the combinations shown in Chart 3.
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Section 1 describes the step-by-step procedures for each of the three sample collection procedures (A-C) listed in Chart 1, while Section 2 describes the step-by-step procedures for each of the five sample testing procedures (1-5) listed in Chart 2. Chart 2
Chart 1
Methods of Sample Testing
Methods of Sample Collection A. Surface Swabbing
1. Quantab® Chloride Titrator Strip
B. Latex Sleeve (Chlor-Test® Kit)
2. Kitagawa® Chloride Titrator Tube
C. Latex Cell (Bresle Patch™ and BresleSampler®)
3. Bresle® Kit Drop Titration for Chloride 4. EM Quant® Iron Strip (ferrous ion) 5. Conductivity 6. Turbidity (sulfate)
Chart 3 – Combination of Sample Collection and Testing Methods Method of Sample Collection (from chart 1)
Method of Sample Testing (from Chart 2)
A. Surface Swabbing
1. 2. 4. 5.
Quantab® Chloride Titrator Strip Kitagawa® Chloride Titrator Tube EM Quant® Iron Strip (ferrous ion) Conductivity
B. Latex Sleeve (Chlor-Test® Kit)
2. 4. 5. 6.
Kitagawa® Chloride Titrator Tube EM Quant® Iron Strip (ferrous ion) Conductivity Turbidity (sulfate)
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Methods of Sample Collection Before you test a sample for soluble salt contamination, you will need to collect a sample or set of samples from the surface. There are three methods of collecting samples from a surface for testing. The step-bystep instructions are found in the supplement to this module.
___________________________________________ Surface Sampling Method A: Surface Swabbing Swab SCAT (Surface Contamination Analysis Test) Kit
Swab SCAT kit
The surface swabbing technique was one of the first sample collection methods available. The amount of soluble salt contamination actually sampled using the surface swabbing technique (better known as extraction efficiency) is relatively low, compared to some of the other methods we will be discussing. Despite its limitations, surface swabbing is still a viable technique for sample collection. The KTASwab SCAT kit contains all of the necessary equipment you will need to collect a sample from the surface, then test the sample for chloride, ferrous ion and pH.
Surface Sampling Method B: Latex Sleeve (Chlor*TestTM SCAT Kit)
Chlor* TesttmSCAT kit
The Chlor*TestTM SCAT Kit contains five latex sleeves and five bottles of Chlor*ExtractTM solution that are used for collecting a sample from the surface. The extraction efficiency of this method is better than the swabbing method.
Surface Sampling Method C: Latex Cell (Bresle PatchTM and BresleSampler®)
Bresle Patchtm, Bresle Sampler ®, and Extraction Syringe
There are two latex cells that can be used to collect a sample from the surface. They are both named “Bresle.” The Bresle PatchTM is an adhesive latex cell. The sampling area of the latex cell is 12.25cm2 and is square in shape. The BresleSampler® is also an adhesive latex cell. The sampling area of this latex cell is 12.5cm2 and is round in shape. Since the procedure for collecting a sample from the surface using these two latex cells is essentially the same, only the Bresle Patch™ is illustrated in the supplement.
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Methods of Sample Testing Now that you have collected a set of samples using one or more of the sample collection methods described in Section 1, you are ready to test the collected sample(s) for chlorides, ferrous ion, and/or conductivity. There are five methods for testing the collected samples for soluble salt contamination: (1) Quantab chloride titrator strips; (2) Kitagawa Chloride Titrator Tube; (3) Bresle SCAT Kit (Drop Titration for Chloride); EM Quant Iron Strip (Ferrous Ion); 5. Conductivity. The step-by-step instructions on how to perform the five methods for testing are described in the supplement at the end of this module. To determine conductivity, the inspector may be required to convert the value to surface concentration as described here. Converting Between Surface Conductivity and Surface Concentration You can estimate the surface concentration from the conductivity value you obtained using Sample Test Method 5 if the identity of the soluble salt is known or assumed to be sodium chloride. For example if it is known or assumed that the salt causing the increase in conductivity is sodium chloride only, the surface concentration can be estimated using the following formula (solving for “E”): E = 0.5 x S x V/A E = surface concentration of chloride in micrograms/square centimeter (µg/cm2) S = conductivity in microsiemen per centimeter (µS/cm) from Sample Testing Method 5 V = volume of water used to collect a sample from the surface, in milliliters (mL) A = area of sample collection, in square centimeters (cm2) Example: S = 70 µS/cm V = 2 mL (volume of water used in Latex Cell) A = 12.25 cm2 (area of Latex Cell) E = 0.5 x 70 x 2/12.25 = 5.7 µg/cm2 of chloride
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Note: This formula only works when it is known (or assumed) that sodium chloride is the only soluble salt in the test solution and when it is present at low concentrations. You can use a similar formula to convert surface concentrations to conductivity. In this case, you are solving for “S” rather than “E.” The same assumptions apply when using this formula. S = 2 x E x A/V Example: S = Conductivity in µS/cm E = 3.4 µg/cm2 of chloride A = 12.25 cm2 (area of Latex Cell) V = 2 mL (volume of water used in Latex Cell) S = 2 x 3.4 x 12.25/2 = 41.65 µS/cm (~70) Analyzing Surface Extractions for the Sulfate Ion Unlike chloride, ferrous ion and nitrate (which can be analyzed simply using test strips or indicator tubes), the analysis of sulfate is more complex and requires the use of an instrument known as a turbidity meter. Once the sample is collected from the surface (a minimum of 7 mL of solution is required), it is filtered through a Whatman Autovial, placed in a clear glass vial, inserted into the meter and the meter is “zeroed.” The clear glass vial containing the test solution is removed from the meter and a pre-measured amount (0.1 gram) of Barium Chloride is added to the test solution. The solution containing the Barium Chloride is vigorously shaken for 2 minutes, the glass vial is wiped to remove fingerprints and the vial is again placed in the meter and the “Read” button is depressed. The relative “cloudiness” or turbidity of the solution is converted to a sulfate concentration in parts per million (by the meter). By knowing the amount of solution used for the extraction (in milliliters) and the area sampled (in square centimeters), the concentration of sulfate per unit area (micrograms per square centimeter) can be calculated. The methods employed to collect a sample for sulfate measurements (swabbing, latex patches/cells, latex sleeves) have already been described. Remember that if an extraction method other than the latex sleeve is employed, a minimum of 7 mL of solution is required for Protective Coatings Inspector Training ©2015 SSPC
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the test. If the area extracted and the amount of extraction solution used are not the same values (e.g., 10), then the PPM reading from the meter must be multiplied by the amount of solution used for the extraction (in mL), then divided by the area extracted (in cm2) to arrive at μg/cm2. Measuring Ambient Conditions Prior to Final Surface Preparation The measurement of air temperature, relative humidity, dew point temperature and surface temperature is usually associated with coating application. However, if the air temperature and relative humidity are such that moisture from the air condenses on the surface during final surface preparation, the surface may flash rust. Therefore, it is recommended to verify that the temperature of the surfaces is at least 3°C (5°F) higher than the temperature of the dew point, to preclude airborne moisture from condensing on the surfaces. These values (surface temperature and dew point temperature) can be obtained using sling or battery-powered psychrometers in conjunction with US Weather Bureau Psychrometric Tables and surface temperature thermometers, or can be obtained using direct read-out electronic psychrometers equipped with surface temperature probes. The step-by-step use of this instrumentation is described in the supplement at the end of this module. It is important that the inspector not rely on prevailing weather conditions from a local service (e.g., airport weather station) as conditions at the project site and the specific work area can vary considerably. Ambient conditions should be measured and recorded prior to initiating final surface preparation and at 4-hour intervals thereafter, unless conditions appear to be declining. In this case, more frequent checks may be required. If surface preparation work will be done inside a facility, tank or inside of a containment, then the prevailing ambient conditions inside of the areas (at the actual location of the work) should be assessed. The location, date, time of day and the conditions of air temperature, relative humidity, dew point temperature and surface temperature should be recorded. However, since the only operation being monitored is surface preparation, the dew point – surface temperature relationship is the most critical. Typically there is no specified range for air temperature and relative humidity during surface preparation operations.
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There are many instruments used to measure ambient conditions, and the industry continues to develop newer versions that will allow us to gather information faster and easier. We will focus on the instruments that are most commonly used at the time of this writing. This module details the use and calibration of the following instruments and charts:
Sling psychrometer Battery-powered psychrometer Electronic psychrometers US Weather Bureau Psychrometric Tables Dial surface temperature thermometers Digital surface temperature thermometers and non-contact infrared thermometers
Using Psychrometers to Measure Ambient Conditions
Sling Psychrometer and the US Weather Bureau Psychrometric Tables
The most common (and most economical) method of measuring the ambient conditions on a project site is by using either a sling or battery-powered psychrometer, in conjunction with the US Weather Bureau Psychrometric Tables. The psychrometer is used to measure the air temperature and to assess the latent heat loss caused by water evaporation from a wetted sock on the end of a bulb thermometer. The psychrometric tables are used to look-up the relative humidity and dew point temperature (based upon temperature readings from the psychrometer and the barometric pressure). For now, it is more important that we know how to obtain the information. We will discuss what the information means later in the module.
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Using Electronic Psychrometers to Assess Ambient Conditions An alternative to sling and battery-powered psychrometers are the electronic psychrometers. There are several models on the market. However, some of these psychrometers are affected by outdoor conditions and are not recommended for exterior use. It is important to inquire about outdoor use prior to purchasing one of these electronic psychrometers. Any of these psychrometers can be used for shop painting, provided the work is done in an enclosed facility.
PosiTector® Dew Point Meter
Elcometer 319
Extech RH 401
The most common and versatile electronic psychrometers consist of a wand or probe that is exposed to the environment (and touched to/ pointed at the surface). A digital display indicates a dataset, including the air temperature, the relative humidity, the dew point temperature, the surface temperature and the numerical spread between the surface temperature and the dew point temperature. Since the electronic psychrometers automatically measure and display the ambient conditions and surface temperature, their use is fairly straightforward. Basic step-by-step instructions are provided in the supplement at the end of this module. The instruction manuals provided with the gages should be consulted to understand their full capabilities.
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Using Surface Temperature Measuring Instruments There are a variety of instruments for measurement of surface temperature, including dial type and digital contact thermometers as well as non-contact infrared thermometers. As discussed earlier, some electronic psychrometers also have surface temperature measurement capability. Dial type surface temperature thermometers contain a bi-metallic, temperature-sensing spring on the back of the thermometer that expands and contracts with the temperature of the surface. Since the spring is attached to the indicator needle on the front side of the thermometer, the needle increases and decreases on the temperature scale, indicating the surface temperature. Dial type surface temperature thermometer Magnets attached to the back of the (left is backside; right is frontside thermometer enable self-attachment to vertical steel surfaces, although this thermometer can be used on almost any surface.
Temperature-sensing spring
Thermocouple digital surface temperature gages are quicker and more accurate than the dial type, but are typically more expensive. Thermocouple digital
Non-contact IR thermometer
Non-contact infrared thermometers can also be surface thermometer used to measure surface temperature. These gages are often equipped with laser sightings, so that you can target the location on the surface to be measured. However, the further away from the surface that the “gun” is held, the larger the area of measurement is, causing potential error. Also, there is a maximum distance, depending on the make and model of the thermometer. You should carefully read the manufacturer’s instructions prior to use. Measuring surface temperatures with infrared lasers can produce erroneous temperatures when the steel is roughened or abrasive blast cleaned.
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Calibrating Instruments for Measuring Ambient Conditions and Surface Temperature Verifying the accuracy of any coating inspection instrument is paramount to the reliability of the data it produces. This section describes the verification procedures for instruments used to assess ambient conditions and surface temperature. Verification of Accuracy – Psychrometers The bulb thermometers in sling and battery-powered psychrometers cannot be “calibrated” per se. However, their accuracy should be routinely verified. Verification of Accuracy – Dial Type Surface Temperature Gages Dial type surface temperature gages also cannot be calibrated, but they should be verified for accuracy routinely. A calibration curve can be generated by comparing the readings to a certified thermometer. Calibrating Digital Psychrometers, Digital Surface Temperature Thermometers and Non-contact Infrared Thermometers Digital psychrometers, digital surface temperature thermometers and the non-contact thermometers can be calibrated by the manufacturer, and their accuracy can sometimes be verified by the operator. Always follow the manufacturer’s recommendations for calibration verification method(s) and frequency, as the specific method varies depending on the manufacturer and model of the instrument.
Documenting Ambient Conditions and Surface Temperature Independent of the instrumentation used to assess the prevailing ambient conditions and surface temperature, it is important to document the measurements, including the date and time of day that the measurements were obtained. The location where the readings were obtained is also important; and some projects will require documentation on the instrument type and serial numbers of the gages. Protective Coatings Inspector Training ©2015 SSPC
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The table illustrates a typical data set for ambient conditions and surface temperature. Condition Date Time Dry Bulb Temperature (t) Wet Bulb Temperature (t') Depression (t-t') Relative Humidity Dew Point Temperature Surface Temperature Measurement Location
Data 5/13/02 1300 16°C (60°F) 13°C (55°F) 3°C (5°F) 73% 11°C (51°F) 15°C (59°F) West side of tank, ground level
Dehumidification In some cases, the ambient conditions and surface temperature on a project site are such that work should not proceed, as there is a chance that moisture may condense on a surface during final surface preparation. In most instances, final surface preparation work is postponed until conditions improve. While this approach is quite common, it can adversely impact the project schedule. If the area in which surface preparation is taking place is contained, the contractor or facility owner may elect to control the environment using dehumidification (DH) equipment, so that work can proceed. This type of equipment effectively removes moisture from the air, thereby reducing the chance of condensing moisture on a surface. While dehumidification seems like a straightforward process, the equipment must be appropriately sized to dehumidify the area, and must be properly set-up and maintained. Mobilization and operation of DH equipment can also escalate project costs. Therefore, the inspector should not require the use of DH equipment unless stipulated by the project specification. The contractor may elect to mobilize the equipment on his own, in order to maintain the project schedule. Ultimately, the inspector verifies that the ambient conditions and surface temperatures conform to the project specification. The means and methods of achieving these conditions are up to the contractor. It is beyond the scope of this training to provide comprehensive instruction on the set-up and operation of DH equipment. However, it is important that an inspector have a background in DH principles Protective Coatings Inspector Training ©2015 SSPC
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and equipment. For more detailed information on dehumidification, the inspector should read SSPC Technical Report TR 3/NACE 6A192, “Dehumidification and Temperature Control During Surface Preparation, Application, and Curing for Coatings/Linings of Steel Tanks, Vessels, and Other Enclosed Spaces.” The information provided below was extracted from the report. Dehumidification can be accomplished by compression, refrigeration, desiccation (liquid sorption, solid sorption), or a combination of these systems. While compression and liquid sorption are common methods of dehumidification, their use is not generally applicable to field conditions. Therefore, only the refrigerant-based and desiccant solidsorption techniques are described. Refrigeration The cooling of air to below its dew point is an economical method of dehumidification. This method is commonly used at ambient temperatures of approximately 29°C (85°F) and high humidity. Ambient air is circulated over a system of refrigeration coils. The surface temperature of the coils is set at temperatures considerably lower than the temperature of the incoming ambient air. As the air cools, it reaches saturation, and condensation forms. This condensation is collected and removed from the system. The air exits the cooling-coil section of the dehumidifier at a reduced temperature, dew point, and absolute humidity. The refrigeration-based dehumidification system is illustrated in Figure 1. The cooler air, which has a lower dew point, can then be reheated to lower the relative humidity.
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Refrigeration is often used to pre-cool and dehumidify inbound air before it reaches a desiccant system in order to obtain lower dew points after desiccation. The air can be re-cooled, if necessary, by refrigeration. Desiccant Solid-sorption dehumidification systems utilize either granular beds or fixed desiccant structures. These structures are contained within machines through which an air stream is passed. The desiccant used is in an active, dehydrated state and has a vapor pressure below that of the air to be dehumidified. The most commonly used desiccants are silica gel and lithium chloride. Air is passed through beds or layers of the desiccant, which absorb moisture from the air stream, producing a hydrated salt. Regeneration of the hydrated salt is accomplished with heated air, which drives off the water of hydration, returning the sorbent to its dehydrated state. The previously sorbed moisture is diverted to a separate air stream.
The exothermic hydration reaction typically raises the temperature of the exiting air stream by 6 to 8°C (10 to 15°F). Therefore, in hot climates, refrigeration-type dehumidifiers are frequently used in combination with desiccant equipment to cool the air entering the space. A typical desiccant dehumidification system is illustrated in Figure 2. Because this type of system absorbs moisture as vapor, it is commonly used at all temperatures and levels of humidity. Protective Coatings Inspector Training ©2015 SSPC
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Sizing Equipment The size of dehumidification equipment is typically determined by considering the balance between air extraction from the space and the dehumidification desired to accomplish the specified dew point depression from the surface temperature. If the capacity of the dehumidification equipment becomes marginal through unexpected weather changes, its efficiency can be improved by reducing the amount of air being extracted for dust control. The appropriate air-change rate for maintaining a prepared surface during blast cleaning and between shifts while maintaining a large differential between dew point and surface temperature for an extended period of time is dependent on air-space volume, equipment, geographical location, climate, and season. The number of openings in the enclosure, the airtightness of the structure, the distance of equipment from the space, and the amount of air to be extracted or exhausted by means other than DH equipment also influence the DH capacity. Relatively airtight enclosures generally require less DH volume because little or no additional air or moisture is introduced into the space. Relatively large spaces usually require fewer air exchanges. Equipment contractors usually have guides that give volume data for their equipment. Assessing Lighting and Surface Cleanliness There is one key element to inspection on every project: Adequate lighting. You can’t inspect what you can’t see. If you can’t see, you can’t inspect! Lighting is particularly critical when assessing surface cleanliness, as it is a visual inspection check point. Therefore, before describing the ISO and SSPC/NACE visual guides for surface cleanliness and the inspection procedures employed to assess surface cleanliness, it is important to understand how light is measured and what is considered “adequate.” SSPC Guide 12, “Guide for Illumination of Industrial Painting Projects” describes the minimum and recommended lighting requirements for various operations on a painting project. These are listed below in the chart. In addition, the instrumentation used to assess the adequacy of the lighting is also described in the Guide. The term “Foot Candle” indicates the amount of light emitted by a candle 12 inches away (and perpendicular to) from the light source; the term Protective Coatings Inspector Training ©2015 SSPC
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“Lux” or “Meter Candle” indicates the amount of light emitted by a candle 1 meter away (and perpendicular to) from the light source. A standard light meter is used to assess the prevailing amount of lighting in an area. There are several models available and their use is straightforward. Simply power-up the light meter and select the output units (Lux or Foot Candle). The instrument display will indicate the amount of light reaching the photocell. Compare the readout on the display to the requirements of the project specification (or SSPC Guide 12) for the type of operation being performed. You should obtain at least five measurements to ensure that the lighting is uniform across the entire area. SSPC Guide 12 Lighting Requirements Operation General Area Surface Preparation Coating Application Inspection
Lighting (Lux or Meter Cande) Minimum Recommended 108 215 215 538 215 538 538 2153
Lighting (Foot Candle) Minimum Recommended 10 20 20 50 20 50 50 200
Even with adequate lighting, determining visually whether the degree of cleanliness achieved by the contractor meets/exceeds the minimum level required by the project specification is perhaps the most difficult inspection check point. That is, there is no instrument that can be placed onto the surface to indicate the level of surface cleanliness attained. The instrument used is the inspector’s eyes. To assist in the visual assessment of surface cleanliness, SSPC: The Society for Protective Coatings has developed four sets of reference photographs (known as “Visual Guides and Reference Photographs”). Each visual guide contains several “before” and “after” photographs. These visual guides and reference photographs can help you assess whether surfaces have been prepared according to the project specification before painting begins. The visual guides and reference photographs we will be learning about in this module use the same surface preparation designations as the written specifications.
