Good Painting Practice

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SSPC-PS4.02

62&Z

T

ADOPTION NOTICE

SSPC-PS4.02, "Vinyl Painting System, Three-And Four-Coatrn was adopted on October 3, 1994 for use by the Department of Defense (DoD). Proposed changes by DoD activities must be submitted to the DoD Adopting Activity: Commanding Officer, Naval Construction Battalion Center, Code 156, 1000 23rd Avenue, Port Hueneme, CA 93043-4301. DoD activities may obtain copies of this standard from the Standardization Document Order Desk, 700 Robbins Avenue, Building 4D, Philadelphia, PA 19111-5094. The private sector and other Government agencies may purchase copies from the Steel Structures Painting Council, 4516 Henry Street, Suite 301, Pittsburgh, PA 15213.

Custodians: Adopting Activity Army -ME Navy -YD-1

Navy -YD-1 Air Force -99 FSC 8010

DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited.

Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from

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IHS--`,,,,`-`-`,,`,,`,`,,`---SSPC-PAINT25

ADOPTION NOTICE

SSPC-PAINT25, "Primer, Raw Linseed Oil and Aleyd, Red Iron Oxide, Zinc Oxide," was adopted on October 3, 1994 for use by the Department of Defense (DoD). Proposed changes by DoD activities must be submitted to the DoD Adopting Activity: Commanding Officer, Naval Construction Battalion Center, Code 156, 1000 23rd Avenue, Port Hueneme, CA 93043-4301. DoD activities may obtain copies of this standard from the Standardization Document Order Desk, 700 Robbins Avenue, Building 4D, Philadelphia, PA 19111-5094. The private sector and other Government agencies may purchase copies from the Steel Structures Painting Council, 4516 Henry Street, Suite 301, Pittsburgh, PA 15213.

Custodians: Adopting Activity Army-ME Navy -YD-1

Navy -YD-1 Air Force -99 FSC 8010

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IHS--`,,,,`-`-`,,`,,`,`,,`---SSPC-PAINT 1

ADOPTION NOTICE

SSPC-PAINT1, "Red Lead And Raw Linseed Oil Primer," was adopted on April 11, 1995 for use by the Department of Defense (DoD). Proposed changes by DoD activities must be submitted to the DoD Adopting Activity: Naval Construction Battalion Center, 1000 23rd Avenue, Code 156, Port Hueneme, CA 93043-4301. DoD activities may obtain copies of this standard from the Defense Printing Service Detachment Office, Bldg. 4D (Customer Service), 700 Robbins Avenue,

Philadelphia, PA 19111-5094. The private sector and other Government agencies may purchase copies from Steel Structures Painting Council, 4516 Henry Street, Suite 301, Pittsburgh, PA 15213-3728.

Custodians: Adopting Activity: Navy -YD1 Navy -YD1

(Project 8010-N998) unlimited.

IHS--`,,,,`-`-`,,`,,`,`,,`---FSC 8010

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W 2595532 0079382 T30 B

SSPC-PAINT2

ADOPTION NOTICE

SSPC-PAINT2, "Red Lead, Iron Oxide, Raw Linseed Oil And Alkyd Primer," was adopted on April 11, 1995 for use by the Department of Defense (DoD). Proposed changes by DoD activities must be submitted to the DoD Adopting Activity: Naval Construction Battalion Center, 1000 23rd Avenue, Code 156, Port Hueneme, CA 93043-4301. DoD activities may obtain copies of this standard from the Defense Printing Service Detachment Office, Bldg. 4D (Customer Service), 700 Robbins Avenue, Philadelphia, PA 19111-5094. The private sector and other Government agencies may purchase copies from Steel Structures Painting Council, 4516 Henry Street, Suite 301, Pittsburgh, PA 15213-3728.

(Project 8010-N997) FSC 8010

DISTRIBUTION STATEMENT A. Approved for public release; distribution is un1imited.

--`,,,,`-`-`,,`,,`,`,,`---Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS

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M 2575532 0079383 977

SSPC-PAINT 13

ADOPTION NOTICE

SSPC-PAINT 13, "Red Or Brown One-Coat Shop Paint," was adopted on April 11, 1995 for use by the Department of Defense (DoD). Proposed changes by DoD activities must be submitted to the DoD Adopting Activity: Naval Construction Battalion Center, 1000 23rd Avenue, Code 156, Port Hueneme, CA 93043-4301. DoD activities may obtain copies of this standard from the Defense Printing Service Detachment Office, Bldg. 4D (Customer Service), 700 Robbins Avenue,

Philadelphia, PA 19111-5094. The private sector and other Government agencies may purchase copies from Steel Structures Painting Council, 4516 Henry Street, Suite 301, Pittsburgh, PA 15213-3728.

