version 1, may 2005 sspc protective coatings … sspc-vis 1, “guide and reference photographs for...

SSPC Protective Coatings Inspector (PCI) Program

Version 1, May 2005

May 2013

40 24th Street, Sixth FloorPittsburgh, PA 15222 - 4656Phone: 412-281-2331Fax: 412-281-9993Online: www.sspc.org Copyright 2013 SSPC: The Society for Protective Coatings

SSPC: The Society for Protective Coatingsis 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, publica-tions, conferences, and a variety of online resources. SSPC currently has over 800 company members and more than 7,500 individual members worldwide.

SSPC offers you:

Abrasive Blasting Program (C7)Aerospace Coating Application Specialist Certification Program (ACAS)Airless Spray Basics (C12)Applicator Train-the-Trainer ProgramApplicator Training Basics (ATB) eCourseApplicator Training Specialty Module CDsBasics of Concrete Surface Preparation eCourseBasics of Estimating Industrial Coatings ProjectsBasics of Nonferrous eCourseBasics of Steel Surface Preparation eCourseBridge Coatings Inspector Program (BCI)Coating Application Specialist Certification Program (CAS)Concrete Coating BasicsConcrete Coating Inspector Program (CCI)Evaluating Common Coating Contract ClausesFloor Coating BasicsFundamentals of Protective Coatings (C1)Fundamentals of Protective Coatings (C1) eCourseInspection and DocumentationLead Paint Removal (C3)Lead Paint Removal Refresher (C5)Lead Paint Worker SafetyMarine CoatingsMarine Coatings eCourseMarine Plural Component Program (MPCAC, C14)Master Coatings Inspector Certificate (MCI) Natural and Accelerated Weathering of CoatingsNavigating Standard Item 009-32NAVSEA Basic Paint Inspector (NBPI)Thermal Spray Short Courses

Online eCoursesPlanning and Specifying Industrial Coatings Projects (C2)Planning and Specifying Industrial Coatings Projects (C2) eCoursePlural Component BasicsProject Management for the Industrial Painting ContractorProtective Coatings Inspector Program (PCI)Protective Coatings Inspector Program (PCI) OnlineProtective Coatings Specialist (PCS) ProgramQuality Control Supervisor (QCS)Quality Control Supervisor (QCS) eCourseSpecification EssentialsThermal Spray TrainingUsing SSPC PA 2 EffectivelyWebinarsWater Jetting Program (C13)

Standards and Publications

Annual Conference

Online Serviceswww.sspc.org

Monthly JournalJournal 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 412-281-2331; 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.

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Table of ConTenTs

Introduction

Welcome and Course Introduction ..................................................................................................... I-1Participation Guidelines ..................................................................................................................... I-2The Course Syllabus .......................................................................................................................... I-2An Introduction to SSPC’s Protective Coatings Inspector Training ................................................. I-3Module One: Protecting Metal Surfaces From Corrosion: The Role of High Performance Coatings ......................................................................................................... I-3Module Two: The Roles of Quality Assurance (QA) and Quality Control (QC) Inspectors on a Coatings Project ................................................................................................. I-4Module Three: Surface Preparation ................................................................................................... I-4Module Four: Practical Arithmetic for the Coatings Inspector .......................................................... I-6Module Five: Coating Mixing, Thinning, and Application ............................................................... I-6Module Six: Industrial Protective Coatings and Coating Systems .................................................... I-8Module Seven: Specialty Inspection Projects .................................................................................... I-8Module Eight: Coating Failures and Methods of Prevention ............................................................ I-9Module Nine: Inspector Safety .......................................................................................................... I-9Module Ten: Coatings Specifications ................................................................................................ I-9Module Eleven: Pre-construction Conference and Inspection Procedure Development ................. I-10Module Twelve: Project Inspection Workshop ................................................................................ I-10Module Thirteen: International Maritime Organization (IMO) ....................................................... I-11SSPC Protective Coatings Inspector Training and Certification Program ....................................... I-11Use of Materials and Textbooks ....................................................................................................... I-13An Orientation to the Coatings Industry and Key Organizations .................................................... I-13Learning Outcomes .......................................................................................................................... I-14

Module 1: Protecting Metal Surfaces From Corrosion: The Role of High Performance Coatings

Corrosion Defined ..............................................................................................................................1-1The Role of Protective Coatings in Preventing/Slowing Corrosion ..................................................1-2