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Power switch and read-out selector Light meter
Light meter in use
Methods of Surface Preparation Surface preparation methods employed by a painting contractor or facility owner can range from simple solvent cleaning to hand and power tool cleaning, dry and wet abrasive blast cleaning, chemical stripping, water jetting and other more non-traditional methods such as sponge jetting and cryogenic blast cleaning using dry ice pellets. As we discussed earlier in this module, the degree of cleaning required by a given project specification is dependent on the service environment (the environment that the coating system must perform in), the coating system and the intended service life of the coating once installed. Hand Tool Cleaning Hand tool cleaning is typically performed with wire brushes, scrapers and other tools that do not depend on electric or pneumatic power to operate. These hand tools are only intended to remove loosely adhering corrosion products, old paint and flaking mill scale, and are not intended to produce an anchor pattern in the steel. Hand tools are frequently used to prepare surfaces for spot touch-up during maintenance painting activities. Hand Tool
Since hand tool cleaning operations may leave unlimited amounts of intact coating, it is important that the edges of the intact coating be tapered or “feathered” to provide a smooth transition of the newly applied coating. Unfeathered edges can result in lifting of the Protective Coatings Inspector Training ©2015 SSPC
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coating at those edges, in addition to a poor appearance of the finished project. Feathering of edges can be accomplished using abrasive paper (sand paper) or various power tool attachments. Power Tool Cleaning Power tool cleaning is typically performed with grinders, pneumatic chisels, needle scalers, rotopeen tools and other tools that require an electric or pneumatic power source to operate. Most of these tools can remove both loosely and tightly adhering corrosion products, paint and mill scale from the steel surfaces. Stratified rust, pack rust and rust scale (described earlier in this module) are removed using these types of tools. Some of these tools can also produce an anchor pattern into the steel by “peening” the surface. Additionally, these tools can be purchased with vacuum ports and hoses for attachment to HEPA (High Efficiency Particulate Air) filtered vacuums so that the fine, airborne particles that are generated during surface preparation activities are collected at the point of generation. Similar to hand tool cleaning, power tool cleaning operations may leave unlimited amounts of intact coating. Therefore it is important that the edges of the intact coating be tapered or “feathered” to provide a smooth transition of the newly applied coating. As described earlier in this module, unfeathered edges can result in lifting of the coating at those edges, in addition to a poor appearance of the finished project. Feathering of edges can be accomplished using sanders, right angle grinders equipped with non-woven fiber wheels containing abrasive particles, or other less aggressive power tool attachments. Power Tool Cleaning – General The three power tool cleaning specifications all require the removal of visible grease, oil and other contaminants from the surfaces (as specified in SSPC-SP1 “Solvent Cleaning”) prior to initiating power tool cleaning. That is, SSPC-SP1 is an “indirect requirement” of SSPC-SP3 “Power Tool Cleaning,” SSPC-SP11, Power Tool Cleaning to Bare Metal,” and SSPC-SP15, “Commercial Grade Power Tool Cleaning.” When welded surfaces are encountered, the weld slag,
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flux and fume deposits should be removed to the extent possible (and as required by the contract documents), as coatings may not perform on welded areas containing these types of deposits. After cleaning and prior to painting, residual dirt, dust and other debris generated by the power tool cleaning operations should be removed by blow down using compressed air, or by brushing or vacuuming. If compressed air is used to remove surface debris, it must be both clean and dry, which can be verified by performing a compressed air cleanliness test (blotter test) described later in this module. Compressed air cleanliness is an “indirect” requirement of SSPC-SP3, SSPC-SP11 and SSPC-SP15. Selection of the power tool and cleaning media is dependent on many factors, including the amount of surface area to be cleaned, the configuration of the surface, and the level of control required for worker and environmental protection. Selection is also dependent on whether surface roughness is a direct requirement of the referenced SSPC surface cleanliness standard (e.g., SSPC-SP11 and SP15), or if a surface roughness is required by the contract documents. Needle scalers can both clean and roughen, and are useful for cleaning areas in tight configuration, but are too slow for cleaning large areas. Nonwoven fiber wheels clean well, but tend to polish the surfaces, leaving little to no surface profile. Rotary impact-type power tools both clean and roughen, and are more productive than needle scalers. Most power tools can be vacuum shrouded to reduce the volume of airborne dust generated by the cleaning process. The vacuum units are often equipped with High Efficiency Particulate Air (HEPA) filtration. Note however, that environmental protection is often still required, as the larger particles and debris dislodged from the surfaces are not always collected by the vacuum system, especially when uneven surfaces or protrusions are encountered. Determining whether the remaining rust, paint or mill scale is intact on surfaces prepared to SSPC-SP3 cannot be evaluated visually. Rather, a “dull putty knife” is used as the inspection tool to assess whether the remaining materials can be lifted. Even so, this evaluation can be subjective, and the term “dull” is relative and currently not welldefined. Determining the maximum amount of staining present after cleaning according to SSPC-SP15 is evaluated visually; however the process is no less subjective. And both SSPC-SP11 and SP15 allow trace Protective Coatings Inspector Training ©2015 SSPC
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amounts of rust, paint or mill scale to remain in the pits, provided the original surfaces were pitted. Establishing a project-specific cleanliness standard may help to better define the level of cleanliness required on a given structure. The area should be representative of the structure, and should be preserved as a reference in the event of a dispute later during the cleaning operations. Many contracts require the establishment of a project-specific cleanliness test area. This is described in more detail later in this module. When mutually agreed upon or when invoked by the contract documents, ISO 8501-1 or SSPC VIS 3 photographic references can be used to help evaluate the cleanliness of surfaces prepared by power tool cleaning. While the photographic references in ISO 8501-1 or SSPC VIS 3 will rarely match the actual surfaces prepared by the contractor, they serve as an excellent tool to help those evaluating the degree of cleanliness achieved to “calibrate” their eyes, and they are invaluable for establishing a jobsite cleanliness standard. The use of these visual guides is described later in this module. ISO Standard 8502, “Preparation of Steel Substrates before Application of Paints and Related Products – Tests for the Assessment of Surface Cleanliness.” The International Standards Organization has published written surface cleanliness standards for preparation of steel surfaces. These standards are housed in ISO Standard 8502, “Preparation of Steel Substrates before Application of Paints and Related Products – Tests for the Assessment of Surface Cleanliness.” The identification system and the definitions vary considerably from that of SSPC and NACE. Therefore these standards are described separately in this training. ISO St 2: Thorough Hand and Power Tool Cleaning “When viewed without magnification, the surface shall be free from visible oil, grease and dirt, and from poorly adhering mill scale, rust, paint coatings and foreign matter.” ISO St 3: Very Thorough Hand and Power Tool Cleaning “(Same) As for St2, but the surface shall be treated much more thoroughly to give a metallic sheen arising from the metallic substrate.” Protective Coatings Inspector Training ©2015 SSPC
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SSPC-SP 2, Hand Tool Cleaning SSPC-SP 2, “Hand Tool Cleaning” requires the removal of all loosely adhering rust, mill scale and paint. The remaining materials are considered tightly-adhering if they cannot be lifted using the blade of a dull putty knife. The project specification may require the edges of intact paint to be feathered to facilitate a smooth transition, and to prevent lifting of the edge by the application of subsequent coating layers. There is no surface profile requirement for hand tool cleaning. The hand tool cleaning specification requires the removal of all visible grease, oil and other contaminants from the surfaces (as specified in SSPC-SP 1 “Solvent Cleaning”) prior to initiating hand tool cleaning. That is, SSPC-SP 1 is an “indirect requirement” of SSPC-SP 2 “Hand Tool Cleaning.” When welded surfaces are encountered, the weld slag, flux and fume deposits should be removed to the extent possible (and as required by the contract documents), as coatings may not perform on welded areas containing these types of deposits. After cleaning and prior to painting, residual dirt, dust and other debris generated by the hand tool cleaning operations should be removed by blow down using compressed air, or by brushing or vacuuming. If compressed air is used to remove surface debris, it must be both clean and dry, which can be verified by performing a compressed air cleanliness test (blotter test) described later in this module. Compressed air cleanliness is also an “indirect” requirement of SSPC-SP 2. Determining whether the remaining rust, paint or mill scale is intact cannot be evaluated visually. Rather, a “dull putty knife” is used as the inspection tool to assess whether the remaining materials can be lifted. Even so, this evaluation can be subjective, and the term “dull” is relative and currently not well-defined. Establishing a project-specific cleanliness standard may help to better define the level of cleanliness required on a given structure. The area should be representative of the structure, and should be preserved as a reference in the event of a dispute later during the cleaning operations. Many contracts require the establishment of a project-specific cleanliness test area. This is described in more detail later in this module. When mutually agreed upon or when invoked by the contract documents, ISO 8501-1 or SSPC VIS 3 photographic references can be used to help evaluate the cleanliness of surfaces prepared by hand tool cleaning. While the photographic references in ISO 8501-1 or SSPC VIS 3 or in will rarely match the actual surfaces prepared by the Protective Coatings Inspector Training ©2015 SSPC
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contractor, they serve as an excellent tool to help those evaluating the degree of cleanliness achieved to “calibrate” their eyes, and they are invaluable when establishing a jobsite cleanliness standard. The use of these visual guides is described later in this module. Power Tool Cleaning SSPC has published three power tool cleaning standards. They vary in the level of surface cleanliness required and surface roughness requirements. SSPC-SP 3, Power Tool Cleaning SSPC-SP 3, “Power Tool Cleaning” is similar to SSPC-SP 2, “Hand Tool Cleaning” in that the standard requires the removal of all loosely adhering rust, mill scale and paint. The remaining materials are considered tightly-adhering if they cannot be lifted using the blade of a dull putty knife. The project specification may require that the edges of intact paint to be feathered to facilitate a smooth transition, and to prevent lifting of the edge by the application of subsequent coating layers. There is no surface profile requirement for power tool cleaning. SSPC-SP 11, Power Tool Cleaning to Bare Metal SSPC-SP 11, Power Tool Cleaning to Bare Metal” requires the removal of all loosely and all tightly adhering mill scale, rust and paint to expose the bare metal surface. If the existing surfaces are pitted, trace quantities of paint, rust and mill scale can remain in the bottom of the pits. The standard also requires that a minimum 25 µm (1 mil) anchor pattern or profile be etched into the bare steel surface, in order to enhance the mechanical bond of the newly-applied coating system to the prepared surfaces. Surfaces prepared according to SSPC-SP 11 are not to be compared to surfaces prepared by abrasive blast cleaning. While this level of cleaning may generate surfaces that resemble a near white or commercial blast (described later in this module), they are not equivalent to those surfaces due to the characteristics of the surface roughness (profile).
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SSPC-SP 15, Commercial Grade Power Tool Cleaning Similar to SSPC-SP 11, SSPC-SP 15, “Commercial Grade Power Tool Cleaning requires the removal of all loosely and all tightly adhering mill scale, rust and paint from the surface. Staining from rust, paint and mill scale is permitted, provided it does not exceed 33% (onethird) of each 58 cm2 (9 square inches) of prepared surface. If the existing surfaces are pitted, trace quantities of paint, rust and mill scale can remain in the bottom of the pits. SP 15 also requires that a minimum 25 µm (1 mil) anchor pattern or profile be etched into the surface, in order to enhance the mechanical bond of the newly applied coating system to the prepared surfaces.
Selecting a Visual Standard ISO 8501 is used for visual assessment of surface cleanliness. Similar to the SSPC Visual Guides and Reference Photographs, it contains color photographs of four rust grades of steel: A: “Steel surface largely covered with adhering mill scale but little, if any, rust.” B: “Steel surface which has begun to rust and from which the mill scale has begun to flake.” C: “Steel surface on which the mill scale has rusted away or from which it can be scraped, but with slight pitting visible under normal vision.” D: “Steel surface on which the mill scale has rusted away and on which general pitting is visible under normal vision.” Each of the four levels of abrasive blast cleaning (Sa 1, Sa 2, Sa 2 ½ and Sa 3) is depicted for each of the four rust grades. In addition the two hand & power tool cleaning levels are depicted for Rust Grades B, C and D, and flame cleaning is illustrated for each of the four Rust Grades. Three examples illustrating the proper use of the ISO surface cleanliness standards are provided below. Example 1: The surface contains no mill scale and is completely rusted. No pitting is visible. Protective Coatings Inspector Training ©2015 SSPC
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Rust Grade C The project specification requires “Very Thorough Blast Cleaning.” Sa 2 ½ The inspector uses the photographic standard labeled “C Sa 2 ½” to inspect the surfaces to assess whether the minimum cleanliness level has been achieved. Example 2: The surface contains rust and the mill scale has begun to flake. Rust Grade B The project specification requires “Thorough Hand or Power tool Cleaning.” St 2 The inspector uses the photographic standard labeled “B St 2” to inspect the surfaces to assess whether the minimum cleanliness level has been achieved. Example 3: The surface contains no mill scale and is completely rusted. General pitting is visible. Rust Grade D The project specification requires “Flame Cleaning.” F1 The inspector uses the photographic standard labeled “D F1” to inspect the surfaces to assess whether the minimum cleanliness level has been achieved.
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Using SSPC-VIS 3, “Guide and Reference Photographs for Steel Surfaces Prepared by Power and Hand Tool Cleaning” SSPC-VIS 3 is a collection of color reference photographs depicting seven initial conditions and four degrees of hand or power tool cleaning for each condition. Each color photograph is approximately 9 square inches. To use the SSPC VIS 3 visual guide and reference photographs follow these five basic steps. Step 1: Ask, “What does the steel look like (prior to surface preparation)?” The answer will yield an “Initial Condition” Step 2: Ask, “What level of surface cleanliness does the specification require?” The answer will yield a “Surface Cleanliness Code” Step 3: If the answer in Step 2 is “SP3,” ask, “What type of power tool was used to prepare the surface?” The answer will yield a “Power Tool Code” Step 4: Locate the reference photograph in the visual guide illustrating the initial condition (the “answer” to Step 1) and the reference photograph that represents the hand- or power tool-cleaned surfaces prepared to the specified degree of surface cleanliness (the “answer” to Step 2) using a specific type of power tool (the “answer” to Step 3, if appropriate). Step 5: Use the reference photograph selected in Step 4 to assess whether the prepared steel meets or exceeds the requirements of the specification. Let’s take a closer look at each of these five steps.
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Step 1: Ask, “What does the steel look like (prior to surface preparation)?” In order to use the visual guides and reference photographs properly, it is important that you determine what the existing steel looks like before it is prepared by hand- or power-tool cleaning. To do this, locate the reference photographs in the visual guide illustrating the seven possible initial conditions of the steel. We’ll call these “before photographs,” as they depict the condition of the steel “before” it was hand- or power-tool cleaned. The SSPC-VIS 3 guide and reference photographs illustrates seven such Initial Conditions, including: Condition A: Steel surface completely covered with adherent mill scale; little or no visible rust.
Condition B: Steel surface covered with both mill scale and rust.
Condition C: Steel surface completely covered with rust; little or no pitting visible.
Condition D: Steel surface completely covered with rust; pitting visible.
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Condition E: Previously painted steel surface; mostly intact, light-colored paint applied to a blast cleaned surface.
Condition F: Previously painted steel surface; mostly intact, zinc-rich paint applied to a blast cleaned surface.
Condition G: Paint system applied to mill scale bearing steel; system thoroughly weathered, blistered or stained. Select one of these “before” reference photographs that best illustrates the condition of the steel and write down the letter (A, B, C, D, E, F or G) before you proceed to Step 2. If the steel is represented by more than one condition, then write down the specific area of the structure and the corresponding condition letter for each area. Step 2: Ask, “What level of surface cleanliness does the specification require?” After you select a reference photograph that depicts the existing condition of the steel surfaces, you’ll need to look at the project specification to determine the degree of surface cleanliness required. This will appear in the project specification as one of four possible “levels:” SSPC-SP 2, SSPC-SP 3, SSPC-SP 11, or SSPC-SP 15. If the specification does not require one or more of these levels of surface cleanliness then the SSPC-VIS 3 visual guide and reference photographs cannot be used. Chart 1 provides the surface cleanliness codes and the corresponding levels of surface cleanliness depicted. Write down the surface cleanliness level required by the project specification using the code (e.g., if the specification requires hand Protective Coatings Inspector Training ©2015 SSPC
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Chart 1 – SSPC-VIS 3 Surface Cleanliness Guide Surface Cleanlinss Code SP2 SP3 SP11 SP15
Surface Cleanliness Level Depicted in Reference Color Photographs Hand Tool Cleaning Power Tool Cleaning Power Tool Cleaning to Bare Metal Commercial Grade Power Tool Cleaning
tool cleaning, write down SP2). At this point, you should have both a code for the initial condition (A, B, C, D, E, F or G) and a code for the surface cleanliness (SP2, SP3, SP11, or SP15). Step 3: If the answer to Step 2 was “SP3,” ask, “What type of power tool was used to prepare the surface?” After you select a reference photograph that depicts the existing condition of the steel surfaces (the “before photograph”), and determine the degree of surface cleanliness required by the project specification, you will need to determine the type of power tool used to prepare the surfaces. Note that this step is only necessary if the project specification requires SSPC-SP3, “Power Tool Cleaning.” That is, if hand tool cleaning (SSPC-SP2), power tool cleaning to bare metal (SSPC-SP11), or commercial grade power tool cleaning (SSPC-SP15) is specified, this step is not necessary. Chart 2 provides the power tool codes and the corresponding descriptions.
Photos depicting 2 power tool codes (SD & PWB)
Chart 2 – SSPC-VIS 3 Surface Cleanliness Guide Power Tool Code PWB SD
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Power Tool Description Power Wire Brush Sanding Disc
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Write down the power tool code that most closely approximates the tool being used (e.g., if a power wire brush was used, write down PWB). At this point, you should have a code for the initial condition (A, B, C, D, E, F or G), a code for the surface cleanliness (SP2, SP3, SP11, or SP15) and a third code for the type of power tool used, if SSPC-SP3 is specified. Step 4: Locate the reference photograph in the visual guide The SSPC-VIS 3 visual guide and reference photographs illustrates various levels of surface cleanliness (after hand- or power-tool cleaning is completed) for each of the conditions in Step 1. We’ll call these “after photographs.” Select the “after” reference photograph using the code put together in Step 3. Here are three examples: Example 1: If the steel surface contains both mill scale and rust, select Condition B. If the specification requires Power Tool Cleaning (SSPC-SP3), select level SP3. If a sanding disc is used, select power tool code SD. Now locate photograph B SP3 SD in the visual guide and reference photographs.
Condition B selected
SSPC-SP3 using a sanding disc selected
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Example 2: If the steel surface contains a mostly intact light-colored paint that was originally applied to a blast cleaned surface, select Condition E. If the specification requires Hand Tool Cleaning (SSPC-SP2), select level SP2. Now locate photograph E SP2 in the visual guide and reference photographs.
SSPC-SP2 hand tool cleaning selected
Condition E selected
Example 3: If the steel surface is rusted and pitted, select Condition D. If the specification requires Commercial Grade Power Tool Cleaning (SSPC-SP15), select level SP15. Now locate photograph D SP15 in the visual guide and reference photographs.