(Project 8010-N996)

--`,,,,`-`-`,,`,,`,`,,`---FSC 8010

Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS

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LEAD PAINT REMOVAL GUIDES: SUPPLEMENT TO VOLUME 2

SSPC = GUIDE 61 (CON)

Guide for Containing Debris Generated During Paint Removal Operations

and

SSPC = GUIDE 71 (DIS)

Guide for the Disposai of Lead-Contaminated Surface Preparation Debris

STEEL STRUCTURES SSPC 92-07

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SSPC TITLESSYSTEM 91 W 8bè79LiO 0003359 T82 ~

~~

DISCLAIMER

These specifications, guides and recommendations have been developed in accordance with voluntary consensus procedures by SSPC Advisory Committees and

are believed to present good current practice. They are monitored and revised as practices improve, and suggestions for revision are welcome. Other methods,

materials, and specifications may be equally effective or superior. SSPC is not responsible for the application, interpretation, or administration of these specifications, guides and recommendations. Moreover, SSPC does

not issue interpretations of its specifications, guides or recommendations; and no person is authorized to issue an interpretation of an SSPC specification, guide, or recommendation on behalf of the SSPC. SSPC specifically

disclaims responsibility for the use or misuse of these specifications, guides and recommendations. The supplying of details about the patented formulations, treatments, or processes is not to be regarded as conveying any right or permitting the user of this manual to use or sell any patented invention.

When it is known that the subject matter of the text is covered by patent, such patents are reflected in the text.

This book or any pati thereof must not be reproduced in any form without the written permission of the publisher. First Edition

March 1, 1992

STEEL STRUCTURES PAINTING COUNCIL 4400 Fifth Avenue

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SSPC TITLE*A ** = 8627940 00034Lï 287 '1

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IHS--`,,,,`-`-`,,`,,`,`,,`---SSPC TITLEXA XX 8627940 0003420 TT9 STEEL STRUCTURES PAINTING MANUAL

Volume 1

GOOD PAINTING PRACTICE Third Edition

Executive Editor John D. Keane Editors

Dean Berger, Harold Hower, Bernard R. Appleman Assistant Editors

Joseph Bruno, Kitti Condiff, Mark O DonneII, Janet Rex, Aimee Beggs, Vilma Macura,

Terry Sowers, Monica Madaus

STEEL STRUCTURES PAINTING COUNCIL 4516 HENRY STREET, SUITE 301

PITTSBURGH, PA 15213-3728 I

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SSPC TITLE*A YS ôb2794O 0003421 935

This book or any pari thereof must not be reproduced

in any form without the written permission of the publisher. Third Edition

First Printing, January 1994 IBSN 0-938477-81-1

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SSPC TITLESA *Y = 8627740 0003422 87%

IHS--`,,,,`-`-`,,`,,`,`,,`---DISCLAIMER

The techniques, procedures, regulations and other information presented in this volume have been reviewed by experts in each field and are believed to represent good current practice. They are monitored and revised as practices improve, and suggestions for revision are welcome.

SSPC is not responsible for the application, interpreta-

tion, or administration of the information outlined here. SSPC specifically disclaims responsibility for the use or misuse of any product, procedure or technology or misinterpretations of any regulations referred to in this manual. The supplying of details about patented formulations, treatments, or

processes is not to be regarded as conveying any right or permitting the user of this manual to use or sell any patented invention.

When it is known that the subject matter of the text is covered by patent, such patents are reflected in the text. Ill

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IV

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SSPC TITLEXA XX Ab27940 0003424 b4V Table of Contents Page Foreword Chapter 1 .O INTRODUCTION SSPC Staff ... 1 Chapter 1.1 CORROSION OF STEEL -SIMPLIFIED THEORY

byF.L.LaQue ... 3 Chapter 1.2 PAINTS FOR ANTI-CORROSION SERVICE

byCliveH.Hare ... 10 Chapter 2.0 SU RFAC E PREPARATION

byH.William Hitzrot ... 19 Chapter 2.1 MECHANICAL SURFACE PREPARATION

byA.W.Mallory ... 22 Chapter 2.2 M ETALLI C ABRASIVES

byEinarA.Borch ... 32 Chapter 2.3 NO N-M ETALLIC ABRASIVES

by H. William Hitzrot.. ... 4 5

Chapter 2.4 ABRASIVE AIR BLAST CLEANING

byJim Bennett ... 52 Chapter 2.5 WATER BLAST CLEANING

byJim Bennett ... 64 Chapter 2.6 HAND AND POWER TOOL CLEANING

by Preston S. Hollister and R. Stanford Short ... .