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The Fundamentals of Corrosion .........................................................................................................1-2Energy Required to Convert Ores into Metals ...................................................................................1-4Dissimilar Metals ...............................................................................................................................1-5Corrosion Versus Oxidation ...............................................................................................................1-6What is Steel? ....................................................................................................................................1-6Weathering Steel ................................................................................................................................1-7How Coatings Protect the Substrate from Corrosion .........................................................................1-7Additional Cathodic Protection ..........................................................................................................1-8Summary ..........................................................................................................................................1-12

Module 2a: The Roles of QA and QC Inspection Personnel on a Coatings Project

Quality Assurance vs. Quality Control ............................................................................................2a-1Pre-construction (Pre-job) Conference ............................................................................................2a-7Development 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 ........................................................................................................................................3-1Module 3 Learning Outcomes ...........................................................................................................3-2Overview ............................................................................................................................................3-2The Inspector’s Role ..........................................................................................................................3-3Purpose of Surface Preparation ..........................................................................................................3-3Inspection of Surface Preparation ......................................................................................................3-3Review of Industry Standards ............................................................................................................3-4Pre-surface Preparation Inspection ....................................................................................................3-7Preparation of Welds in Tanks and Vessels for Immersion Service ...................................................3-8Testing for Chemical Contamination ...............................................................................................3-16How Do I Test for Soluble Salt Contamination? .............................................................................3-17How Do I Test for Specific Ions and Conductivity? ........................................................................3-18Selecting a Field Sampling and Testing Method .............................................................................3-18

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Methods of Sample Collection

Surface Sampling Method A: Surface Swabbing (Swab SCAT Kit) ...............................................3-20Surface Sampling Method B: Latex Sleeve (Chlor*TestTM SCAT Kit) ...........................................3-20Surface Sampling Method C: Latex Cell (Bresle PatchTM and BresleSampler®) ...........................3-20

Methods of Sample Testing

Converting Between Surface Conductivity and Surface Concentration ..........................................3-21Analyzing Surface Extactions for the Sulfate Ion ............................................................................3-24Measuring Ambient Conditions .......................................................................................................3-23Using Electronic Psychrometers to Measure Ambient Conditions ..................................................3-24Using Surface Temperature Measuring Instruments ........................................................................3-26Calibrating Instruments for Measuring Ambient Conditions and Surface Temperature .................3-27Documenting Ambient Conditions and Surface Temperature .........................................................3-27Dehumidification ..............................................................................................................................3-28Assessing Lighting and Surface Cleanliness ...................................................................................3-31Methods of Surface Preparation .......................................................................................................3-33Selecting a Visual Standard..............................................................................................................3-39Using SSPC-VIS 3, “Guide and Reference Photographs for Steel Surfaces Prepared by Power and Hand Tool Cleaning” ...............................................................................................3-41Using SSPC-VIS 1, “Guide and Reference Photographs for Steel Surfaces Prepared by Dry Abrasive Blast Cleaning” ...................................................................................................3-59Using SSPC-VIS 5/NACE VIS 9, “Guide and Reference Photographs for Steel Surfaces Prepared by Wet Abrasive Blast Cleaning” ...............................................................................3-66Using the Surface Profile Comparator .............................................................................................3-84Project Specific Surface Cleanliness Standards ...............................................................................3-73Conducting a Compressed Air Cleanliness (Blotter) Test ...............................................................3-75Abrasives ..........................................................................................................................................3-77Abrasive Cleanliness ........................................................................................................................3-81Using the Surface Profile Depth Gage .............................................................................................3-84Measuring Surface Profile Depth .....................................................................................................3-82Using Replica Tape ........................................................................................................................3-84Calibrating Surface Profile Measuring Instruments .........................................................................3-86Documenting Surface Profile Measurements ..................................................................................3-86Using Portable Stylus Instruments for Determining Peak Density ..................................................3-87Waterjetting ......................................................................................................................................3-88SSPC/NACE Joint Surface Preparation Standards Waterjetting of Metals .....................................3-89

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Using SSPC-VIS 4 /NACE VIS 7, “Guide and Reference Photographs for Steel Surfaces Prepared by Waterjetting” ..........................................................................................................3-91Chemical Stripping ..........................................................................................................................3-98Inspection of Surfaces for Primer Application .................................................................................3-99Summary ........................................................................................................................................3-101

Instrument Use Supplement...............................................................................................3-137