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SSPC-SP15 selected
Condition D selected
Note: Two additional photographs are found at the back of the guide and reference photographs. Two of the seven initial conditions (“E” and “F”) originally contained a surface profile. Both of these conditions were power tool cleaned to bare metal (SSPC-SP11) using non-woven discs to remove the coating to expose (restore) the original profile without creating a new one. These reference photographs contain an additional code (“R” designation, indicating Restored). For example, the reference photograph depicting Condition “E” that has been power tool cleaned to bare metal to expose (restore) the original surface profile contains the Code “E SP11/R.” Note that this is very difficult to achieve in practice. Step 5: Assess the prepared surfaces
Using SSPC-VIS 3
Use the reference photograph selected in Step 4 to determine whether the prepared surface(s) meet or exceed the specified level of surface cleanliness. If the prepared surfaces do not meet the specified level of cleanliness, then additional cleaning should be performed and the surfaces re-examined. Remember: Ambient lighting and the type of tool employed, as well as variations in the initial condition and the quality of the steel will
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TABLE 4A COMPARISON OF SSPC AND ISO SURFACE PREPARATION STANDARDS FOR POWER- AND HAND-TOOL CLEANED STEEL Surface Preparation Standard
SSPC
ISO
SP 11 Power Tool Cleaning to Bare Metal
SP 15 Commercial Grade Power Tool Cleaning
SP 3 Power Tool Cleaning
SP 2 Hand Tool Cleaning
St 3
St 2
Initial Condition of Steel Rust Condition
Reference Photographs
Description
SSPC-VIS 31
ISO 8501-12
A
intact mill scale
A SP 11
*
B
partially rusted mill scale
B SP 11
*
C
100% rusted, no pits
C SP 11
*
D
rusted and pitted
D SP 11
*
E
paint mostly intact
E SP 11, E SP 11/R
*
F
zinc-rich paint
F SP 11, F SP 11/R
*
G
deteriorated paint over mill scale
G SP 11
*
A
intact mill scale
*
*
B
partially rusted mill scale
B SP 15
*
C
100% rusted, no pits
C SP 15
*
D
rusted and pitted
D SP 15
*
E
paint mostly intact
E SP 15
*
F
zinc-rich paint
F SP 15
*
G
deteriorated paint over mill scale
G SP 15
*
A
intact mill scale
A SP 3/PWB, A SP 3/SD
*
B
partially rusted mill scale
B SP 3/PWB, B SP 3/SD
B St 3
C
100% rusted, no pits
C SP 3/PWB, C SP 3/SD
C St 3
D
rusted and pitted
D SP 3/PWB, D SP 3/SD
D St 3
E
paint mostly intact
E SP 3/PWB, E SP 3/SD
*
F
zinc-rich paint
F SP 3/PWB, F SP 3/SD
*
G
deteriorated paint over mill scale
G SP 3/PWB, G SP 3/SD
*
A
intact mill scale
A SP 2
*
B
partially rusted mill scale
B SP 2
B St 2
C
100% rusted, no pits
C SP 2
C St 2
D
rusted and pitted
D SP 2
D St 2
E
paint mostly intact
E SP 2
*
F
zinc-rich paint
F SP 2
*
G
deteriorated paint over mill scale
G SP 2
*
nophotograph photograph **==no 11 SSPC VIS 3 contains photographsforforSP SP11, 11,SPSP 15,SP SP3,3,and andSP SP2.2. SSPC-VIS 3 contains photographs 15, 22 The United Kingdom Standard 7079Part Part equivalenttotoISO ISO8501-1 8501-1and anddepicts depictsthe thedegrees degreesofofcleanliness cleanlinessofofunpainted steel. BS The United Kingdom Standard BSBS 7079 A1A1is isequivalent unpainted BS 7079toPart is equivalent to ISO and depicts the same degrees of cleanliness of previously 7079 Part A2steel. is equivalent ISOA2 8501-2 and depicts the8501-2 same degrees of cleanliness of previously painted steel. painted steel.
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impact the appearance of the prepared surface and the perceived level of cleanliness. The SSPC visual guides and reference photographs were designed as a guide, and the written standards prevail in the event of a dispute. Note that because of the subjectivity involved in cleanliness assessments, it may be worthwhile to establishing a project-specific cleanliness standard (using the visual guides and reference photographs for guidance) before the job begins. This can help all parties involved gain a mutual understanding of the desired level of cleanliness. Dry Abrasive Blast Cleaning Blast cleaning using dry abrasive media is perhaps the most common method of preparing a surface for coating. Abrasive blast cleaning can be used to roughen an existing coating for subsequent overcoating or to completely remove the existing corrosion products, coating, and mill scale. Abrasive blast cleaning is the most productive of all surface preparation methods. Thousands of square feet/meters of surface can be prepared for coating in a single work shift. The hardness and mass of the abrasive media combined with the velocity of the abrasive as it exits a nozzle at speeds exceeding 805 kilometers per hour (500 miles per hour) using air pressures up to 862 KPa (125 psi) generates high levels of energy. As the abrasive media impacts the surface with this energy, it can remove existing coating layers, corrosion and mill scale, while simultaneously increasing the surface area of the steel by generating a surface profile or anchor pattern. The level of cleanliness that is achieved is ultimately determined by the distance that the nozzle is held from the surface and the “dwell time” that the operator employs. The depth and shape of the surface profile is determined by the type and size of the abrasive media employed, as well as the hardness of the surface being prepared. Therefore, selecting the correct type and size of abrasive is critical. Selecting too small of an abrasive size will generate a surface profile that is too shallow, and selecting too large of an abrasive will create a surface profile that is too deep. The abrasive type and size ultimately selected should be demonstrated prior to production to verify that the specified surface profile depth and shape can be achieved. A traditional dry abrasive blast cleaning set-up is illustrated in BlastOff 2, published by Clemco Industries (reproduced below). This more traditional set-up consists of a source of compressed air (of sufficient Protective Coatings Inspector Training ©2015 SSPC
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capacity to provide an adequate volume of air to support the nozzle size, hose length, air pressure and number of operators), an ASMEcoded abrasive hopper equipped with an air moisture and oil separator, a metering valve (located at the base of the hopper to meter abrasive from the hopper into the blast hose), a blast hose to carry the metered abrasive and compressed air to the nozzle (equipped with external hose couplings, safety wires and/or cables [whip checks]) and a blast nozzle. Safety is paramount to the blast cleaning process. In the U.S., the Occupational Safety and Health Administration (OSHA) has specific regulations governing abrasive blast cleaning that include hand, foot and skin protection from abrasive ricochet, respiratory protection (Type CE blast helmet under positive pressure, with tested and certified Grade D breathing air), and a pneumatic or electrically operated “deadman,” which automatically stops the flow of air pressure and abrasive in the event that the operator loses control of the blast nozzle. Projects employing “recycled” abrasives will typically use blast pots in conjunction with vacuum equipment for collecting spent abrasive and recycling equipment for separatioin the smaller particles and debris from the reusable abrasive. Blast Cleaning Productivity There are many factors that can impact the productivity of abrasive blast cleaning operations. First, the compressor must be adequately sized to provide the volume of air (measured in cubic feet per Hypodermic Needle Pressure Gage minute or CFM) necessary to maintain the desired nozzle pressure. Optimum blast nozzle pressure is 620-690 KPa (90-100 psi), but can be increased to 827-861 KPa (120-125 psi) if a recyclable abrasive like steel grit is being used. According to Clemco, a 69 KPa (10 psi) reduction in blast nozzle pressure equates to a 15% reduction in productivity, so maintaining nozzle pressure is paramount to Protective Coatings Inspector Training ©2015 SSPC
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blast cleaning productivity. Blast nozzle pressure can be measured using a hypodermic needle pressure gage. The needle of the gage is inserted into the blast hose at a 45o angle (in the direction of air and abrasive flow) as close as feasible to the blast nozzle. The deadman valve (automatic system shutdown safety lever) is closed so that both abrasive and air begin to flow. The operational pressure is read from the gage dial. If multiple operators will be using the same source of compressed air, it is important that all deadman controls be closed simultaneously, in order to obtain a representative pressure reading. Blast pressure can be increased by reducing the size of the blast nozzle or better yet, increasing the capacity of the compressed air source. Blast-Off 2 by Clemco contains several charts on the size of the compressor required to maintain pressure for a given nozzle size. These charts are shown on the following pages. Blast cleaning productivity is also affected by: • • • • •
The condition of the surface (number and relative brittleness of coating layers, stratified or pack rust verses surface rusting, etc.), The abrasive type and size selected, The distance from the nozzle to the surface, The angle at which the operator holds the nozzle to the surface, and The flow of the abrasive from the hopper into the blast hose.
In general, brittle coatings are easier to remove than softer coatings or coatings with elasticity, as the abrasive tends to bounce off, rather than fracture soft/elastomeric coatings. Harder abrasives tend to remove coatings faster than softer ones, and smaller abrasives are generally more productive than larger abrasives, as smaller abrasives produce a higher number of impacts per area and in turn clean faster. However the abrasive must have sufficient mass to remove the existing coating system and produce the required profile depth, which is primarily dictated by the size of the abrasive. Nozzle distance will vary, and is dependent upon the difficulty in coating/rust removal. In general, the blast nozzle distance is maintained between 30-46 cm (12 and 18 inches) from the surface (closer for tenacious coatings and further away if coatings are easily removed). Distances greater than 60 cm (24”) are generally not recommended. The angle that the blast nozzle is held to the surface
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will also vary and is operator dependent. In general, mill scale and rust are best removed when the nozzle is maintained at an 80-90° angle, while old coatings are removed more easily if the nozzle is held 45-60° to the surface. Finally, the flow of abrasive from the hopper into the blast hose can impact productivity. If the metering valve is set too lean, there will be an insufficient quantity of abrasive exiting the nozzle, reducing productivity. Conversely, if the valve is set too rich, the blast hose and nozzle will become flooded with abrasive, also decreasing productivity. The metering valve should be set by the operator to achieve the optimum abrasive flow.
U.S. Standard Compressed Air and Abrasive Consumption Nozzle Orifice No. 2 (1/8”)
No. 3 (3/16”)
No. 4 (1/4”)
No. 5 (5/16”)
No. 6 (3/8”)
No. 7 (7/16”)
No. 8 (1/2”)
50 11 .67 67 2.5 26 1.50 150 6 47 2.68 268 11 77 4.68 468 18 108 6.68 668 24 147 8.96 896 33 195 11.60 1160 44
60 13 .77 77 3 30 1.71 171 7 54 3.12 312 12 89 5.34 534 20 126 7.64 764 28 170 10.32 1032 38 224 13.36 1336 50
Pressure at the Nozzle (psi) 70 80 90 100 15 17 18.5 20 .88 1.01 1.12 1.23 88 101 112 123 3.5 4 4.5 5 33 38 41 45 1.96 2.16 2.38 2.64 196 216 238 264 8 9 10 10 61 68 74 81 3.54 4.08 4.48 4.94 354 408 448 494 14 16 17 18 101 113 126 137 6.04 6.72 7.40 8.12 604 672 740 812 23 26 28 31 143 161 173 196 8.64 9.60 10.52 11.52 864 960 1052 1152 32 36 39 44 194 217 240 254 11.76 13.12 14.48 15.84 1176 1312 1148 1584 44 49 54 57 252 280 309 338 15.12 16.80 18.56 20.24 1512 1680 1856 2024 56 63 69 75
125 25 1.52 152 5.5 55 3.19 319 12 98 6.08 608 22 168 9.82 982 37 237 13.93 1393 52 314 19.13 1913 69 409 24.59 2459 90
140 28 1.70 170 6.2 62 3.57 357 13 110 6.81 681 25 188 11.0 1100 41 265 15.60 1560 58 352 21.63 2163 77 458 27.54 2754 101
Air (in cfm) Abrasive & HP requirements Air (cfm) Abrasive (cu.ft./hr. & lbs./hr.) Compressor hp Air (cfm) Abrasive (cu.ft./hr. & lbs./hr.) Compressor hp Air (cfm) Abrasive (cu.ft./hr. & lbs./hr.) Compressor hp Air (cfm) Abrasive (cu.ft./hr. & lbs./hr.) Compressor hp Air (cfm) Abrasive (cu.ft./hr. & lbs./hr.) Compressor hp Air (cfm) Abrasive (cu.ft./hr. & lbs./hr.) Compressor hp Air (cfm) Abrasive (cu.ft./hr. & lbs./hr.) Compressor hp
(Based on abrasive with a density of 100 pounds per cubic foot.)
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Metric Compressed Air and Abrasive Consumption Nozzle Orifice 5mm (3/16”) 6.5mm (1/4”) 8mm (5/16”) 9.5mm (3/8”) 11mm (7/16”) 12.5mm (1/5)
3.5 350
4.2 420
4.9 490
5.6 560
6.3 630
7.0 700
8.6 860
10.3 1035
0.73 68 4.5 1.31 122 7.9 2.16 212 13.1
0.84 78 5.3 1.51 142 9.0 2.50 242 15.0
0.92 89 5.6 1.71 161 10.1 2.83 274 19.1
1.06 98 6.4 1.90 185 11.6 3.16 305 20.2
1.15 108 7.1 2.08 203 12.4 3.53 336 21.0
1.26 120 7.5 2.27 224 13.5 3.84 368 22.9
1.54 145 9.0 2.75 276 16.2 4.71 445 27.5
1.82 174 10.8 3.22 325 19.4 5.57 534 33.0
3.02
3.53
4.00
4.50
4.85
5.50
6.64
7.79
Requirements: Air (m3/min) Abrasive (kg/h) * & kW Air (m3/min) Abrasive (kg/h) kW Air (m3/min) Abrasive (kg/h) kW Air (m3/min) Abrasive (kg/h) kW Air (m3/min)
303 18.0 4.12 406 24.8 5.46 526 32.6
347 21.0 4.76 468 28.5 6.28 606 37.5
392 24.0 5.44 533 32.6 7.06 686 42.0
435 27.0 6.09 595 36.4 7.85 762 46.9
477 28.9 6.73 657 40.1 8.65 842 51.8
573 33.0 7.11 719 42.4 9.46 918 56.3
632 39.6 8.80 876 50.9 11.46 1115 67.6
758 47.5 10.48 1040 61.1 13.45 1333 81.1
Abrasive (kg/h) kW Air (m3/min) Abrasive (kg/h) kW Air (m3/min) Abrasive (kg/h) kW
Pressure at the Nozle (bar & kPa)
* Based on abrasive with a density of 1.5 kg per liter.
ISO Sa 1: Light Blast Cleaning “When viewed without magnification, the surface shall be free from visible oil, grease and dirt, and from poorly adhering mill scale, rust, paint coatings and foreign matter.” ISO Sa 2: Thorough Blast Cleaning “When viewed without magnification, the surface shall be free from visible oil, grease and dirt, and from most of the mill scale, rust, paint coatings and foreign matter. Any residual contamination shall be firmly adhering.”
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ISO Sa 2 ½: Very Thorough Blast Cleaning “When viewed without magnification, the surface shall be free from visible oil, grease and dirt, and from mill scale, rust, paint coatings and foreign matter. Any remaining traces of contamination shall show only as stains in the form of spots or stripes.” ISO Sa 3: Blast Cleaning to Visually Clean Steel “When viewed without magnification, the surface shall be free from visible oil, grease and dirt, and shall be free from mill scale, rust, paint coatings and foreign matter. It shall have a uniform metallic colour.” SSPC Abrasive Blast Cleaning Standards SSPC has published five abrasive blast cleaning standards. They vary in the level of surface cleanliness required, and are described below from the lowest degree of cleaning to the highest. There is no surface profile requirement for any of the abrasive blast cleaning standards. Therefore, the project specification must stipulate the required depth of the surface profile. Each of the five abrasive blast surface cleanliness standards contains both direct and indirect requirements. The “direct” requirements vary depending on the degree of cleanliness described by each standard. These requirements are detailed in each of the five sections that follow. However, the “indirect” requirements are common to all five of the standards. The indirect requirements invoked by the abrasive blast cleaning standards include removal of visible grease, oil and other contaminants (per SSPC-SP1) prior to abrasive blast cleaning (described earlier); compressed air cleanliness (per ASTM D4285) and cleanliness of the abrasive employed. The compressed air cleanliness test and the abrasive cleanliness tests are described later in this module. These requirements are invoked by each of the abrasive blast cleanliness standards, independent of whether the contract documents invoke the SSPC abrasive specifications or the ASTM air cleanliness test method.
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The appearance of steel surfaces prepared by abrasive blast cleaning is influenced by many factors, including: the amount and direction of available lighting during inspection; the type of abrasive used by the contractor and the amount of embedment left in the surface profile by the abrasive; the shape and depth of the surface profile; and the cleaning mechanism (open nozzle verses automated [centrifugal] or deck blast units). In addition, deck blast units can leave streaks on the surface from the machine itself, which is not considered staining, since it was not on the surface originally. Steel can also contain “manufacturing stains” which cannot be removed by abrasive blast cleaning. The inspector must not confuse manufacturing stains with stains from existing mill scale, rust or paint. Flash rusting (rust back) of the prepared surfaces is not permitted by the SSPC abrasive blast cleaning standards. Flash rust represents a loosely adhering layer, which can interfere with coating adhesion and may propagate under film corrosion. Flash rust can be detected visually or by wiping the surface with a clean white rag. Any flash rust must be removed from the surface prior to coating application. The amount of staining permitted by each of four abrasive blast surface cleanliness standards described below (all except SSPC-SP7/ NACE No. 4) is based on each 58 cm2 (9 in2) of prepared surface. This size area was selected by SSPC and NACE based on the approximate size of the photographs in the SSPC VIS 1 Guide and Reference Photographs (each photograph is approximately 8 cm x 8 cm [3” x 3”]). Two of the five abrasive blast surface cleanliness standards described below (SSPC-SP6/NACE No. 3 and SSPC-SP10/NACE No. 2) invoke a maximum staining criterion. Determining whether the amount of staining remaining does or does not exceed the maximum amount allowed by SSPC-SP6 and SP10 is done visually, which can be subjective. Establishing a project-specific cleanliness standard may help to better define the level of cleanliness required on a given structure. The area should be representative of the structure, and should be preserved as a reference in the event of a dispute later during the cleaning operations. Many contracts require the establishment of a project-specific cleanliness test area. This is described in more detail later in this module.
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When mutually agreed upon or when invoked by the contract documents, ISO 8501-1 or SSPC VIS 1 photographic references can be used to help evaluate the cleanliness of surfaces prepared by abrasive blast cleaning. While the photographic references in ISO 8501-1 or SSPC VIS 1 or in will rarely match the actual surfaces prepared by the contractor, they serve as an excellent tool to help those evaluating the degree of cleanliness achieved to “calibrate” their eyes, and they are invaluable for establishing a jobsite cleanliness standard. The proper use of these visual guides is described later in this module. SSPC-SP 7/NACE No. 4, Brush-off Blast Cleaning SSPC-SP 7/NACE No. 4, “Brush-off Blast Cleaning” requires the removal of all loosely adhering rust, mill scale and paint by “lightly sweeping” the surface with the abrasive media. The remaining materials are considered tightly-adhering if they cannot be lifted using the blade of a dull putty knife. The project specification may require that the edges of intact paint to be feathered to facilitate a smooth transition, and to prevent lifting of the edge by the application of subsequent coating layers. While there is no surface profile requirement for brush-off blast cleaning, some surface roughening will be created by the abrasive impacting the surface. Brush-off blast cleaning may fracture but not necessarily loosen aged, brittle coatings. Subsequent application of coating layers to this “damaged” surface may result in disbonding of the coating film from the substrate. Use of SSPC-SP 7/NACE No. 4 to roughen existing surfaces must be done with great care, and may not be the optimal choice if the existing coating is old or has become embrittled. SSPC-SP 14/NACE No. 8, Industrial Blast Cleaning SSPC-SP 14/NACE No. 8, “Industrial Blast Cleaning” requires the removal of all loosely adhering rust, mill scale and paint from the surface. A minimum of 90% of all tightly adhering materials must also be removed. Up to 10% of each 58 cm2 (9 square inches) of prepared surface can contain evenly distributed islands of intact mill scale, rust or paint. The remaining materials are considered intact if they cannot be lifted using the blade of a dull putty knife. Staining from existing materials is unlimited. The project specification may require that the edges of intact paint to be feathered to facilitate a smooth transition,
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and to prevent lifting of the edge by the application of subsequent coating layers.
SSPC-SP 6/NACE No. 3, Commercial Blast Cleaning SSPC-SP 6/NACE No. 3, “Commercial Blast Cleaning” requires the removal of all loosely and all tightly adhering mill scale, rust and paint from the surface. Evenly distributed staining from rust, paint and mill scale is permitted, provided it does not exceed 33% (one-third) of each 58 cm2 (9 square inches) of prepared surface. The difference between a “stain” from rust, paint or mill scale can be hard to differentiate from actual rust paint or mill scale left behind. While guides are available, they too are visual and can be difficult to use to determine the presence of actual materials left on the surface verses staining. Some specifications reference the use of a small knife blade that is used to lightly scratch the surface. If the surface is lightly scratched and a powder or flakes are created, then the surface does not meet the SP6/ NACE No. 3 definition. If, on the other hand, the light scraping does not produce a powder of small flakes, then the surface is considered stained and is acceptable, as long as the staining does not exceed 33% of each 58 cm2 (9 square inches) of prepared surface area. SSPC-SP 10/NACE No. 2, Near-White Blast Cleaning SSPC-SP 10/NACE No. 2, “Near-White Blast Cleaning” requires the removal of all loosely and all tightly adhering mill scale, rust and paint from the surface. Evenly distributed staining from rust, paint and mill scale is permitted, provided it does not exceed 5% of each 58 cm2 (9 square inches) of prepared surface. The difference between a “stain” from rust, paint or mill scale can be hard to differentiate from actual rust paint or mill scale left behind. While guides are available, they too are visual and can be difficult to use to determine the presence of actual materials left on the surface verses staining. Some specifications reference the use of a small knife blade that is used to lightly scratch the surface. If the surface is lightly scratched and a powder or flakes is created, then the surface does not meet the SP10/ NACE No. 2 definition. If on the other hand the light scraping does not produce a powder of small flakes, then the surface is considered
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TABLE 4B COMPARISON OF SSPC AND ISO SURFACE PREPARATION STANDARDS FOR BLAST CLEANED STEEL Surface Preparation Standard SSPC/NACE
SP 5/NACE No. 1 White Metal Blast Cleaning
SP 10/NACE No. 2 Near-White Blast Cleaning
SP 6/NACE No. 3 Commercial Blast Cleaning
ISO1
Sa 3
Sa 2 1/2
Sa 2
SP 14/NACE No. 8 Industrial Blast Cleaning
SP 7/NACE No. 4 Brush-Off Blast Cleaning
Sa 1
Initial Condition of Steel Rust Condition
Reference Photographs
Description
SSPC-VIS 12/SSPC-VIS 5
ISO 8501-1
A
intact mill scale
A SP 5, A SP 5-N1, A SP 5-N2, A SP 5-N3 A SP 5-M1, A SP 5-M2,A SP 5-M33
A Sa 34
B
partially rusted mill scale
B SP-5
B Sa 34
C
100% rusted, no pits
C SP-5
C Sa 34
D
rusted and pitted
D SP-5
D Sa 3
G
deteriorated paint over mill scale
G1 SP 5, G2 SP 5, G3 SP 5, G1 SP 5 P, G1 SP 5 H, G1 SP 5 L, G1 SP 5 D, G3 SP 5 P, G3 SP 5 H, G3 SP 5 L, G3 SP 5 D
*
A
intact mill scale
A SP 10
A Sa 2 1/2
B
partially rusted mill scale
B SP-10
B Sa 2 1/2
C
100% rusted, no pits
C SP-10, C WAB-105
C Sa 2 1/2
D
rusted and pitted
D SP-10, D WAB-10
D Sa 2 1/2
G
deteriorated paint over mill scale
G1 SP 10, G2 SP 10, G3 SP 10
*
A
intact mill scale
*
*
B
partially rusted mill scale
B SP-6
B Sa 2
C
100% rusted, no pits
C SP-6, C WAB-6
C Sa 2
D
rusted and pitted
D SP-6, D WAB-6
D Sa 2
G
deteriorated paint over mill scale
G1 SP 6, G2 SP 6, G3 SP 6
*
A
intact mill scale
*
*
B
partially rusted mill scale
*
*
C
100% rusted, no pits
*
*
D
rusted and pitted
*
*
G
deteriorated paint over mill scale
G1 SP 14, G2 SP 14, G3 SP 14
*
A
intact mill scale
B
partially rusted mill scale
*
*
B SP-7
B Sa 1
C
100% rusted, no pits
C SP-7
C Sa 1
D
rusted and pitted
D SP-7
D Sa 1
G
deteriorated paint over mill scale
G1 SP 7, G2 SP 7, G3 SP 7
*
* no photograph 1 ISO standards Sa 3, Sa 2 1/2, Sa 2, Sa 1, St 2 and St 3 approximate the corresponding SSPC standards. * = no2 photograph 1 SSPC-VIS photographs 5, SP SP 7, SP 10,the andcorresponding SP 14. ISO3 standards Sa13,contains Sa 2 1/2, Sa 2, Sa 1,for St SP 2 and St 36,approximate SSPC standards. 2 Alternate non-metallic abrasives: A SP 5-N1, A SP 5-N2, SP SP 5-N3 SSPC-VIS 1 contains photographs for SP 5, SP 6, SP 7, SP 10,Aand 14. 3 Alternate metallic abrasives: 5-M1, A SP 5-M2, A SP 5-M3 Alternate non-metallic abrasives: AA SPSP 5-N1, A SP 5-N2, A SP 5-N3 4 ISOmetallic 8501-1abrasives: photographs (1978 through may not adequately illustrate the corresponding SSPC surface preparation Alternate A SP 5-M1, A SP 1989 5-M2,printing) A SP 5-M3 4 ISO photograph B Sa 21989 shows dark areas thatadequately could be interpreted as mill scale and, therefore, represents SSPC-SP 14 ISO 8501-1 photographsillustrating (1978 through printing) may not illustrate the corresponding SSPC surface preparation and does not represent SSPC-SP ISO photograph illustrating B Sa 2 shows6.dark areas that could be interpreted as mill scale and, therefore, represents SSPC-SP 14 and ISOrepresent photographs illustrating does not SSPC-SP 6. A Sa 3, B Sa 3 and C Sa 3 do not adequately illustrate the surface texture of typically blast cleaned steel. The United illustrating Kingdom Standard A13isdo equivalent to ISO illustrate 8501-1 and degrees of cleanliness of unpainted steel. ISO photographs A Sa 3, BBS Sa7079 3 andPart C Sa not adequately the depicts surfacethe texture of typically blast cleaned steel.The 7079 Part A2 is equivalent to ISO 8501-2 and depicts sameand degrees ofthe cleanliness steel. steel. BS 7079 UnitedBS Kingdom Standard BS 7079 Part A1 is equivalent to ISOthe 8501-1 depicts degrees of of previously cleanlinesspainted of unpainted 5 5 photographs of wet blastsame cleaning are indicated by WAB. Part A2SSPC-VIS is equivalent to ISO 8501-2 andabrasive depicts the degrees of cleanliness of previously painted steel. 5 SSPC-VIS 5 photographs of wet abrasive blast cleaning are indicated by WAB.
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stained and is acceptable, as long as the staining does not exceed 5% of each 58 cm2 (9 square inches) of prepared surface area. SSPC-SP 5/NACE No. 1, White Metal Blast Cleaning SSPC-SP 5/NACE No. 1, “White Metal Blast Cleaning” requires the removal of all loosely and all tightly adhering mill scale, rust and paint from the surface. Staining from rust, paint or mill scale is not permitted by the SSPC-SP 5/NACE No. 1 surface cleanliness standard.
Using SSPC-VIS 1, “Guide and Reference Photographs for Steel Surfaces Prepared by Dry Abrasive Blast Cleaning” SSPC-VIS 1 is a collection of color reference photographs depicting various initial conditions and different levels of dry abrasive blast cleaning. Silica sand was used to prepare the steel for the visual guides. Most of the color reference photographs are approximately 9 square inches. Some photographs are slightly smaller in size. To use the SSPC VIS 1 Guide and Reference Photographs, follow these four basic steps: Step 1: Ask, “What does the steel look like (prior to surface preparation)?” The answer will yield an “Initial Condition” Step 2: Ask, “What level of surface cleanliness does the specification require?” The answer will yield a “Surface Cleanliness Code”
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Step 3: Locate the reference photograph in the visual guide illustrating the initial condition (the “answer” to Step 1) and the reference photograph that represents the specified degree of surface cleanliness (the “answer” to Step 2). Step 4: Use the reference photograph selected in Step 3 to assess whether the prepared steel meets or exceeds the requirements of the specification. Let’s take a closer look at each of these four steps. Step 1: Ask, “What does the steel look like (prior to surface preparation)?” In order to use the visual guide properly, it is important that you determine what the existing steel looks like before it is prepared by abrasive blast cleaning. To do this, locate the reference photographs in the visual guide illustrating the seven possible initial conditions of the steel. We’ll call these “before photographs,” since they depict the condition of the steel “before” it was abrasive blast cleaned. The SSPC-VIS 1 Guide and Reference Photographs illustrates seven such Initial Conditions, including: Condition A: Steel surface completely covered with adherent mill scale; little or no visible rust (a.k.a. Rust Grade A).
Condition B: Steel surface covered with both mill scale and rust (a.k.a. Rust Grade B).
Condition C: Steel surface completely covered with rust; little or no pitting visible (a.k.a. Rust Grade C). Protective Coatings Inspector Training ©2015 SSPC
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Condition D: Steel surface completely covered with rust; pitting visible (a.k.a. Rust Grade D).
Condition G : Weathered coating system over mill scale with extensive pinpoint rusting. 1
Condition G : Weathered coating system over mill scale with moderate pitting. 2
Condition G : Weathered coating system over mill scale with severe pitting. 3
Select one of these “before” reference photographs that best illustrates the condition of the steel and write down the letter (A, B, C, D for unpainted steel and G , G , G for previously painted steel) before you proceed to Step 2. If the steel is represented by more than one condition, then write down the specific area of the structure and the corresponding condition letter for each area. 1
2
3
Step 2: Ask, “What level of surface cleanliness does the specification require?” After you select a reference photograph that depicts the existing condition of the steel surfaces (the “before photograph”), you’ll need to look at the project specification to determine the degree of surface Protective Coatings Inspector Training ©2015 SSPC
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cleanliness required. The degree of surface cleanliness will appear in the project specification as one of five possible “levels,” including SSPC-SP 7, Brush-off Blast; SSPC-SP 14, Industrial Blast; SSPCSP 6, Commercial Blast; SSPC-SP 10, Near-White Metal Blast; or SSPC-SP 5, White Metal Blast. If the specification does not require one or more of these four levels of surface cleanliness (or the NACE counterpart), then the SSPC-VIS 1 Guide and Reference Photographs cannot be used. Write down the surface cleanliness level required by the project specification using the code (e.g., if the specification requires a Near-White blast, write down SP 10). You should have both a code for the initial condition (A, B, C, D, G , G or G ) and a code for the surface cleanliness (SP 7, SP 14, SP 6, SP 10 or SP 5). 1
2
3
Step 3: Locate the reference photograph in the visual guide. SSPC-VIS 1 illustrates various levels of surface cleanliness (after abrasive blast cleaning is completed) for each of the “before photographs” in Step 1. Chart 1 provides the combinations of initial conditions (before photographs) and surface cleanliness levels (after photographs). Select the reference photograph in the visual guide by putting together the code for the initial condition (from column 1 of Chart 3) and the code for the specified surface cleanliness level (from column 2 of Chart 3). Chart 3 - SSPC-VIS 1 Surface Cleanliness Guide Rust Grade
Surface Cleanliness Levels Depicted in the Reference Color Photographs
A
Near-White Metal Blast (SP10) and White Metal Blast (SP5)
B
Brush-off Blast (SP7); Commercial blast (SP6); Near-White Metal Blast (SP10); and White Metal Blast (SP5)
C
Brush-off Blast (SP7); Commercial Blast (SP6); Near-White Metal Blast (SP10); and White Metal Blast (SP5)
D
Brush-off Blast (SP7); Commercial Blast (SP6); Near-White Metal Blast (SP10); and White Metal Blast (SP5)
G1
Brush-off Blast (SP7); Industrial Blast (SP14); Commercial Blast (SP6); Near-White Metal Blast (SP10); and White Metal Blast (SP5)
G2
Brush-off Blast (SP7); Industrial Blast (SP14); Commercial Blast (SP6); Near-White Metal Blast (SP10); and White Metal Blast (SP5)
G3
Brush-off Blast (SP7); Industrial Blast (SP14); Commercial Blast (SP6); Near-White Metal Blast (SP10); and White Metal Blast (SP5)
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Here are two examples: Example 1: If the steel surface is completely rusted but no pitting is visible, select Condition C. If the specification requires a Commercial Blast, select level SP6. Put the two codes together to arrive at the complete code (C SP6). Now locate the section of the SSPC-VIS 1 guide that contains the “before” photograph C and the four “after” photographs of the four levels of surface cleanliness. Select the “after” photograph that contains the complete code (e.g., C SP6). Use this reference photograph in Step 4 below. Rust Grade C selected
Commercial Blast (SSPCSP 6) selected
Example 2: If the steel contains a weathered coating system over mill scale with moderate pitting, select Condition G2. If the specification requires an Industrial Blast, select level SP14. Put the two codes together to arrive at the complete code (G2 SP14). Now locate the Protective Coatings Inspector Training ©2015 SSPC
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section of the SSPC-VIS 1 guide that contains the “before” photograph G2 and the “after” photographs of the five levels of surface cleanliness. Select the “after” photograph that contains the complete code (e.g. G2 SP14). Use this reference photograph in Step 4 below.
Condition G2 selected
Industrial Blast (SSPC-SP 14) selected
Step 4: Assess the prepared surfaces Use the reference photograph selected in Step 3 to determine whether the prepared surface(s) meet or exceed the specified level of surface cleanliness. If the prepared surfaces do not meet the specified level of cleanliness, then additional abrasive blast cleaning should be performed and the surfaces re-examined.
Using SSPC-VIS 1
Remember: Ambient lighting, the abrasive employed and tendency for embedment, as well as variations in the rust grade and the quality of the steel will impact the appearance of the prepared surface and the perceived level of cleanliness. The SSPC visual guides and reference photographss were designed as a guide, but the written standards prevail in the event of a dispute. Note that because of the subjectivity involved in cleanliness assessments, it may be worthwhile to establish a project-specific cleanliness standard (using the visual guides and reference photographs for guidance) before the job begins. This can
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help all parties involved gain a mutual understanding of the desired level of cleanliness. Note: There are two Appendices to the Visual Guide and Reference Photographs. Appendix A contains six color reference photographs. All of these photographs represent a Condition A surface (steel surface completely covered with adherent mill scale; little or no visible rust) dry abrasive blast cleaned to SSPC-SP5 (White Metal Blast). Six abrasive types were employed to create the images for the photographs: three nonmetallic abrasives (denoted N1, N2, and N3) and three metallic abrasives (denoted M1, M2, and M3). While these photographs are not part of the visual guide, they illustrate the variation in color, texture and general appearance of a “White Metal Blast” that can result from the abrasive selected for a project. Appendix B contains ten color reference photographs. Five reference photographs represent a Condition G1 surface (weathered coating system over mill scale with extensive pinpoint rusting) and five represent a Condition G2 surface (weathered coating system over mill scale with moderate pitting). All ten reference photographs depict dry abrasive blast cleaned to SSPC-SP5 (White Metal Blast). Two reference photographs (one of each condition) depict a 1 mil surface profile, and two reference photographs depict a 4 mil surface profile. Additional photographs illustrate the effect of the light angle (“H” for high and “L” for low) and diffused (“D”). Wet Abrasive Blast Cleaning
Wet Abrasive Blast Nozzle
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Wet abrasive blast cleaning may be used when airborne dust control is required by the specification or by local air quality regulations. Some facility owners specify the use of wet abrasive blast cleaning in order to reduce the complexity of the containment and ventilation system required on a given project. In addition, wet abrasive blast cleaning is an engineering control that can reduce airborne worker exposures to toxic metals during the coating removal processes. Three variations of this surface
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preparation method exist: waterjetting with abrasive induction, abrasive blasting with water induction and the use of a water collar. All three methods employ a mineral or slag type abrasive media. The latter two methods (abrasive blasting with water induction and the use of a water collar) rely on the abrasive to perform the majority of the surface preparation work. The water is used to suppress the dust and to remove some chemical contamination from the surfaces, if present. The former method (waterjetting with abrasive induction) uses high pressure water as the removal media, while the abrasive inducted into the water stream etches the surfaces and accelerates the removal process. Naturally, the water used in this method will also suppress any airborne dust that is generated. Any surface preparation method that incorporates water is going to cause carbon steel surfaces to flash rust. Therefore, the specifier may require the use of a rust inhibitor (that is compatible with the coating system to be applied to the prepared surfaces), or simply accept the flash rusting that occurs and select a coating system that is tolerant in the given environment. The SSPC visual guides and reference photographs (discussed later in this module) for wet abrasive blast cleaning illustrate three levels of flash rusting (light, medium and heavy), so that the degree of tolerable surface rust can be judged by the inspector. In addition to flash rusting, wet abrasive tends to attach itself to the prepared surfaces, which requires the operator to thoroughly rinse the surfaces with clean (perhaps rust-inhibited) water to ensure that abrasive debris is not coated over. The standards that cover wet abrasive blast cleaning are: SSPC-SP 5 (WAB)/NACE WAB-1, White Metal Wet Abrasive Blast Cleaning White Metal WAB Surface: A white metal WAB surface, when viewed without magnification, shall be free of all visible oil, grease, dust, dirt, mill scale, rust, coating, corrosion products, and other foreign matter.
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SSPC-SP 10 (WAB)/NACE WAB-2, Near-White Metal Wet Abrasive Blast Cleaning Near-White Metal WAB Surface: A near-white metal WAB-cleaned surface, when viewed without magnification, shall be free of all visible oil, grease, dust, dirt, mill scale, rust, coating, corrosion products, and other foreign matter. Random staining shall be limited to no more than 5% of each unit area of the surface (approximately 5,800 mm2 [9.0 in2]; i.e., a square 76 mm x 76 mm [3.0 in x 3.0 in]), and may consist of light shadows, slight streaks, or minor discolorations caused by stains of rust, stains of mill scale, or stains of previously applied coating. SSPC-SP 6 (WAB)/NACE WAB-3, Commercial Wet Abrasive Blast Cleaning Commercial WAB Surface: A commercial WAB-cleaned surface, when viewed without magnification, shall be free of all visible oil, grease, dust, dirt, mill scale, rust, coating, corrosion products, and other foreign matter. Random staining shall be limited to no more than 33% of each unit area of surface (approximately 5,800 mm2 [9.0 in2] (i.e., a square 76 mm x 76 mm [3.0 in x 3.0 in]), and may consist of light shadows, slight streaks, or minor discolorations caused by stains of rust, stains of mill scale, or stains of previously applied coating. SSPC-SP 14 (WAB)/NACE WAB-8, Industrial Wet Abrasive Blast Cleaning Industrial WAB Cleaned Surface: An Industrial WAB cleaned surface, when viewed without magnification, shall be free of all visible oil, grease, dirt, dust, loose mill scale, loose rust, and loose coating. Traces of tightly adherent mill scale, rust, and coating residues are permitted to remain on up to 10% of each unit area of the surface. Mill scale, rust, and coating are considered tightly adherent if they cannot be removed by lifting with a dull putty knife after abrasive blast cleaning has been performed. Shadows, streaks, and discolorations caused by stains of rust, stains of mill scale, and stains of previously applied coating may be present on the remainder of the surface. SSPC-SP 7 (WAB)/NACE WAB-4, Brush-Off Wet Abrasive Blast Cleaning Brush-Off WAB Surface: A brush-off WAB cleaned surface, when viewed without magnification, shall be free of all visible oil, grease, dirt, dust, loose mill scale, loose rust, and loose coating. Tightly Protective Coatings Inspector Training ©2015 SSPC
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adherent mill scale, rust, and coating may remain on the surface. Mill scale, rust, and coating are considered tightly adherent if they cannot be removed by lifting with a dull putty knife after abrasive blast cleaning has been performed. The entire surface shall be subjected to the wet abrasive blast. The remaining mill scale, rust, or coating shall be tight. Flecks of the underlying steel need not be exposed whenever the original substrate consists of intact coating.