Using Psychrometers to Measure Ambient Conditions .....................................................................1-2Using Electronic Psychrometers to Assess Ambient Conditions and Surface Temperature ..............1-8Using Surface Temperature Measuring Instruments ........................................................................1-17Calibrating Instruments for Measuring Ambient Conditions and Surface Temperature .................1-19Documenting Ambient Conditions and Surface Temperature .........................................................1-20Using the Keane-Tator Surface Profile Comparator ..........................................................................2-2Using Digital Surface Profile Gages ..................................................................................................2-5Using Replica Tape ..........................................................................................................................2-10Calibrating Surface Profile Measuring Instruments .........................................................................2-14Documenting Surface Profile Measurements ...................................................................................2-15How to Test for Soluble Salt Contamination .....................................................................................4-2How to Test for Specific Ions and Conductivity ................................................................................4-3Selecting a Field Sampling and Testing Method ...............................................................................4-4Collecting a Sample ...........................................................................................................................4-6Surface Sampling Method B ............................................................................................................4-10Surface Samping Method C .............................................................................................................4-12Testing the Collected Samples .........................................................................................................4-18Sample Testing Method 5: Conductivity .........................................................................................4-31Combination Extraction and Analysis .............................................................................................4-35

Module 4: Practical Arithmetic for the Protective Coatings Inspector

Learning Outcome .............................................................................................................................4-1Introduction ........................................................................................................................................4-2Averaging a Set of Values ..................................................................................................................4-2Converting Percentages to Decimal Format ......................................................................................4-4Calculating Area .................................................................................................................................4-5Converting Volatile Organic Compound (VOC) Content Values ....................................................4-17Converting Temperature ..................................................................................................................4-18

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Converting Units Used to Express Coating Thickness and Surface Profile Depth ..........................4-19Calculating Wet Film Thickness ......................................................................................................4-20Calculating the Target Wet Film Thickness .....................................................................................4-20Calculating Coating Coverage Rates and Estimating Material Quantities ......................................4-26Summary ..........................................................................................................................................4-31

Module 5: Coating Mixing, Thinning and Application: Equipment Overview and Inspection Techniques

Introduction ........................................................................................................................................5-1Learning Outcomes ............................................................................................................................5-2The Inspector’s Role ..........................................................................................................................5-2Review of SSPC Standards for Coating Application .........................................................................5-3Coating Manufacturer’s Technical Data Bulletins/Product Data Sheets ...........................................5-4Material Receipt Inspection and Storage Conditions .......................................................................5-14 Inspection of Mixing, Thinning and Application of Coatings .........................................................5-16Measuring Coating Temperature ......................................................................................................5-19Documentation and Reporting Procedures Relating to Inspection of Coating Mixing ...................5-20Coating Mixing Procedures .............................................................................................................5-20Coating Thinning Procedures...........................................................................................................5-24Inspecting Thinning Procedures.......................................................................................................5-27Documentation and Reporting Procedures Relating to Inspection of Thinning (reducing) ............5-28Coating Application Methods ..........................................................................................................5-28Spray Technique ...............................................................................................................................5-35Calculating Wet Film Thickness ......................................................................................................5-37Calculating the Target Wet Film Thickness .....................................................................................5-38Measuring Wet Film Thickness .......................................................................................................5-43Measuring Dry Film Thickness........................................................................................................5-44Measuring the Thickness of Individual Layers Using Destructive Means ......................................5-51Documentation Procedures Relating to Inspection of Dry Film Thickness.....................................5-53Assessing Intercoat Cleanliness .......................................................................................................5-54Detecting Amine Exudate (Blush) on Polyamide and Polyamide-Cured Surfaces .........................5-54Documentation Procedures Relating to Verification of Intercoat Cleanliness and Conformance to Recoat Intervals ..............................................................................................5-55Assessing Coating Cure ...................................................................................................................5-55Assessing Coating Film Hardness ...................................................................................................5-57Measuring Adhesion ........................................................................................................................5-60

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Detecting Pinholes and Holidays ....................................................................................................5-63Verifying the Accuracy of High Voltage Holiday Detectors ............................................................5-65Inspecting Fluorescent Coating Systems .........................................................................................5-66Summary ..........................................................................................................................................5-68

Instrument Use Supplement...............................................................................................5-101