Using SSPC-VIS 5/NACE VIS 9, “Guide and Reference Photographs for Steel Surfaces Prepared by Wet Abrasive Blast Cleaning” SSPC-VIS 5/NACE VIS 9 is a collection of color reference photographs depicting two initial conditions and two degrees of wet abrasive blast cleaning for each initial condition. Each color photograph is approximately 4 square inches. To use the SSPC VIS 5/NACE VIS 9 Guide and Reference Photosgraphs follow these five basic steps. Step 1: Ask, “What does the surface look like prior to surface preparation?” The answer will yield an “Initial Condition” Step 2: Ask, “What level of surface cleanliness does the specification require?” The answer will yield a “Surface Cleanliness Code” Step 3: Ask “How much flash rusting is allowed to remain on the prepared surface?” The answer will yield a “Flash Rust Code” Step 4: Locate the reference photograph in the visual guide illustrating the initial condition (the “answer” to Step 1) and the reference photograph representing the surface wet abrasive blast cleaned to the specified degree of cleanliness (“the “answer” to Step 2) with the specified maximum level of flash rusting permitted, if appropriate (the “answer” to Step 3). Step 5: Use the reference photograph selected in Step 4 to assess whether the prepared steel meets or exceeds the requirements of the specification. Let’s take a closer look at each of these five steps. Protective Coatings Inspector Training ©2015 SSPC
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Step 1: Ask, “What does the steel look like (prior to surface preparation)?” In order to use the visual guide and reference photographs properly, it is important that you determine what the existing steel looks like before it is prepared by wet abrasive blast cleaning. To do this, locate the reference photographs in the visual guide illustrating the two possible initial conditions of the steel. We’ll call these “before photographs,” since they depict the condition of the steel “before” it was wet abrasive blast cleaned. SSPC-VIS 5/NACE VIS 9 depicts only two Initial Conditions, including: Condition C: Steel surface completely covered with rust; little or no pitting visible. Condition D: Steel surface completely covered with rust; pitting visible
Step 2: Ask, “What level of surface cleanliness does the specification require?” After you select a reference photograph that depicts the existing condition of the steel surfaces (the “before photograph”), you’ll need to look at the project specification to determine the degree of surface cleanliness required. The degree of surface cleanliness will appear in the project specification as one of two possible “levels,” including Commercial Blast Cleaning or Near-White Blast Cleaning. If the specification does not require one of these levels of surface cleanliness, an appropriate photograph in the SSPC-VIS 5/NACE VIS 9 Guide and Reference Photographs is not available. Chart 4 provides the surface cleanliness codes and the corresponding levels of surface cleanliness depicted.
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Chart 4 – SSPC-VIS 5/NACE VIS 9 Surface Cleanliness Guide
WAB-6
Surface Cleanliness Level Depicted in Reference Color Photographs Commercial Blast Cleaning
WAB-10
Near-White Blast Cleaning
Surface Cleanliness Code
Write down the surface cleanliness level required by the project specification using the code (e.g., if the specification requires a Commercial Blast using wet abrasive, write down WAB-6). At this point, you should have both a code for the initial condition (C or D) and a code for the surface cleanliness (WAB-6 or WAB-10).
Two initial conditions and two degrees of cleaning for each
Step 3: Ask, “How much flash rusting is allowed to remain on the prepared surface?” After you select a reference photograph that depicts the existing condition of the steel surfaces (the “before photograph”), and determine the degree of surface cleanliness required by the project specification, you will need to determine the amount of flash rusting allowed by the specification. Chart 5 provides the flash rusting codes Protective Coatings Inspector Training ©2015 SSPC
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and the corresponding descriptions. Examples of the appearance of flash rusting are only provided for C WAB-10 and D WAB-6. For other initial conditions and degrees of cleaning, you can use these examples for guidance and make a judgement. Chart 5 - SSPC-VIS 5/NACE VIS 9 Surface Cleanliness Guide Flash Rusting Code L M H
Degree of Flash Rusting Light Medium Heavy
Flash rusting is shown for two initial conditions and two degrees of cleaning
Write down the flash rust code (e.g., if light flash rusting is permitted by the project specification, write down L). At this point, you should have a code for the initial condition (C or D), a code for the surface cleanliness (WAB-6 or WAB-10) and a code for the amount of flash rusting, if permitted (L, M, or H). Step 4: Locate the reference photograph in the visual guide The SSPC-VIS 5/NACE VIS 9 Guide and Reference Photographs illustrates two levels of surface cleanliness (after wet abrasive blast Protective Coatings Inspector Training ©2015 SSPC
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cleaning is completed) for each of the conditions in Step 1. We’ll call these “after photographs.” Select the “after” reference photograph using the code put together in Step 3. Chart 6 contains all of the possible combinations depicted in SSPC VIS 5/NACE VIS 9. Chart 6 – SSPC-VIS 5/NACE VIS 9 Surface Cleanliness Guide Initial Condition
Level of Cleanliness
Flash Rusting
Code
C
Commercial
None
C WAB-6
C
Near-White
None
C WAB-10
C
Near-White
Light
C WAB-10 L
C
Near-White
Medium
C WAB-10 M
C
Near-White
Heavy
C WAB-10 H
D
Commercial
None
D WAB-6
D
Near-White
None
D WAB-10
Example 1: If the steel is rusted but little or no pitting is visible, select Condition C. If the specification requires a Near-White Blast using wet abrasive blast cleaning, select WAB-10. Now locate photograph C WAB-10 in the visual guide.
Example 1: WAB-10 Protective Coatings Inspector Training ©2015 SSPC
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Example 2: If the steel is rusted and pitted, select Condition D. If the specification requires a Commercial Blast using wet abrasive blast cleaning, select WAB-6. If medium flash rusting is permitted, select M. Now locate photograph D WAB-6 M in the visual guide.
Example 2: WAB-6
Step 5: Assess the prepared surfaces Use the reference photograph selected in Step 4 to determine whether the prepared surface(s) meet or exceed the specified level of surface cleanliness. If the prepared surfaces do not meet the specified level of cleanliness, then additional cleaning should be performed and the surfaces re-examined. Document the final surface cleanliness, including the date of the assessment, the visual guide and reference photographs employed, and the area(s) assessed. Also, document whether a project-specific standard was developed and used to help determine specification compliance.
Using SSPC VIS 5/ NACE VIS 9
All surface cleanliness inspection is done with the naked eye or corrected vision. Use of magnification is prohibited by the SSPC surface cleanliness standards. Additionally, some abrasives will embed into steel surfaces. Embedded abrasive is tolerated by the SSPC surface cleanliness standards if they are not water or solvent soluble
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and are tightly adherent. If the embedded abrasive particles cannot be removed by blow down or vacuuming, then they are coated over. If the level of cleaning performed by the contractor is unacceptable, then the deficient areas should be clearly marked and the surfaces reprepared until the specified level of cleaning is achieved. The primer should not be applied until the surfaces are prepared and have been accepted by the inspector. Establishing a Project-Specific Surface Cleanliness Standard/Test Section The images depicted in the SSPC visual guides (both initial condition and after surface preparation) are representative photographs and rarely match the actual conditions before and after surface preparation. Therefore, it is more and more common for specifications to require the contractor to establish a project-specific cleanliness standard (test section, illustrated at left), which is generated by preparing a small, representative section of the structure to the desired level of cleaning. The visual guides are an invaluable tool to help “calibrate” the inspector’s and contractor’s eyes, to help establish the degree of cleaning required by the specification. Once established, this area becomes the visual guide for that project. The agreed-upon condition can be preserved by applying a clear sealer to the surface, or representative 35mm or digital photographs can be taken and used throughout the project. Note that if the existing condition of the structure varies, then more than one test section may need to be generated. Even if the project specification does not require a test section, the inspector may want to ask the contractor to prepare one (or more), so that all parties are on the same page regarding the level of cleanliness required. Centrifugal Blast Cleaning Centrifugal or automated abrasive blast cleaning can be performed using portable or stationary equipment. Portable centrifugal blast machines can be used to prepare floors in warehouse facilities, ship decks and other large, flat surfaces. They can also be mounted to vertical surfaces like the exterior of storage tanks. Stationary equipment is typically located in steel fabrication shops that perform Protective Coatings Inspector Training ©2015 SSPC
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blast cleaning and coating work. In either case, these machines throw or hurl abrasive at the surfaces to be prepared using high-speed centrifugal wheels. The abrasive is automatically loaded onto the wheel vanes through a center hub. Stationary machines are multiwheel, while portable machines generally only have a single wheel.
Centrifugal Blast Cleaning
Like open nozzle abrasive blast cleaning, the degree of surface roughness (depth of the surface profile) is based on the abrasive size employed by the shop. Larger abrasives generate a deeper surface profile than smaller abrasives. The type and size of abrasive may be specified, or the specification may simply indicate the required surface profile depth and the abrasive type and size are left up to the shop performing the work. If a recyclable abrasive is used, the abrasive size may be monitored by performing a sieve analysis. However, it is oftentimes more practical to monitor the surface profile depth generated by the abrasive in use. That is, if the resulting surface profile depth decreases, then the abrasive supply should be augmented with new material, in order to increase the surface profile depth to the specified range. Most centrifugal blast machines were designed to propel steel shot. Many project Centrifugal Blast Cleaning Equipment specifications require an “angular” surface profile to be generated, which is not possible with steel shot. To resolve this issue, fabrication shops oftentimes elect to use an operating blend or mix of steel shot and steel grit to blast clean the steel. The inspector may be required to verify that the mix of abrasive shapes is producing the angular surface profile required by the specification. This is typically a visual inspection. Alternatively, a peak count measurement can be obtained, as a surface with an angular profile will have a higher peak count than a surface prepared with steel shot. Note that the contract must indicate the specified peak count range, otherwise the shop can not be held responsible for conformance to a specific peak density. In addition, the operator and inspector will typically monitor the abrasive supply in the machine for contamination by oil using the “vial test.”
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Vacuum Blast Cleaning Vacuum blast cleaning is similar to dry abrasive blast cleaning, except that the blast nozzle is equipped with a Neoprene rubber & bristle brush shroud (collar) that is held tightly against the surface rather than 46-60 cm (18-24 inches) away. In this manner, the abrasive impacts the surface and is immediately vacuumed off, together with the materials removed from the surface. The debris is separated from the abrasive and the abrasive is reused. Vacuum abrasive blast cleaning is used when a high degree of cleanliness and a surface roughness are required, but airborne abrasive and dust cannot be tolerated. Surface irregularities can cause the vacuum shroud to lose contact with the surface and result in releases to the environment. Also, Vacuum Blast Cleaning vacuum blast cleaning is slow, so it is often limited to preparing small areas. Conducting a Compressed Air Cleanliness (blotter) Test As we discussed earlier in this module, compressed air is used to propel abrasive through a blast hose and out the end of a blast nozzle. It is this compressed air volume and pressure that gives velocity to the abrasive and cleans and roughens the surfaces. However, if the air being generated by the compressor contains oil or water, then the abrasive and the surface can become contaminated. It is not unusual for compressed air to contain water and/or oil. As a result, the compressed air must be filtered and/or dried before it comes in contact with the abrasive. Oil and water separators, desiccant air driers or air coolers are very effective at cleaning and/or drying the compressed air provided that they are both operational and properly maintained. From the perspective of the inspector, it is not enough to ensure operation and maintenance of this equipment. Rather the inspector must verify that the air is clean and dry. ASTM D4285, “Test Method for Indicating Oil or Water in Compressed Air” describes a standard practice for verifying the cleanliness of compressed air. It is perhaps better known as a “blotter test.” Briefly, clean white absorbent cloth or white blotter paper Compressed Air Blotter Test is attached to a rigid frame and the compressed Protective Coatings Inspector Training ©2015 SSPC
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air is exhausted on to the cloth or paper (down stream of compressed air drying/filtration equipment) at a distance of approximately 18” for approximately one minute. For large volumes of air, the blotter paper or cloth may be replaced with thick, rigid Plexiglas. After the test is complete, the cloth, blotter paper or Plexiglas is visually examined for oil or water. Any visible amount is cause for rejection. It is the responsibility of the contractor to maintain or replace equipment until a satisfactory air supply is achieved. The date, time of day and test result (pass/fail) is documented. Compressed air cleanliness is an indirect requirement of the SSPC surface cleanliness standards for abrasive blast cleaning. Blast Nozzles Blast nozzles range in both type and size (length and inside diameter). Some blast nozzles are designed such that the abrasive exits through the side rather than the front, enabling the operator to clean even very tightly configured areas, like the backside of angles, etc. In general, there are two basic designs: straight-bore and venturi. Straight bore nozzles are generally less productive than the venturi design. The venturi shape increases the velocity of the abrasive, so that as it exits the nozzle it is traveling at a higher speed. However, both nozzle designs can produce the desired degree of cleanliness and surface profile depth. Shorter venturi nozzles are generally less productive than longer venturi nozzles, as the abrasive speed does not increase dramatically. However, a shorter blast nozzle may afford the operator better access to Blast Nozzles hard-to-reach or tightly configured areas. The lining of a blast nozzle can be manufactured from boron carbide, silicon carbide, tungsten carbide, even ceramic. While these lining materials are very resilient to wear, they are very brittle and can crack if the nozzle is handled improperly. All blast nozzles are sized in 1.6 mm (1/16 inch), which represents the inside diameter of the nozzle. For example, a No. 7 blast nozzle has an inside orifice diameter of 11 mm (7/16”) when it is new. As abrasive passes through the nozzle, the lining will wear, enlarging the orifice and opening the venturi, making it less productive over time. Nozzle wear can be monitored using a pressure blast analyzer gage (nozzle orifice gage). Briefly, the
Nozzle Orifice Gage
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conical-shaped gage is first marked using a black china marker, then inserted into the threaded end of the blast nozzle as far as it will go, twisted and withdrawn. The nozzle opening will etch the black china marking, which coincides with a demarcation on the gage face (increments of 1/16” or 1.5 mm). According to SSPC’s abrasive blast cleaning training program (C7), blast nozzles should be replaced when the opening increases by one size (e.g., a No. 6 blast nozzle measures Straight and Venturi Nozzles 8/16” [13mm] on the nozzle orifice gage). Abrasives There are a variety of abrasives that can be used in the blast cleaning process. They fall into two broad categories: expendable and recyclable. Expendable abrasives are typically used once then discarded, since the “breakdown rate” is relatively high. Conversely, the breakdown rate of recyclable abrasives is relatively low, allowing them to be used multiple times, before they are discarded. For example, a recyclable steel grit abrasive can be reused over 100 times with minimal breakdown. However, even the recyclable abrasive supply is routinely augmented with fresh media, in order to maintain the abrasive quantity required for operation of the system (the smaller particles are typically drawn off by the ventilation system) and to maintain the specified surface profile depth. Expendable Abrasives Expendable abrasives fall into two general categories: Mineral and Slag. Mineral abrasives are naturally occurring and include silica sand, garnet, and staurolite sand (StarBlast®). Note that garnet can be reused a couple of times, provided that nozzle pressures are maintained below optimum i.e., 517-552 KPa (75-80 psi). Slag abrasives are not naturally generated, but rather represent byproducts of other industries,
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which are processed into abrasives. These include copper, coal and nickel slag. Corncobs and walnut shells are also naturally occurring and can be used as polishing abrasives. However these abrasives are not aggressive enough to remove industrial protective coatings and are not hard enough to generate a surface profile into steel. SSPC Abrasive Specification No. 1 (AB 1), “Mineral and Slag Abrasives” defines the requirements for selecting and evaluating mineral and by-product and manufactured abrasives used for blast cleaning. SSPC-AB 1 categorizes expendable abrasives by “Type, Class and Grade,” depending on the general type, the crystalline silica content and surface profile that the abrasive will yield. The two Types, three Classes and five Grades are listed below: Type I: Natural Mineral Abrasives Type II: By-Product and Manufactured Abrasives Class A: < 1% Crystalline Silica Class B: < 5% Crystalline Silica Class C: Unrestricted Crystalline Silica Grade 1: Surface profile yield of 13-38 µm (0.5-1.5 mil) Grade 2: Surface profile yield of 25-64 µm (1.0-2.5 mils) Grade 3: Surface profile yield of 51-89 µm (2.0-3.5 mils) Grade 4: Surface profile yield of 75-127 µm (3.0-5.0 mils) Grade 5: Surface profile yield of 102-150 µm (4.0-6.0 mils) SSPC-AB 1 contains a list of tests that the abrasive manufacturer must conduct and report on prior to publishing that the abrasive meets the standard. Some of these tests can be performed by the inspector in the field (on a lot basis), while some can only be performed in a testing facility. If the project specification requires the abrasive to meet SSPC-AB 1, then the inspector should require a copy of the test report from the abrasive supplier and may conduct some field testing to verify conformance to AB 1. Following is a list of tests required in order to categorize an abrasive as meeting SSPC-AB 1. An * indicates that the inspector can also perform this test in the field to verify that the lot of abrasive delivered to the site meets the requirements of SSPC-AB 1. Note that the abrasive cleanliness requirements listed in SSPC-AB 1 are indirect requirements of the SSPC abrasive blast cleaning standards when an expendable abrasive is used. This is explained in greater detail later. Protective Coatings Inspector Training ©2015 SSPC
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Specific Gravity Hardness Weight change on ignition Water soluble contaminants* Moisture content Oil content* Crystalline Silica content Surface profile yield* Particle size distribution (sieve analysis)* Recyclable Abrasives Recyclable abrasives generally include steel grit, steel shot and aluminum oxide. Steel grit and aluminum oxide (as well as all of the expendable media listed above) are considered “angular,” which means they contain sharp points that in turn produce sharp peaks and valleys in the surface. This equates to an increase in the surface area of the steel, due to the density of the peak pattern (peaks are close together and there are many of them). Conversely, steel shot is considered a round or spherical abrasive that produces a rounded profile or a “peened” surface texture. This results in a comparatively lower peak density pattern, because the peaks are round, further apart and there are less of them. Some coating systems (like thermal spray coatings) rely heavily on a mechanical bond to the surface. They cannot tolerate a peened surface texture, and can disbond independent of the surface profile depth. However, most liquidapplied coatings adhere sufficiently to both angular and rounded surface profile patterns. SSPC Abrasive Specification No. 3 (AB 3), “Newly Manufactured or Re-Manufactured Steel Abrasives” defines the requirements for steel abrasives used for blast cleaning, and SSPC Abrasive Specification No. 2 (AB 2), “Cleanliness of Recycled Ferrous Metallic Abrasives” defines the cleanliness requirements for Steel Grit recycled blast cleaning abrasive. The abrasive cleanliness requirements referenced in both abrasive specifications are indirect requirements of the SSPC abrasive blast cleaning standards.
Steel Shot
Protective Coatings Inspector Training ©2015 SSPC
Similar to SSPC-AB 1, SSPC-AB 3 (Ferrous Metallic Abrasive) contains a list of tests that the abrasive manufacturer must conduct and report on prior to publishing that the abrasive meets the standard. Some of these tests can be performed by the inspector in the field (on a lot basis), while some can only be performed in a testing facility. If the project 3-80
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specification requires the abrasive to meet SSPC-AB 3, then the inspector should require a copy of the test report from the abrasive supplier and may conduct some field testing to verify conformance to AB 3. Following is a list of tests required in order to categorize an abrasive as meeting SSPC AB 3. An * indicates that the inspector can also perform this test in the field to verify that the lot of abrasive delivered to the site meets the requirements of SSPC-AB 3. Class (Class 1 is steel abrasive and Class 2 is iron abrasive) Abrasive size* Specific Gravity Chemical composition Hardness Durability Cleanliness* Conductivity*
Angular Abrasive Measuring Sieves
SSPC-AB 2 (Cleanliness of Recycled Ferrous Metallic Abrasive) is different than either of the two abrasive specifications described previously. While SSPC-AB 2 governs steel and other “recyclable” abrasives, it specifies the cleanliness of used or recycled abrasive (not new abrasive). Therefore the abrasive manufacturer does not test the abrasive nor prepare a test report for conformance to AB 2. Rather, the abrasive is tested in the field and/or in a laboratory. A list of the tests required by SSPC-AB 2 is provided below. The testing requires specific supplies and test equipment. Therefore, as an inspector, if you are required to perform testing (or oversee testing performed by the contractor’s quality control personnel) to determine conformance of the recycled abrasive to AB 2 in the field (denoted by an *), then you should carefully read the procedures described in SSPC-AB 2. Non-abrasive residue* Lead content (laboratory only) Water soluble contaminants* Oil content* SSPC-AB 4 (Recycled Encapsulated Abrasive Media) defines performance requirements for recyclable encapsulated abrasive media consisting of steel grit or aluminum oxide in a compressible open-cell matrix (i.e., “sponge”). It requires specialized equipment and is used when dust control is a priority.
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Abrasive Size Round abrasives (like steel shot) are sized based on the diameter of the shot. For example an S330 shot is 0.33mm in diameter and an S230 shot is 0.23mm in diameter. Therefore, the larger the shot number, the larger the abrasive size. Angular abrasives are sized differently than shot. These abrasives are sized according to sieve number. Each sieve contains a fine mesh screen containing square openings. The sieves are identified according to the number of openings in the mesh, per linear inch of screen. For example, a Tyler No. 20 sieve has 20 openings per linear inch of screen, while a No. 60 sieve has 60 openings per linear inch of screen. Naturally, these openings must be considerably smaller in order to fit three times the number of openings into the same area. Therefore, with angular abrasives the larger the number is, the smaller the abrasive size. For example, a No. 12 abrasive is larger than a No. 40. Sometimes abrasives are “pre-blended” by the manufacturer into two sizes. For example, Black Beauty® 1240 is a blend of particle size 12 and particle size 40 in a single bag or lot. The larger-sized particles fracture the rust and old coating and generate the surface profile depth, while the smaller particles “scour” the surface to the desired level of cleaning. Abrasive Cleanliness The contractor and the inspector may be required to monitor the abrasive supply for contamination by oil per ASTM D7393 Standard Practice for Indicating Oil in Abrasives or soluble salts. This is commonly referred to as a “vial test.” To conduct a vial test for oil, place a sample of the abrasive in a clean container to about half of its height. Add water to a level at least 2.5 cm (1 in.) above the top of the abrasive. The water temperature shall be between 20 and 30oC (68 and 95oF). Cover the container and shake vigourously for one min. Remove the cover from the container and let it sit for 5 min. Examine the surface of the water for oil droplets or oil sheen. If oil is detected, retest after cleaning abrasive. If the project specification requires an abrasive test for conductivity (soluble salt contamination), then the procedure prescribed in ASTM D4940, “Standard Test Method for Conductimetric Analysis of Water Soluble Ionic Contamination of Blasting Abrasives” should be Protective Coatings Inspector Training ©2015 SSPC
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used. If the project specification references SSPC-AB 1, AB 2, AB 3 or AB 4 the tolerable threshold for conductivity is 1,000 microsiemen. Note that the conductivity of the water used for the extraction should be tested for conductivity and this value (the “blank”) subtracted from the test value. Measuring Surface Profile Depth Surface profile is defined as the maximum peak-to-valley depth that is generated by abrasive impacting the surface at high speed and by the impact created using certain power tools. By imparting a profile, the surface area is increased, enhancing the adhesion of the coating system to the surface. While an insufficient surface profile depth may result in poor coating system adhesion, excessive surface profile may cause pinpoint rusting and will require significantly more coating to fill all of the “valleys” of the surface profile and provide the specified thickness of coating above the “peaks” of the surface profile. Therefore, compliance with the minimum and maximum specified surface profile depth is critical to the success of a coating system. Factors affecting the depth of the surface profile were discussed earlier in this module, and included (for abrasive blast cleaning) the type, hardness and size of the abrasive media employed, as well as the hardness of the surface being prepared. Lesser factors include the distance from the blast nozzle to the surface and the angle at which the operator holds the nozzle to the surface. For power tool cleaning, the type of tool and the configuration of the “impactors” will oftentimes dictate the depth of the surface profile. Adjusting to changes in profile depth requirements in specifications is best achieved by selecting a different sized abrasive. For projects requiring a relatively shallow surface profile depth, a smaller abrasive should be selected. For projects requiring a relatively deep surface profile, a larger abrasive should be selected, but may be blended with a smaller abrasive to increase productivity. JPCL (Vol. 22, No. 6 and Vol. 23, No. 6) has published articles that describe the importance of other surface roughness attributes, in addition to average peak-to-valley distance, including peak count (Pc), maximum roughness depth (Rmax) and maximum profile height (Rt). Based on laboratory research conducted by Roper, et. al., and published in JPCL as listed above, increased peak density improves Protective Coatings Inspector Training ©2015 SSPC
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coating adhesion and reduces corrosion undercutting beneath a coating system damaged while in service compared to surfaces with correspondingly lower peak counts. Methods of generating various peak densities are described in the articles, and are based on abrasive size, shape, hardness and other factors. Because of the industry’s recognition of the importance of surface roughness characteristics (beyond average surface profile depth), ASTM D7127, “Standard Test Method for Measurement of Surface Roughness of Abrasive Blast Cleaned Metal Surfaces Using a Portable Stylus Instrument” was published in 2005. The standard describes the procedures for verifying accuracy and using portable stylus-type instruments to obtain surface characterization data. An inspector may be required to perform peak count measurements in addition to peakto-valley depth measurements (if required by the project specification). There are three industry-recognized standards for measuring surface profile, including ASTM D4417, “Test Methods for Field Measurement of Surface Profile of Blast Cleaned Steel,” NACE SP0287, “Field Measurement of Surface Profile of Abrasive Blast Cleaned Steel Surfaces Using a Replica Tape,” and ASTM D7127 “Standard Test Method for Measurement of Surface Roughness of Abrasive Blast Cleaned Metal Surfaces Using a Portable Stylus Instrument.” These methods prescribe how to obtain measurements of surface profile depth and peak count, but do not provide an acceptance criterion (e.g., “the surface profile shall be 50-88 µm [2-3.5 mils…”]). Therefore, the project specification must indicate the desired surface profile depth and the minimum peak count (as required). ASTM D4417 describes three methods for field measurement of surface profile depth (Methods A, B, and C), while NACE SP0287 describes only one method (the same as Method C in ASTM D4417). Therefore, we will be focusing on the ASTM standard rather than the NACE recommended practice. The step-by-step procedures for use of surface profile measuring instruments are described below. Profile conformance is determined by following SSPC-PA 17.
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Using the Surface Profile Comparator ISO 8503-1/2 and Method A of the ASTM standard for measurement of surface profile after abrasive blast cleaning describes the use of surface profile comparators. For this method, you visually compare the prepared steel surface to a disc or coupon containing known anchor patterns. The Surface Profile Comparator employs a 5 power illuminated magnifier and one comparator disc. The sequence of steps on how to read profile using a surface profile comparator can be found in the instrument supplement at the end of this module.
Using the Surface Profile Depth Gage Method B of the ASTM standard for measurement of surface profile after abrasive blast cleaning describes the use of a surface profile depth micrometer. The Surface Profile Depth Gage is suited for this method of measurement. It is also the method specified for surface profile when the steel substrate has been cleaned by hand and power tools. For this method, you measure the depth of the “valleys” using a cone-shaped metal tip. The surface profile depth is indicated on the gage dial or on the digital display, depending on the model you choose. For step-by-step instructions on how to take surface profile Surface profile depth micrometers readings using a surface profile depth gauge, refer to the instrument supplement at the end of this module.
Using Replica Tape Method C of the ASTM standard for measurement of surface profile after abrasive blast cleaning describes the use of a replica tape in conjunction with a spring-loaded micrometer. Testex® is the manufacturer of the replica tape. Testex® also private-labels the Mitutoyo spring micrometer. This method of surface profile measurement entails generating an “impression” of the anchor pattern, then measuring the impression using a spring-loaded micrometer. This Protective Coatings Inspector Training ©2015 SSPC
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method is the most repeatable and reproducible of the three methods described in the standard.
Replica tape, spring micrometer and burnishing tool
The replica tape itself consists of a non-compressible 50 µm (2 mil) film of Mylar® and a compressible layer of foam, which is attached to the underside of the Mylar (see Figure 1). While the Mylar remains a constant 50 µm (2 mils), the amount of compressible foam varies depending on the range of the replica tape. This compressible foam is pressed into the anchor pattern created during abrasive blast cleaning, effectively creating a mirror image of the surface profile in the foam. This peak-to-valley impression is then measured using a calibrated spring micrometer.
Figure 1
Calibrating Surface Profile Measuring Instruments Calibration of the Surface Profile Comparator is not required. However, if the comparator discs become tarnished, they can be difficult to use. A soft pencil eraser can be used to remove the tarnish without disturbing the electroformed pattern on each segment. Protective Coatings Inspector Training ©2015 SSPC
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Calibration of the Surface Profile depth micrometer was described earlier. This “zero set” adjustment procedure should be conducted prior to and after each period of use. While the replica tape itself does not require calibration, the micrometer should be verified for accuracy routinely by inserting shims of known thickness into the micrometer and verifying a correct measurement. Plastic shims used to verify the accuracy of coating thickness gages can be used for this purpose. However, it should be recognized that these shims may not represent an exact thickness.
Documenting Surface Profile Measurements Documentation of the surface profile measurements includes the date of measurement, the method employed (ASTM D4417, Method A, B or C), the area(s) of measurement, the number of measurements obtained, and the range and average of the measurements taken. This can be formatted as shown. Date
5/13/02
6/3/02
6/5/02
Measurement Method Employed (D4417)
C (X-coarse)
C (X-coarse)
A (G/S disc)
Item Measured
Beam 4-1
Beam 4-2
Plate 6-1
Number of Measurements
3
3
5
Surface Profile Range
63-73 µm (2.5-2.9 mils)
58-70 µm (2.3-2.8 mils)
50-75 µm (2-3 mils)
Surface Profile Average
68 µm (2.7 mils)
63 µm (2.5 mils)
50-75 µm (2-3 mils)
1
1A:
Surface Profile Comparator
Using Portable Stylus Instruments for Determining Peak Density There are several types of portable stylus instruments that can be used to measure peak density. Each device operates somewhat differently but they all require the user to position a retractable arm containing a diamond point stylus (typically 5μm in diameter). The arm containing the stylus is connected to a data collection device. The arm is automatically retracted by the data logger at a constant speed
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across a known length of the prepared surface (typically 5.6 mm). The total length that the arm travels is divided into seven equal segments. Segments 1 and 7 are used in the calibration verification phase, while segments 2 through 6 are used by the data logger to compute peak count, as well as other parameters, if desired. The number of peaks per linear segment is revealed by the instrument display. A minimum of five traces should be measured and averaged to generate a single representative peak count for a given area. Frequency of Surface Profile Measurements The number of surface profile measurements to make may be stipulated by the project specification. If not, the inspector will need to use some judgment as to the frequency of measurements. Difficult access areas as well of the number of blast operators should be considered. According to ASTM D4417, for each area selected, a minimum of three readings is required and the average and range of the surface profile recorded.
Stylus type device
Close-up of stylus on blast cleaned surfaces
SSPC-PA 17 describes a procedure suitable for shop or field use for determining compliance with specified profile ranges on a steel substrate using Methods A (visual comparator), B (depth micrometer) and C (replica tape) as described in ASTM D4417, and the portable stylus instrument method used to determine surface roughness and peak count as described in ASTM D7127. The standard sets requirements for evaluating the preparation process, obtaining surface profile readings, obtaining surface roughness and peak count read¬ings, and determining if the profile of an evaluated area is within the specified range. For each specific surface preparation apparatus used during each work shift or twelve-hour period, whichever is Protective Coatings Inspector Training ©2015 SSPC
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shorter, you are required to select a minimum of three 15 x 15 cm (or three 6 x 6 inch) locations in which to take readings. The standard defines “apparatus” as an individual blast pot (which may supply multiple nozzles), individual self-contained abrasive recycling/blast cleaning units (which may contain multiple pots), individual stationary or mobile centrifugal cleaning unit, or individual power tool. The number of read¬ings to determine the average profile at each location on steel substrates is based on the number required by ASTM D4417 or, if the portable stylus instrument is specified, the number required by ASTM D7127. The average of the readings at each location shall be the “location average.” Waterjetting Surface preparation by waterjetting under various water pressures can remove even tightly-adhering coating systems from the underlying surfaces. Waterjetting (at any pressure) will not generate a surface profile; however at higher pressures, waterjetting can restore an existing surface profile. If a surface profile is required by the project specification (but does not pre-exist), then alternative methods of surface preparation may be employed, in addition to coating and rust removal by waterjetting. Wet abrasive blast cleaning (with abrasive injection) can be used in this capacity. The levels of waterjetting pressure are: LPWC: Low Pressure Water Cleaning up to 35 MPa (5,000 psi) HPWC: High Pressure Water Cleaning 35-69 MPa (5,000-10,000 psi) HPWJ: High Pressure Waterjetting 69-207 MPa (10,000-30,000 psi) UHPWJ: Ultra-High Pressure Waterjetting >207 MPa (30,000 psi)
Water Cleaning/Jetting
Selecting the water pressure to employ is dependent on the adhesion of the existing coating to the surface and the desired level of cleanliness. Surface rusting can be removed using waterjetting, but intact mill scale cannot, and will require mechanical removal or selection of a coating system that can be applied to intact mill scale and still perform adequately in the service environment. Low pressure water cleaning (LPWC) or “pressure washing” is often specified for overcoating projects, where the existing coating is salvageable and is incorporated into the maintenance coating system for the structure. LPWC can be very effective in removing dirt,
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chalking, bird droppings and other contaminants from the surfaces, although mechanical agitation of the surface during LPWC is often required to ensure adequate removal. The remaining three levels of water jetting pressure are used primarily to remove coatings. Waste generation is minimized, in that the water is captured, filtered and reused. The debris that is created is limited to the materials removed from the surface. This is particularly advantageous when the coating to be removed contains toxic metals, as the cost of handling, transporting and disposing of hazardous waste can be relatively high. Like most coating removal operations, water jetting has inherent worker hazards. Personal protective equipment, including (but not limited to) special foot, leg, arm, hand and torso guards are often required when water jetting operations are employed, since using water under these high pressures is essentially a lance and can cut or even dismember an operator or adjacent worker.
SSPC/NACE Joint Surface Preparation Standards Waterjet Cleaning of Metals The four SSPC/NACE waterjet cleaning of metals standards require the specifier to communicate to the contractor the level of surface cleanliness desired (4 options), and the degree of flash rusting that will be tolerated (4 options). The standard also provides the user with guidance on specifying the level of non-visible surface contaminants that will be tolerated. The four levels of surface cleanliness are: SSPC-WJ-1/NACE WJ 1:Clean to Bare Substrate: A metal surface after Clean to Bare Substrate, when viewed without magnification, shall have a matte (dull, mottled) finish and shall be free of all visible oil, grease, dirt, rust and other corrosion products, previous coatings, mill scale, and foreign matter. Thin films of mill scale, rust and other corrosion products, and coating are not allowed. The gray to brownblack discoloration remaining on corroded and pitted carbon steel that cannot be removed by further waterjet cleaning is allowed. SSPC-WJ-2/NACE WJ 2 Very Thorough or Substantial Cleaning: A metal surface after Very Thorough Cleaning, when viewed without magnification, shall have a matte (dull, mottled) finish and shall be free of all visible oil, grease, dirt, rust, and other corrosion products except for randomly dispersed stains of rust and other corrosion products, tightly adherent thin coatings, and other tightly adherent foreign matter. The staining or tightly adherent matter shall be limited Protective Coatings Inspector Training ©2015 SSPC
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to no more than 5 percent of each unit area of surface and may consist of randomly dispersed stains of rust and other corrosion products or previously applied coating, tightly adherent thin coatings, and other tightly adherent foreign matter. SSPC-WJ-3/NACE WJ 3: Thorough Cleaning: A metal surface after Thorough Cleaning, when viewed without magnification, shall have a matte (dull, mottled) finish and shall be free of all visible oil, grease, dirt, rust, and other corrosion products except for randomly dispersed stains of rust and other corrosion products, tightly adherent thin coatings, and other tightly adherent foreign matter. The staining or tightly adherent matter shall be limited to no more than 33 percent of each unit area of surface and may consist of randomly dispersed stains of rust and other corrosion products or previously applied coating, tightly adherent thin coatings, and other tightly adherent foreign matter. SSPC-WJ-4/NACE WJ 4 Light Cleaning: A metal surface after Light Cleaning, when viewed without magnification, shall be free of all visible oil, grease, dirt, dust, loose mill scale, loose rust and other corrosion products, and loose coating. Any residual material shall be tightly adhered to the metal substrate and may consist of randomly dispersed stains of rust and other corrosion products or previously applied coating, tightly adherent thin coatings, and other tightly adherent foreign matter. Coatings, mill scale, and foreign matter are considered tightly adherent if they cannot be removed by lifting with a dull putty knife. The gray to brown-black discoloration remaining on corroded and pitted carbon steel that cannot be removed by further waterjet cleaning is allowed. Similar to wet abrasive blast cleaning, the water used in waterjetting is going to cause carbon steel surfaces to flash rust. Therefore, the specifier may require the use of a rust inhibitor (that is compatible with the coating system to be applied to the prepared surfaces), or simply accept the flash rusting that occurs and select a coating system that is tolerant in the given environment. The SSPC visual guides and reference photographss (discussed later in this module) for water jetting illustrate the levels of flash rusting (light, medium and heavy), so that the degree of tolerable surface rust can be judged by the inspector. When mutually agreed upon or when invoked by the contract documents, SSPC VIS 4/NACE VIS 7 photographic references can Protective Coatings Inspector Training ©2015 SSPC
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be used to help evaluate the cleanliness of surfaces prepared by waterjetting. SSPC VIS 5/NACE VIS 9 photographic references can be used to help evaluate the cleanliness of surfaces prepared by wet abrasive blast cleaning. While the photographic references in these visual guides will rarely match the actual surfaces prepared by the contractor, they serve as an excellent tool to help those evaluating the degree of cleanliness achieved to “calibrate” their eyes, and they are invaluable for establishing a jobsite cleanliness standard. The use of these visual guides is described later in this module. Other SSPC Surface Preparation Standards Two standards not otherwise categorized include SSPC-SP8, “Pickling” and SSPC-SP13/NACE No. 6, “Surface Preparation of Concrete.”