Calculating Target Wet Film Thickness .............................................................................................5-2Measuring Wet Film Thickness .........................................................................................................5-5Adjusting and Using the Elcometer®456 wht PINIP™ Probe ........................................................6-23Adjusting and Using the Fischer Dualscope® MPOR.....................................................................6-27What is a Tooke Gage? ......................................................................................................................8-1Measuring Adhesion by the Knife Test (ASTM D6677) .................................................................9-11Measuring Pull-Off Adhesion (ASTM D4541; ASTM D7234) ......................................................9-13Measuring Adhesion Using the Elcometer® Model 106 .................................................................9-15Measuring Adhesion Using the HATE® Adhesion Tester ...............................................................9-22Measuring Adhesion Using the PATTI® Quantum Series Analog Adhesion Tester .......................9-28Measuring Adhesion Using the PosiTest® AT Adhesion Tester ......................................................9-38Special Requirements for Tensile Adhesion Testing of Coatings on Concrete ................................9-45Tensile Adhesion Testing: Record the Type and Location of Break ................................................9-47What are Pinholes and Holidays? ....................................................................................................10-1Selecting a Holiday Detector ...........................................................................................................10-2Using a Low-Voltage (Wet Sponge) Holiday Detector ....................................................................10-3Using a High-Voltage (Spark) Holiday Detector .............................................................................10-6Verifying the Accuracy of High-Voltage Holiday Detectors .........................................................10-11

Module 6: Industrial and Marine Protective Coatings and Coating Systems

Introduction ........................................................................................................................................6-1Industrial and Marine Protective Coatings Versus Paint ....................................................................6-3Industrial/Marine Coatings: Components ..........................................................................................6-3Curing Mechanisms ...........................................................................................................................6-8Identifying the Service Environment ...............................................................................................6-10Characteristics by Coating/Lining Type ..........................................................................................6-11Key Inspection Concerns by Coating/Lining Type ..........................................................................6-14Coating Systems Defined .................................................................................................................6-16

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Coating System Selection ................................................................................................................6-17Performance Evaluation of Protective Coating Systems .................................................................6-28Summary ..........................................................................................................................................6-30

Module 7: Specialty Inspection Projects

Introduction ........................................................................................................................................7-1Coatings Inspection in the Steel Fabrication Shop ............................................................................7-3Inspection of Thermal (Metallized) Spray Coatings (TSC) ...............................................................7-6Measuring the Thickness of Thermal Spray Coatings .......................................................................7-8Inspection of Powder Coatings ..........................................................................................................7-9Inspection of Galvanized Systems ...................................................................................................7-11Inspecting Overcoating Projects .....................................................................................................7-13Inspecting on Projects Involving Removal of Toxic Metal Coatings ..............................................7-18Summary ..........................................................................................................................................7-25

Module 8: Coating Failures: Consequences and Case Studies

Introduction ........................................................................................................................................8-1The Role of the Coatings Inspector in Failure Avoidance .................................................................8-3The Role of the Coatings Inspector in a Failure Investigation ..........................................................8-3Case Studies of Coating Failure .........................................................................................................8-4Summary ..........................................................................................................................................8-17

Module 9: Coatings Inspector Safety

Introduction ........................................................................................................................................9-1General Safety Responsibilities of the Coatings Inspector ................................................................9-2Inspector Medical Surveillance ..........................................................................................................9-3Safety Monitoring ..............................................................................................................................9-3Risks ...................................................................................................................................................9-4Types of Hazards ................................................................................................................................9-5Other Hazardous Materials Encountered by Inspectors .....................................................................9-9Hazardous Environments .................................................................................................................9-10Personal Protective Equipment ........................................................................................................9-15Summary ..........................................................................................................................................9-18

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Module 10: Navigating Coating Specifications

Introduction ......................................................................................................................................10-1Learning Outcomes ..........................................................................................................................10-1Purpose of a Coatings Specification ................................................................................................10-2Inspecting Against a Poorly Prepared Specification ........................................................................10-4Inspecting When There is No Specification .....................................................................................10-4Specifying Coating Systems ............................................................................................................10-5Components of a Coating Specification ...........................................................................................10-8Summary ........................................................................................................................................10-12

Module 11: Specification Review and Pre-Construction Conference; Inspection Plan Development for the Inspection of a “Bottomless” Tank Lining Installation

Introduction ......................................................................................................................................11-1Learning Outcomes ..........................................................................................................................11-1

Module 12: Simulated QA/QC Inspection of “Bottomless” Tank Lining Installation

Introduction ......................................................................................................................................12-1Learning Outcome ...........................................................................................................................12-1Workshop Instruction .......................................................................................................................12-1

Module 13: IMO Requirements

Introduction ......................................................................................................................................13-1Learning Outcome ...........................................................................................................................13-2Purpose of Standard [Paragraph 1] ..................................................................................................13-2Definitions [Paragraph 2] .................................................................................................................13-3General Principles [Paragraph 3.1-3.333] ........................................................................................13-3Coating Technical File [Paragraph 3.4] ...........................................................................................13-3Coating Standard [Paragraph 4.1-4.3] .............................................................................................13-5Basic Coating Requirements [Paragraph 4.4] ..................................................................................13-5Coating Inspection Requirements [Paragraph 6] .............................................................................13-7

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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 andModule 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

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.

I


Introduction

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.


Introduction

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.


Introduction

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


Introduction

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


Introduction

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


Introduction

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.


Introduction

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,


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


Introduction

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


Introduction

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 non-conformities 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


Introduction

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.


Introduction

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.


Introduction

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 ___________________________________________________


Introduction

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. Describe the common duties, responsibilities and the role of an industrial coatings inspector

2. Describe the authority of a coatings inspector3. Explain the importance of thorough documentation4. Identify the elements of a corrosion cell5. Describe the corrosion of metal surfaces6. Explain how industrial coatings control corrosion 7. Describe alternative methods used to protect carbon steel from

corrosion8. Describe the differences between quality assurance and quality

control9. Describe the common duties of quality assurance and quality

control personnel10. Describe the purpose and content of a pre-job or preconstruction

conference11. Explain the purpose of an inspection procedure/plan12. Explain the importance of inspection personnel13. Describe the importance of proper surface preparation 14. Explain the dual objective of surface preparation15. Define the SSPC standards for surface preparation16. Describe common methods used to prepare surfaces for coating17. Describe methods used to control an environment during surface

preparation activities18. Measure and record surface profile19. Evaluate surface cleanliness


Introduction

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 application23. Describe the role of the coating manufacturer on a coatings

project24. Use MSDS and product data sheets to verify safe and proper

mixing, thinning and application of coatings25. Describe the inspector’s role regarding coating material receipt

and storage26. Measure and record ambient conditions and surface temperature27. Calculate wet film thickness28. Measure wet film thickness29. Verify the currency of calibration and assess the accuracy of

nondestructive coating thickness gages30. Measure coating thickness using nondestructive gages31. Describe the SSPC standard for measurement of coating

thickness (SSPC-PA2)32. Measure coating thickness using destructive methods33. Detect pinholes and holidays34. Measure coating adhesion35. Evaluate coating cure36. Measure coating hardness37. Identify common coating defects38. Describe methods used to verify intercoat cleanliness39. Identify basic differences between house paint and industrial

protective coatings40. List volatile and non-volatile components of a coating41. Describe the functions of the resin, additives, pigments and

solvents in a coating42. Describe methods by which coatings cure43. Describe the procedures used to identify service environments44. List advantages and limitations of various generic types of

industrial coatings45. Describe functions of the primer, mid-coat and finish coat46. Identify common coating systems used by various industries47. Describe methods used to evaluate coating performance prior to

full scale installation48. 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


Introduction

52. Describe the function of a coating specification53. List the basic components of a coating specification54. List potential safety hazards associated with coatings inspection55. Describe the personal protective equipment used by a coatings

inspector56. Prepare an inspection plan/procedure57. Perform coatings inspection on industrial projects58. Compare inspection results to specification requirements 59. 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”

1-1Protective Coatings Inspector Training©2013 SSPC

Module 1 – Protecting Metal Surfaces From Corrosion: The Role of High Performance Coatings

Protecting Metal SurfaceS froM corroSion: the role of high

PerforMance coatingS1Corrosion 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



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. Anode2. Cathode3. Metallic pathway (connecting the anode and cathode)4. Electrolyte



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.

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.

Dry Cell Battery - Example of Galvanic (Electrochemical) Corrosion



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.

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.

Illustration of Corrosion Cell - Current Flows from Anode to Cathode, Anode Decays in Electrolyte

Solution



Common Metals Most Energy to Convert (Less Stable)

ZincAluminumCast IronCarbon SteelStainless Steel, Type 430, activeStainless Steel, Type 304, activeStainless Steel, Type 410, activeCopperBrassBronzeStainless Steel, Type 430, passiveNickelStainless Steel, Type 410, passiveSilverTitaniumStainless Steel, Type 304, passiveStainless Steel, Type 316, passiveZirconiumPlatinumGold

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.



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.

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.”

Oxidation



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.



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



(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.



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.



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.


Module 1 – Protecting Metal Surfaces From Corrosion: The Role of High Performance CoatingsModule 1 - Protecting Metal Surfaces From Corrosion: The Role of High Performance Coatings


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