Using SSPC-VIS 4 /NACE VIS 7, “Guide and Reference Photographs for Steel Surfaces Prepared by Waterjetting” SSPC-VIS 4/NACE VIS 7 is a collection of color reference photographs depicting six initial conditions and four levels of cleaning by waterjetting for each condition. Most of the color reference photographs are approximately 9 square inches, but some are 4 square inches. To use the SSPC VIS 4/NACE VIS 7 Guide and Reference Photographs, follow these five basic steps. Step 1: Ask, “What does the steel look like prior to surface preparation?” The answer will yield an “Initial Condition” Step 2: Ask, “What level of surface cleanliness does the specification require?” The answer will yield a “Surface Cleanliness Code”
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Step 3: Ask, “How much flash rusting is allowed to remain on the prepared surface?” The answer will yield a “Flash Rust Code” Step 4: Locate the reference photograph in the visual guide illustrating the initial condition (the “answer” to Step 1) and the reference photograph representing the specified degree of surface cleanliness by waterjetting (the “answer” to Step 2) with the specified maximum level of flash rusting permitted (the “answer” to Step 3, if appropriate). Step 5: Use the reference photograph selected in Step 4 to assess whether the prepared steel meets or exceeds the requirements of the specification. Let’s take a closer look at each of these five steps. Step 1: Ask, “What does the steel look like (prior to surface preparation)?” In order to use the visual guide and reference photographs properly, it is important that you determine what the existing steel looks like before it is prepared by waterjetting. To do this, locate the reference photographs in the visual guide illustrating the six possible initial conditions of the steel. We’ll call these “before photographs,” since they depict the condition of the steel “before” it was cleaned by waterjetting. SSPC-VIS 4/NACE VIS 7 depicts six Initial Conditions, including: Condition C: Steel surface completely covered with rust; little or no pitting visible . Condition D: Steel surface completely covered with rust; pitting visible.
Condition E: Previously painted steel surface; mostly intact, lightcolored paint applied to a blast cleaned surface. Protective Coatings Inspector Training ©2015 SSPC
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Condition F: Previously painted steel surface; mostly intact, zinc-rich paint applied to a blast cleaned surface.
Condition G: Paint system applied to mill scale bearing steel; system thoroughly weathered, blistered or stained. Condition H: Degraded paint system applied to steel; system thoroughly weathered, blistered or stained.
Select one of these “before” reference photographs that best illustrates the condition of the steel and write down the letter (C, D, E, F, G or H) before you proceed to Step 2. I f the steel is represented by more than one condition, then write down the specific area of the structure and the corresponding condition letter for each area. Step 2: Ask, “What level of surface cleanliness does the specification require?” After you select a reference photograph that depicts the existing condition of the steel surfaces (the “before photograph”), you’ll need to look at the project specification to determine the degree of surface cleanliness required. The degree of surface cleanliness will appear in the project specification as one of four possible “levels,” including WJ4, Light Cleaning; WJ-3, Thorough Cleaning; WJ-2, Very Thorough Cleaning; or WJ-1, Clean to Bare Substrate. If the specification does not require one or more of these levels of surface cleanliness, then the SSPC-VIS 4/NACE VIS 7 Guide and Reference Photographs cannot be used. Chart 7 provides the surface cleanliness codes and the corresponding levels of surface cleanliness depicted. Protective Coatings Inspector Training ©2015 SSPC
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Chart 7 - SSPC VIS 4/NACE VIS 7 Surface Cleanliness Guide Surface Cleanliness Code WJ-4 WJ-3 WJ-2 WJ-1
Surface Cleanliness Level Depicts in Reference Color Photographs Light Cleaning Thorough Cleaning Very Thorough Cleaning Clean to Bard Substrate
Write down the surface cleanliness level required by the project specification using the code (e.g., if the specification requires very thorough cleaning, write down WJ-2). At this point, you should have both a code for the initial condition (C, D, E, F, G or H) and a code for the surface cleanliness (WJ-1, WJ-2, WJ-3 or WJ-4). Step 3: Ask, “How much flash rusting is allowed to remain on the prepared surface?” After you select a reference photograph that depicts the existing condition of the steel surfaces (the “before photograph”), and determine the degree of surface cleanliness required by the project specification, you will need to determine the amount of flash rusting permitted by the specification. Note: Photographs of flash rusting are only provided when the initial condition of the surface was rusted (Condition C) or rusted and pitted (Condition D), and for Thorough Cleaning (WJ-3) or Very Thorough Cleaning (WJ-2), but the appearance can be applied to other conditions (e.g., WJ-3 used on previously, painted steel). Chart 8 provides the flash rusting codes and the corresponding descriptions. Write down the flash rust code (e.g., if medium flash rusting is permitted by the project specification, write down M). At this point, you should have a code for the initial condition (C, D, E, F, G or H), a code for the surface cleanliness (WJ-1, WJ-2, WJ-3 or WJ-4) and a code for the amount of flash rusting permitted (L, M or H).
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Chart 8 – SSPC-VIS 4/NACE VIS 7 Surface Cleanliness Guide Flash Rusting Code
Degree of Flash Rusting
L M H
Light Medium Heavy
REMEMBER: The flash rusting photographs are only provided if the initial condition of the surface was “C” or “D,” and the project specification requires either “WJ-3” or “WJ-2” cleaning, but the appearance can be applied to other conditions. Condition G selected
Step 4: Locate the reference photograph in the visual guide The SSPC-VIS 4/NACE VIS 7 Guide and Reference Photographs illustrates four levels of surface cleanliness (after waterjetting is completed) for each of the conditions in Step 1. We’ll call these “after photographs.” Select the “after” reference photograph in the visual guide using the code put together in Step 3. Here are two examples:
G WJ-2 selected
Example 1: If the steel contains mill scale and a paint system that is thoroughly weathered, select Condition G. If the specification requires very thorough waterjetting, select WJ-2. Now locate photograph G WJ‑2 in the visual guide and reference photographs. Example 2: If the steel surface is rusted and pitted, select Condition D. If the specification requires thorough waterjetting, select WJ3. If medium flash rusting is permitted, select M. Now locate photograph D WJ-3 M in the visual guide and reference photographs.
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Condition D selected (Initial Condition)
D WJ-3 selected for level of cleanliness
D WJ-3 selected since medium flash rust allowed
Step 5: Assess the prepared surfaces. Use the reference photograph selected in Step 4 to determine whether the prepared surface(s) meet or exceed the specified level of surface cleanliness. If the prepared surfaces do not meet the specified level of cleanliness, then additional cleaning should be performed and the surfaces re-examined.
Using SSPC-VIS 4/ NACE VIS 7
Remember: Ambient lighting and variations in the initial condition, as well as the quality of the steel will impact the appearance of the prepared surface and the perceived level of cleanliness. Also, unless rust inhibitors are used in the water, the prepared surfaces will flash rust, independent of whether the specification addresses permissible quantities of rust-back (light, medium or heavy) and whether the visual guide illustrates this condition. Since cleanliness assessments can be subjective, it may be worthwhile to establish a projectspecific cleanliness standard (using the visual guides and reference photographss for guidance) before a job begins. This can help all parties involved gain a mutual understanding of the desired level of cleanliness. The SSPC visual guides and reference photographss were designed as a guide, and the written standards prevail in the event of a dispute.
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Recommended Guidelines for Evaluating Flash Rust This is a non-mandatory guide with text and reference photographs describing how to perform a field assessment of the amount of flash rust on a steel surface by brushing the surface with a paint brush wrapped with a white cotton cloth and evaluating the color and amount of rust that transfers to the cloth. The guide was developed for the National Shipbuilding Research Program Surface Preparation and Coatings Panel (NSRP SP-3). To evaluate flash rust perform the “Wipe” test. To conduct this test perform the following steps: 1. Use a white, lint-free, woven cotton cloth and a standard 4-inch nylon bristle paint brush. 2. Neatly wrap cloth around the paint brush. Hold the cloth in such a manner as to prevent it from slipping. 3. Swipe the cloth across the surface in one motion, using the amount of pressure you would use when applying house paint to a door. 4. The length of the swipe should be consistent. The NSRP Guide recommends one pass at 6 inches (15 cm). 5. Evaluate the amount of rust transferred to the cloth. ISO F1: Flame Cleaning “When viewed without magnification, the surface shall be free from mill scale, rust, paint coatings and foreign matter. Any remaining residues shall show only as a discoloration of the surface (shades of different colours.)” SSPC-SP 8, Pickling SSPC-SP 8, “Pickling” is a pretreatment process for steel surfaces prior to hot-dip galvanizing. The pickling bath may contain sulfuric or hydrochloric acid and is designed to remove grease, oil, mill scale, rust and other debris from steel surfaces. SSPC-SP 16, Brush-Off Blast Cleaning of Galvanized Steel, Stainless and Non-Ferrous Metals This standard covers surface preparation of coated or uncoated metal surfaces other than carbon steel prior to the application of a protective Protective Coatings Inspector Training ©2015 SSPC
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coating system. Surface preparation using this standard is intended to roughen and clean a non-ferrous metal substrate. Substrates that may be prepared by this method include, but are not limited to, galvanized surfaces, stainless steel, copper, aluminum, brass, as well as intact coatings over these substrates. Chemical Stripping Removal of coatings using chemical strippers has been widely used outside of the industrial coatings arena. Methylene chloride-based paint strippers were used for removing coatings in the residential, commercial and light industrial markets for years, and the commercial aircraft industry used these strippers to remove coatings from the exterior of the fuselage. However, when chlorinated solvents became recognized as carcinogens (cancer-causing agents), their use as paint strippers declined. Other paint strippers came onto the market, and were formulated to work on a variety of surfaces, including wood, steel, etc. These paint strippers were caustic-based (pH 14), and attacked the resin component of coatings, destroying their backbone and causing the coating system to debond from the underlying substrate. Caustic-based paint removers are the consistency of a heavy paste that is sprayed or troweled onto the surface. After a few hours of “dwell time,” the stripper is removed from the surfaces using scrapers, air or water pressure or even blasting with ice crystals. Multiple applications can be required, depending on the coating system and thickness. Neutralization of the surface after the stripper has been Chemical Stripping removed is required for proper coating performance. Environmentally and user-friendly chemical strippers are available that have a neutral pH and little odor. They rely on the metal surface below the coating to act as a “catalyst” that sets-off the stripping reaction. They are slower to work on thicker films, and metals in the coatings themselves may trigger the reaction, thus requiring several applications to remove multiple layers. Chemical strippers do not generate a surface profile, and will not remove rust or mill scale. Therefore, mechanical methods of surface preparation may be required after the coating has been removed or a coating system that is tolerant of intact mill scale and rust must Protective Coatings Inspector Training ©2015 SSPC
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be selected, provided it will perform adequately in the service environment. The use of chemical strippers is described in SSPC Technical Update (TU) 6, “Chemical Stripping of Organic Coatings from Steel Structures.”
Inspection of Surfaces for Primer Application After the specified level of surface cleanliness has been achieved and the surface profile depth has been measured and recorded, the inspector should verify that the prepared surfaces are ready for application of the primer. This includes dust removal, a final chemical contamination test (if required), measurement of the base metal effect (known as the BMR or Base Metal Reading), if required and verification that the time interval from surface preparation to primer application will not be exceeded. Dust/Debris Removal Dust and debris remaining on the surface must be removed by brushing, compressed air blow down (or double blow down), or by vacuuming the surfaces. If the compressed air blow down option is selected, then the compressed air must be verified for cleanliness by employing the blotter test (ASTM D4285) described earlier in this module. Compressed air blow down must be carefully inspected, as dust tends to cling to surfaces by static electricity. While a “white glove” test is not necessary nor recommended, if gloved fingers are traced across the surfaces and tracks are visually evident on the surface, then excessive dust remains and can interfere with primer adhesion and/or cause application defects. Alternatively, ISO 8502: Preparation of Steel Substrates Before Application of Paints and Related Products – Tests for the Assessment of Surface Cleanliness, Part 3: Assessment of Dust on Steel Surfaces Prepared for Painting (pressure-sensitive tape method) can be used to evaluated the presence of surface dust. To perform this test, a special type of clear, pressure sensitive adhesive tape (25 mm wide with an adhesion peel strength of at least 190 N per meter width), a special spring-tensioned roller, a 10X illuminated Protective Coatings Inspector Training ©2015 SSPC
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magnifier and a white board (e.g., bright white cardboard or poster board) must be acquired. Note: The spring-tensioned roller is relatively costly and is not required by the standard unless the testing procedure or results are being disputed. The roller can be replaced by thumb pressure applied to the tape, as described below). Step 1: Discard three full turns of tape from the roll. Step 2: Remove a test piece of tape approximately 200 mm long, being certain to only touch the two ends (25 mm at each end). Step 3: Attach (press) approximately 150 mm of the tape (excluding the two – 25 mm ends) to the surface. Step 4: Press the tape to the surface by placing your thumb at one end of the tape, then move your thumb along the tape length (at a constant speed and pressure) three times in each direction (each stroke should take between 5 and 6 seconds to complete). Leave the two 25 mm ends of the tape up off of the surface. Only the middle 150 mm of the tape should be attached. Note that thumb pressure must be replaced by a spring-tensioned roller in the case of disputes regarding procedure or test results. Step 5: Remove (peel) the tape from the surface at a 180o angle (to the surface) at a peel rate of 300 +/-30 mm/minute. Step 6: Attach the peeled tape to a white board (poster board). Step 7: Rate the quantity of dust attached to the tape using Figure 1 (Dust Quantity Ratings). If required by the project specification, rate the dust size attached to the tape using Table 1 (Dust Size Classes). These pictorial references are provided in the standard. Step 8: The standard requires one test for every 19 square meters (200 square feet) of prepared surface that is ready to be primed. Unless the project specification indicates otherwise, a dust quantity rating of 1 and a dust size rating of 2 or less is considered an acceptable surface for coating.
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Summary
While every phase of a coatings operation can contribute to the success or failure of a coating system, surface preparation is critical. Preparing the surface can also be the most costly phase of a coatings operation. However, not all surfaces require the same degree of surface preparation to accept a coating system, and not all service environments are as demanding on a coating system as others. Depending on the intended longevity of the installed coating system and the prevailing service environment, owners may be able to economize by specifying a lower degree of cleaning and selecting a coating system that can perform adequately over a lower level of surface preparation, or exposing existing surface roughness. Surface preparation has a two-fold purpose: cleaning and roughening the surface to successfully accept the coating. The inspector’s role in verifying cleanliness depends on what the specification requires. Typically, the level of cleanliness specified depends on the difficulties posed by the service environment. The specification may require the inspector to verify that grease, oil, and other contaminants have been adequately removed from the surface (SSPC-SP 1). This initial phase is referred to as pre-surface preparation and takes place before the actual surface preparation begins. During pre-surface preparation, an inspector’s responsibilities may also include verifying that structural deficiencies have been repaired, that weld spatter has been removed, and that edges and corners have been properly treated. This initial phase may also require testing for chemical contamination of the surface, as described in ISO Standard 8502 (Parts 5, 6, 9 and 10) and in SSPC-Guide 15. There are many methods that may be employed to prepare a substrate for the application of a coating system. Those methods include solvent cleaning, hand and power tool cleaning, dry and wet abrasive blast cleaning, chemical stripping and waterjetting. Centrifugal, diamond grinding and scarifying are also prevalent today. Dry abrasive blast cleaning is the most common method of surface preparation and Protective Coatings Inspector Training ©2015 SSPC
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can be used to roughen an existing coating system (to prepare for overcoating) or to remove the existing coating system completely. Of course, abrasive blast cleaning can also be used to prepare new steel for the application of a coating system. The International Standardization Organization (ISO), the Society for Protective Coatings (SSPC), and NACE International (NACE) have all developed consensus standards for surface cleanliness. More than one cleanliness standard may be invoked for a coating project and it is imperative that the coatings inspector understands both the intent, as well as the details, of each specification invoked. SSPC-SP 1 or “Solvent Cleaning” is a requirement in most of the cleanliness standards and requires the removal of all visible grease, oil, lubricants, cutting compounds and other non-visible contaminants from the surface prior to performing mechanical cleaning. Each cleanliness standard has been assigned a code by ISO, NACE, and SSPC, and each standard has a descriptive title, such as “Brushoff Blast,” “Commercial Blast,” Near-White Blast,” or “White Metal Blast.” The current standards define the level of cleanliness required, including the amount of mill scale, rust, paint, or staining (from those materials) that may or may not be allowed to remain on the surface, and two of the SSPC power tool cleaning standards (SSPC-SP 11 and SP 15) invoke a minimum 25 µm (1 mil) surface profile. While experienced inspectors are typically familiar with all of the cleanliness standards, it is always advisable to review the standard(s) invoked by a project specification in case there have been changes or recent updates. There are nine common “inspection check points” that may be required by the project specification relating to surface preparation. While not all of these checkpoints are required on every project, an inspector should be prepared to verify all of them whenever required. These common checkpoints include: 1. Receipt of contractor submittals (work plan, pollution control plan, QC plan and staging/access plan) 2. Verifying grease and oil removal by solvent cleaning 3. Measurement of ambient conditions prior to final surface preparation 4. Measuring blast nozzle air pressure and nozzle orifice size 5. Conducting an abrasive cleanliness test Protective Coatings Inspector Training ©2015 SSPC
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6. 7. 8. 9.
Conducting a compressed air cleanliness (blotter) test Assessing surface cleanliness Measuring surface profile depth Verifying surfaces are ready for primer applications
In addition, minimum lighting for surface preparation and inspection activities may be required by the project specification. The minimum and recommended lighting levels (based on the operations taking place) are provided in SSPC-Guide 12. The proper use of instrumentation and visual guides for performing the common inspection check points is one of the most important responsibilities of a coatings inspector. The step-by-step procedures for verifying the accuracy and using inspection instruments, visual standards and chemical contamination detection kits were described, and the common inspection instruments were made available for use in the workshop. If dry abrasive blast cleaning is part of the specification, an inspector may be required to verify the cleanliness of the abrasive blast media and the compressed air used in the blast lines. Dry abrasive blast cleaning can both clean a surface and roughen it at the same time; however, it is possible to achieve the correct level of cleanliness while not achieving the specified roughness. The reverse is also true. Therefore, the inspector must treat and verify cleaning and roughening as separate criteria. Dry abrasive blast cleaning is highly productive. While the level of cleanliness achieved depends on the distance that the nozzle is held from the surface and the “dwell time” the operator employs, the depth and shape of the surface profile are determined by the type and size of the abrasive. Both dry and wet abrasive blast cleaning requires an abrasive media. These abrasives fall into two categories: recyclable and expendable. Recyclable abrasives include steel grit, steel shot, and aluminum oxide. They can be used multiple times (steel grit, for example, can be used over 100 times with minimal breakdown), but they cannot be used in wet abrasive systems. Non-recyclable or expendable abrasives breakdown and are used once, then discarded, and many are ideal in wet abrasive systems. A project specification may invoke requirements for the abrasive itself. SSPC-AB 1 is an industry standard for mineral and slag abrasives, while SSPC-AB 3 Protective Coatings Inspector Training ©2015 SSPC
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governs newly manufactured metallic abrasives. These certifications are provided by the abrasive manufacturer. SSPC-AB 2 governs the cleanliness of recycled abrasive, which requires the contractor and the inspector to perform various tests on-site to prove the cleanliness of the abrasive as it is reused. SSPC-AB 4 governs recycled encapsulated abrasive media. Centrifugal blast cleaning is an automated, very productive form of blast cleaning, which is typically employed by fabrication shops. Centrifugal blast cleaning is ideal for large flat surfaces, and there are portable versions of this equipment that can prepare horizontal surfaces like ship decks or can be used to clean vertical surfaces, like the exterior of storage tanks. Vacuum blast cleaning is a much slower form of dry abrasive blast cleaning and is used when a high degree of cleanliness and surface roughness are required, but airborne abrasive and dust cannot be tolerated. Wet abrasive blast cleaning is another form of blast cleaning that can be used when airborne dust control is required by the specification. These processes can also reduce worker exposures when toxic metals and nuisance dust are generated during the coating removal process. The inspector’s role in achieving the specified roughness (also referred to as the surface profile or anchor pattern) may require verifying profile depth and uniformity over the project surface. Waterjetting is another widely used method of surface preparation. The variety of available water pressures can remove even tightly adhering coating systems. But while waterjetting can restore an existing profile or anchor pattern, it cannot create a new one. One problem with both wet abrasive blast cleaning and waterjetting is that any system that incorporates water will cause carbon steel to flash rust. Specifiers may require the use of a rust inhibitor or accept the flash rusting and select a coating system that is tolerant to flash rusting on the substrate. The final responsibilities of an inspector during the surface preparation phase of a coatings project are to verify that the prepared surfaces are free of dust and debris. Depending on the specification, there may also be a final test to determine whether surface chemicals are at tolerable Protective Coatings Inspector Training ©2015 SSPC
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levels. And since many projects require the prepared surfaces to be primed within four hours or within the same shift, it is up to the inspector to verify that this timeframe has been met. Even when the timeframe has been met, if surface rusting occurs prior to application of the primer, the surfaces must be re-prepared to achieve the specified level of cleanliness. Throughout this module, we’ve stated that surface preparation is critical to the success or failure of a coating project. The quality and dependability of the verification process is also critical. Once a primer has been applied to the substrate, it is nearly impossible to determine the level of surface cleanliness and surface profile achieved without destructive examinations. Therefore, a coatings inspector must observe and verify that the pre-surface and surface preparation procedures have been performed according to the specification before the primer is applied. The informed, ethical inspector is the key to this process.
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Module Three Surface Preparation: Methods, Industry Standards and Inspection
Introduction (Module Content) n n
n
n n n
Module Three Learning Outcomes n
Comprehension of Module Three will enable the participant to: Ø Ø Ø Ø Ø Ø Ø
n
Overview n
Describe the importance of proper surface preparation Explain the dual objective of surface preparation Describe methods used to control an environment during surface preparation activities Define the standards for surface preparation Describe common methods used to prepare surfaces for coating Measure and record surface profile Evaluate surface cleanliness
Surface Preparation Dual Purpose: Ø Cleaning
the surface Ø Roughening the surface
Must be inspected for separately n Often two distinct acceptance criteria n
Preparing the surface for the application of the coating system is: Ø Ø Ø
Critical Often expensive A key factor in determining the service life of the coating system
Methods of Surface Preparation n n n n n n n
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Pre-surface preparation Methods of controlling environmental conditions Methods used to clean and roughen surfaces Surface cleanliness standards Surface preparation equipment Inspection of surface preparation
Solvent cleaning Hand and power tool cleaning Dry abrasive blast cleaning Wet abrasive blast cleaning Chemical stripping Waterjetting Non-traditional (cryogenic, pliable media…)
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Inspector Responsibilities for Surface Preparation The role of the inspector is “OADR”: Observe, Assess, Document and Report. n The following checkpoints may be required when inspecting. n Remember to Document and Report all test results n
Inspector Responsibilities for Surface Preparation n
May include verification of:
Common Surface Preparation Inspection Checkpoints
2.
3.
4.
5.
n
Many specifications require a “presurface preparation inspection” to verify that: Ø Fabrication
defects are corrected Ø Surface contamination is sufficiently removed Ø Only invoked if required by the project specification
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7.
8.
Assessing surface cleanliness Measuring surface profile depth Verifying surfaces are ready for primer application
May also include verifying that: Structural deficiencies have been repaired The contractor’s equipment is operating properly (to maintain schedule) Ø Review/verify adequacy of submittals
cleanliness Ø Compressed air cleanliness Ø Adequate removal of grease, oil and other contaminants (SSPC-SP 1) Ø Degree of surface cleanliness and roughness
n
6.
Additional Inspector Responsibilities for Surface Preparation
Ø Abrasive
Pre-Surface Preparation Inspection
Verify grease and oil removal by solvent cleaning Verify ambient conditions prior to final surface preparation Conducting a compressed air cleanliness (blotter) test Measuring blast nozzle pressure and nozzle orifice size Conducting an abrasive cleanliness test
1.
Ø Ø
– – – –
PCP Work Plan Abrasive certifications Staging and containment plan
Pre-Surface Preparation Inspection n
Weld Spatter Ø
Ø Ø
Ø
Ø
Stick, flux core, MIG or TIG welds Can result in spot corrosion Specification may require removal Coatings may not flow over weld spatter Spatter may become dislodged in service
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Module 3 - Surface Preparation: Methods, Industry Standards and Inspection
Preparation of Welds – Immersion Service n
Appendix C of NACE SP0178 Five degrees of surface finishing of welds Ø Supplemented with molded plastic weld replica comparator Ø
Pre-Surface Preparation Inspection n n n
Ø
n n
Pre-Surface Preparation Inspection n
Treatment of flame cut edges important Often sharp Heat causes hardening of steel surface Ø Abrasive blast cleaning may not generate adequate profile depth Ø Grinding removes surface hardening
n
Ø
n
Laminations Ø
Ø
Ø
Ø
Ø
Occur during rolling process May be raised by abrasive blast cleaning May project above coating if not removed Typically removed by grinding Affected area may require re-blast cleaning
Protective Coatings Inspector Training ©2015 SSPC
2 mm (1/16”), 4 mm (1/8”) radius or chamfer; “break”
May requiring “striping” SSPC Guide 11
Stripe Coating (striping)
Ø
Pre-Surface Preparation Inspection
Sharp edges and corners Coating “draws thin” Specification requirements for edge preparation vary
n n
Additional coating layer on welds, edges, bolt heads, nuts, around rivets, etc. Brush or spray More detail in Module 5
Common Steel Defects: Severe Section Loss n
n
n
Older structures may exhibit severe section loss Structural engineers may require replacement or repair Inspectors verify that work is completed and acceptable to the structural engineer
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Module 3 - Surface Preparation: Methods, Industry Standards and Inspection
Pre-Surface Preparation n
Removal of Surface Contaminants oil, cutting compounds and/or lubricants Ø Chemical contamination
SSPC-SP 1, Solvent Cleaning n
Ø Grease,
n
n n
Requires the removal of all visible grease, oil, lubricants, and cutting compounds from the surface Degreasing agents (solvents, alkaline and emulsion cleaners, steam cleaning) described earlier Mechanical cleaning will not remove grease/oil “Indirect requirement” to the SSPC surface cleanliness standards
Removing Grease and Oil from the Surface
Removing Grease and Oil from the Surface
Solvents like methyl ethyl ketone (MEK), xylene or others n Other cleaning methods include detergent, alkaline, emulsion, steam
n
n
Solvents are: Effective degreasers Toxic Ø Flammable Ø Ø
n n
Proper use, ventilation and disposal critical Chlorinated solvents (e.g., methylene chloride): Ø Ø
Removing Grease and Oil from the Surface n
Removing Grease and Oil from the Surface
Non-solvent degreasers
n
Water with detergent Ø Alkaline cleaners (TSP)
n
Ø
– –
Ø
Requires thorough rinsing to remove soapy film May require testing for residual surface alkalinity
Emulsion cleaners (oil soaps diluted with Kerosene or mineral spirits) –
Carcinogenic Cannot be used on stainless steel
n
Steam 150°C (300°F) water Combination steam and pressurized water Alkaline cleaner can be added
Requires thorough rinsing to remove surface residue
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3-110
Module 3 - Surface Preparation: Methods, Industry Standards and Inspection
Inspecting Surfaces for Grease/Oil Contamination
Chemical Contamination on the Surface Chemical contaminants include chloride, ferrous ions, sulfates and nitrates n Deposited onto surfaces while structure is in service n Deposited during transportation of new steel to the fabrication shop n Water Soluble n
n
n n
Visual or wiping methods Black light detection Water break test
Removal of Chemical Contamination n
n
n
More difficult to remove from rough or pitted surfaces & crevices Pressure washing or water jetting using clean water is common Proprietary salt removal-enhancement solutions available
Testing for Chemical Contamination n
Specific ion (salt-specific) Chloride Ø Sulfate Ø Ferrous ion Ø
n n n
Conductivity (non salt-specific) ISO 8502-9 SSPC Guide 15 (Field Methods for Retrieval and Analysis of Soluble Salts on Steel and Other Non-porous Substrates)
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Chemical Contamination: Salts n
n
Undetected or inadequately removed salts can become trapped beneath a newly installed coating system Potential for osmotic blistering, underfilm corrosion, and premature coating failure
Testing for Chemical Contamination n n
Specification may prescribe methods of sample retrieval and analysis Retrieval methods include: Ø Ø Ø
n
Swabbing Latex patches Latex sleeves
Methods of analysis include: Ø Ø Ø Ø Ø
Chloride strips and tubes Drop titration for chloride Ferrous ion strips Conductivity meter (non ion-specific) Turbidity meter (sulfate)
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Module 3 - Surface Preparation: Methods, Industry Standards and Inspection
Latex Patch/Cell Sample Retrieval Steps
Chloride Titrator Strip Analysis Steps
Calculating Surface Concentrations-Chloride (patch)
Conductivity Analysis Steps
Entry
Result
1.
PPM (from chart)
124 PPM
2.
Quantity of water
2 mL
3.
PPM x Quantity of Water
124 x 2 = 248 µg
4.
Area sampled
12.25 cm2
Micrograms ÷ Area Sampled 248÷12.25=20.2 µg/cm2
Verify accuracy of conductivity meter Measure conductivity of “blank” Measure conductivity of sample Deduct conductivity reading of “blank” from conductivity reading of sample
Note: Retain your Quantab strip for inspection documentation
Converting Conductivity to Surface Concentration Estimate of surface concentration n Assumption is sodium chloride n E = 0.5 x S x (V÷A) n
Ø E:
Surface concentration (μg/cm2) Ø S: Conductivity (μS/cm) Ø V: Volume of extraction solution used Ø A: Area of sample collection
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Converting Surface Concentration to Conductivity Estimate of conductivity n Assumption is sodium chloride n S = 2 x E x (V÷A) n
Ø S:
Conductivity (μS/cm) Ø E: Surface concentration (μg/cm2) Ø V: Volume of extraction solution used Ø A: Area of sample collection
3-112
Module 3 - Surface Preparation: Methods, Industry Standards and Inspection
Tolerable Levels of Chemical Contaminants n n
No industry standard Project specification indicates the maximum quantity of soluble salts that can remain on the surface and be coated over
Measuring Ambient Conditions & Surface Temperature n
n
n
Conditions obtained using sling, battery- powered, or electronic psychrometers Dry bulb/wet bulb instruments used with US Weather Bureau Psychrometric Tables or dewpoint disc calculator Surface temperature obtained using dial, thermocouple or non-contact instruments
Measuring Ambient Conditions n
n n
Using batterypowered psychrometers Saturate wick Operate until wet bulb stabilizes (typically 2 minutes)
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Measuring Ambient Conditions Prior to Final Surface Preparation n
n
If air temperature and relative humidity are such that moisture from the air condenses on the surface, the surface may flash rust Recommend verifying that the temperature of the surface is at least 3°C (5°F) higher than the dew point temperature (may be invoked by specification)
n
Measure conditions on-site, where work will occur
n
Measure conditions prior to start-up and at 4 hour intervals (more frequent if required)
Measuring Ambient Conditions n
n n
n
Using sling psychrometers Saturate wick Whirl 20-30 seconds until wet bulb stabilizes Record wet & dry bulb temperatures
Measuring Ambient Conditions n
n n
n
Using Psychrometric Charts Locate Chart Verify Barometric Pressure (30.0 in.) Intersect air temperature with wet bulb depression
3-113
Module 3 - Surface Preparation: Methods, Industry Standards and Inspection
n
Determining Dew Point Temperature
Determining Relative Humidity
Electronic Psychrometers
Measuring Surface Temperature
Measure/Report: Ø Ø
Ø Ø
Ø
n
Air Temperature Surface Temperature (ST) Relative Humidity Dew Point Temperature (DP) Spread between DP and ST
n
n
Documenting Ambient Conditions and Surface Temperature Condition
Data 5/13/02
Date Time
1300 hours
Dry Bulb Temperature (t)
16oC (60oF)
Wet Bulb Temperature (t’)
13oC (55oF) 3oC (5oF)
Depression (t-t’)
73%
Relative Humidity
11oC (51oF)
Dew Point Temperature
15oC (59oF)
Surface Temperature Measurement Location
Dial-Type Thermometer Thermocouple-Type Thermometers Infrared (noncontact) thermometers
Dehumidification Contractor/Facility Owner may elect to control the environment rather than postpone operations n Dehumidification (DH) equipment removes air moisture, reducing opportunity for condensation n Inspector verifies conditions meet the project specification n
West side of tank, ground level
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3-114
Module 3 - Surface Preparation: Methods, Industry Standards and Inspection
Dehumidification, con’t. n
DH accomplished by:
Dehumidification, con’t. n
Air cooled over refrigeration coils Ø Condensation occurs on coils and is collected Ø Dry air exits the DH system (at reduced temperature, humidity and dew point)
Ø Refrigeration Ø Desiccation
(liquid or solid sorption) of methods listed Ø Refrigeration and desiccation (solid sorption) most common for field work Ø Combination
Dehumidification, con’t. n
Desiccant Ø
Ø
Ø
n n n
Dehumidification, con’t. n
Air passed over/through granular beds or fixed desiccant structures Desiccant (silica gel or lithium chloride) is active and dehydrated (low vapor pressure) Desiccant absorbs moisture from air. Hydration reaction causes exothermic reaction (heated air), so may be used with refrigeration-type DH
Assessing Lighting You can’t inspect what you can’t see If you can’t see, you can’t inspect SSPC Guide 12: Minimum & recommended lighting Ø Instrumentation used to monitor light Ø
Protective Coatings Inspector Training ©2015 SSPC
Refrigeration Ø
Ø Compression
Sizing Equipment Ø Ø
Ø
Determined by size of area and level of DH desired Appropriate air-change rate dependent on: – Equipment – Geographical location – Climate – Season – Distance (equipment-to-enclosure) – Amount of air exhausted by other means
Equipment suppliers provide guidance
Assessing Lighting, con’t. n
Foot Candle Ø
n
Meter Candle (Lux) Ø
n
Amount of light emitted by a lit candle 1 foot away Amount of light emitted by a lit candle 1 meter away
Obtain minimum of five measurements
3-115
Module 3 - Surface Preparation: Methods, Industry Standards and Inspection
SSPC Guide 12 Lighting Requirements
Surface Cleanliness Standards
Operation
n
Meter Candle (lux)
Foot Candle
Minimum
Recommended
Minimum
Recommended
General Area
108
215
10
20
Surface Preparation
215
538
20
50
Coating Application
251
538
20
50
Inspection
538
2153
50
200
ISO Surface Cleanliness Standards n
ISO Standard 8501-1:
Two degrees of Hand and Power Tool Cleaning Ø Fours degrees of Abrasive Blast Cleaning Ø One degree of Flame Cleaning
International Standardization Organization (ISO) n SSPC and NACE
Assessing Surface Cleanliness n n
ISO 8501-1 Select “Before” Photo of Initial Surface Condition –
Ø
–
Ø
n
ISO St 2: Thorough Hand and Power Tool Cleaning “When viewed without magnification, the surface shall be free from visible oil, grease and dirt, and from poorly adhering mill scale, rust, paint coatings and foreign matter.”
Protective Coatings Inspector Training ©2015 SSPC
St 1, St 2, Sa 1, Sa 2, Sa 2 1/2, Sa 3
Select “After” Photo –
ISO Surface Cleanliness Standards
A, B, C, D
Determine level of cleanliness required by specification
e.g., B Sa 2
ISO Surface Cleanliness Standards n
ISO St 3: Very Thorough Hand and Power Tool Cleaning “(Same) As for St 2, but the surface shall be treated much more thoroughly to give a metallic sheen arising from the metallic substrate.”
3-116
Module 3 - Surface Preparation: Methods, Industry Standards and Inspection
SSPC Visual Guides for Surface Cleanliness n
n
n
n
SSPC VIS 1 (Abrasive Blast Cleaning) SSPC VIS 3 (Power and Hand Tool Cleaning) SSPC VIS 4/NACE VIS 7 (Water Jetting) SSPC VIS 5/NACE VIS 9 (Wet Abrasive Blast Cleaning)
Assessing Surface Cleanliness n
n ! ! ! !
n n
Images in ISO and SSPC guides rarely “match” actual conditions Establish a projectspecific surface cleanliness standard/ test section Use SSPC visual guides to “calibrate” the eye Preserve with clear sealer or photograph
! !
Hand Tool Cleaning n n
n
n
Wire brushes, scrapers Remove loosely adhering corrosion products, old paint and flaking mill scale Do not produce a surface profile Frequently used to prepare surfaces for spot touch-up (maintenance)
SSPC-SP 2, Hand Tool Cleaning-General n n
n
SSPC-SP 1 (solvent cleaning) is an “indirect requirement” Weld slag, flux and fume deposits should be removed from welds (per contract documents) Verify removal of dirt/debris generated by hand tool cleaning (blow down, brush, vacuum) Ø
If blow down, verify cleanliness of compressed air (“indirect requirement” of SP 2)
Protective Coatings Inspector Training ©2015 SSPC
SSPC-SP 2, Hand Tool Cleaning Requires removal of all loosely adhering rust, mill scale and paint n Remaining materials must be tightly adhering n Contract may require feathering n No surface profile requirement n
Inspection of SSPC-SP 2, Hand Tool Cleaning n n n
Verification of “intact” via dull putty knife blade (subjective evaluation) Establish project-specific cleanliness standard Visual verification using ISO 8501-1 or SSPC VIS 3 Prepared surfaces rarely match visual guides Excellent tool to “calibrate” eye and aid in establishing project standard Ø Use described later Ø Ø
3-117
Module 3 - Surface Preparation: Methods, Industry Standards and Inspection
Power Tool Cleaning n n n n n
n n n
Grinders Pneumatic chisels Needle scalers Rotopeens Can remove loose and tightly adhering corrosion products, paint and mill scale Impact tools can remove pack rust & stratified rust Some can produce an anchor pattern Feathering of intact coating typically required
Power Tool CleaningGeneral, con’t. n
Power Tool CleaningGeneral
Power tool selection
n
Ø Amount
of surface area to be cleaned Ø Surface configurations Ø What needs removed (mill scale, surface rust, pack rust, stratified rust, coating…) Ø Level of worker and environmental protection Ø Degree of surface roughness required
n
n
Ø
SSPC-SP 3, Power Tool Cleaning Requires removal of all loosely adhering rust, mill scale and paint n Remaining materials must be tightly adhering (dull putty knife test) n No surface profile requirement n
If blow down, verify cleanliness of compressed air (“indirect requirement” of SP 3, SP 11, SP 15)
SSPC-SP 11, Power Tool Cleaning To Bare Metal n
Requires: Removal of all loosely and all tightly adhering mill scale, rust and paint to expose the bare metal surface (traces of paint, rust and mill scale can remain in bottom of pits) Ø A minimum 25 µm (1 mil) anchor pattern Ø
n
Prepared surfaces should not be compared to abrasive blast cleaned surfaces Ø
n
Protective Coatings Inspector Training ©2015 SSPC
SSPC-SP 1 (solvent cleaning) is an “indirect requirement” of SP 3, SP 11, SP 15 Weld slag, flux and fume deposits should be removed from welds (per contract documents) Verify removal of dirt/debris generated by power tool cleaning (blow down, brush, vacuum)
Surface roughness characteristics are different
Profile must be measured using ASTM D4417, Method B, Profile Depth Micrometer
3-118
Module 3 - Surface Preparation: Methods, Industry Standards and Inspection
SSPC-SP 15, Commercial Grade Power Tool Cleaning n n
n n n
Requires removal of all loosely and tightly adhering mill scale, rust and paint Staining from rust, paint and mill scale permitted but must not exceed 33% (one third) of each 58 cm2 (9 in2) of prepared surface Traces of paint, rust and mill scale can remain in bottom of pits Minimum 25 µm (1 mil) anchor pattern Profile must be measured using ASTM D4417, Method B, Profile Depth Micrometer
Inspection of Power Tool Cleaning n n n n
SSPC-SP 3: Verification of “intact” via dull putty knife blade (subjective evaluation) SSPC-SP 11 and SSPC-SP 15 require visual inspection Establish project-specific cleanliness standards Visual verification using ISO 8501-1 or SSPC VIS 3 Prepared surfaces rarely match visual guides Excellent tool to “calibrate” eye and aid in establishing project standard Ø Use described later Ø Ø
SSPC-SP COM November 1, 2004
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