--`,,,,`-`-`,,`,,`,`,,`---68

Chapter 2.7 FIELD SURFACE PREPARATION COSTS

byRobertB.Roth ... 75 Chapter 2.8 OTHER METHODS AND FACTORS IN SURFACE PREPARATION

by Bernard R. Appleman and John D. Keane ... 78 Chapter 2.9 CHEMICAL CLEANING

by Melvin H. Sandler and Sam Spring. ... 9 0

Chapter 3.1 SPECIAL PRE-PAINT TREATMENTS: PHOSPHATING

bySamspring ... 98 Chapter 3.2 PICKLING STEEL SURFACES

by D. W. Christofferson ... 10 4

Chapter 4.1 PAINT MATERIALS

by Sidney B. Levinson and Saul Spindel. ... 117

Chapter 4.2 ZINC-RICH PRIMERS

byCharlesG.Munger ... 125 Chapter 4.3 CORROSION INHIBITIVE PIGMENTS AND HOW THEY FUNCTION

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byArnoldJ.Eickhoff ... 138 Chapter 5.1 PAI NT APPLICATION

by Sidney B. Levinson and Saul Spindel.. ... 150

Chapter 5.2 SCAFFOLDING

Chapter 5.3 SAFETY IN PAINT APPLICATION

Chapter 6.0 INSPECTION

by Kenneth B. Tator and Kenneth A. Trimber ... 181

V

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SSPC TITLEXA Xt 8627940 0003425 580

Chapter 7.1 QUALITY CONTROL OF PAINTS -AS MANUFACTURED

by John F. Montle and Mary Ann Stephens ... 20 7

Chapter 7.2 QUALITY ACCEPTANCE OF PAINTS -AS RECEIVED BY THE USER

by John R. O Leary and Garland W. Steele ... 21 3

Chapter 8.0 COMPARATIVE PAINTING COSTS

by M.R. Sline, G. H. Brevoort, R. B. Feinberg,and S.J. Oechsle ... ... 222

Chapter 9.0 SHOP PAINTING OF STEEL IN FABRICATING PLANTS

byW.J.Wallace,Jr. ... 242 Chapter 10.0 PAINTING OF RAILROAD BRIDGES AND STRUCTURES

byRayeA.Fraser ... 263

Chapter 11 .O PAINTING OF HIGHWAY BRIDGES AND STRUCTURES

by R. R. Ramsey and Bernard R. Appleman ... 28 0

Chapter 12.0 PAINTING OF STEEL VESSELS FOR SALT WATER SERVICE

by David T. Bloodgood ... 293 Chapter 13.0 PAINTING OF STEEL VESSELS FOR FRESH WATER SERVICE

byJ.R.Foster ... 307 Chapter 14.1 PAINTING STEEL TANKS

byW.J.Wallace,Jr. ... 315 Chapter 14.2 THE LINING OF STEEL TANKS

by Wallace P. Cathcart and Albert L. Hendricks ... 320

Chapter 15.0 PAINTING HYDRAULIC STRUCTURES

byJ.L.Kiewit ... 330 Chapter 16.1 COATINGS FOR PIPELINES AND OTHER UNDERGROUND STRUCTURES

by R. N. Sloan and A. W. Peabody ...

--`,,,,`-`-`,,`,,`,`,,`---349

Chapter 16.2 CATH ODIC PROTECTION

byA.W.Peabody ... 363 Chapter 17.0 PAINTING OF INDUSTRIAL PLANTS

by William F. Chandler.. ... 37 7

Chapter 17.1 WASTE TREATMENT PLANTS

byThomasP.Delany ... 379 Chapter 17.2 PAINTING OF COKE AND STEEL PLANTS

by Arthur R. Thompson and S. C. Frye ... 3 90

Chapter 17.3 PETROLEUM REFINERY COATINGS

byW.E.Stanford ... 396 Chapter 17.4 PAINTING CHEMICAL PLANTS

by J. Roy Allen and David M. Metzger. ... 412

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Chapter 17.5 PAINTING PULP AND PAPER MILLS

by C. Edwin Wilkins and William F. Chandler ... 420

Chapter 17.6 PAINTING FOOD PLANTS

bySteven L.Schmidt ... 429 Chapter 17.7 POWER GENERATION FACILITIES

byRonald R.Skabo ... 442 Chapter 18.0 GOVERNMENT PAINTING PRACTICES

by Richard W. Drisko and Howard G. Lasser ... 4 48

Chapter 19.0 TRAINING PROGRAMS FOR PAINTING

byJayl.Leanse ... 452 Chapter 20.0 THERMAL SPRAYED COATINGS

by S.J. Oechsle and J. N. Childs, Jr. ... . 456

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Chapter 21.O Chapter 22.0 Chapter 23.0 Chapter 24.0 Chapter 25.0 Chapter 26.0 Chapter 27.0 Chapter 27.1 Chapter 27.2 Chapter 27.3 Appendix A Appendix B Appendix C Appendix D Index ... SSPC TITLEtA tt m 8b27940 000342b 417 HOT DIP GALVANIZING

byErnestW.Horvick ... 465

PAINTING GALVANIZED STEEL by Richard W. Drisko ... 481

CAUSES AND PREVENTION OF PAINT FAILURE by Charles G. Munger ... 486

PAINTING NAVY SHIPS by Stephen D. Rodgers, Richard W. Drisko and John Tock ... 5

16 DESIGN OF CORROSION-SAFE STRUCTURES byV.RogerPludek ... 528

SAFETY AND HEALTH IN THE PROTECTIVE COATINGS INDUSTRY by Dan Adley, D. Brian Shuttleworth, Scott Ecoff, Sidney Levinson and Saul Spind el . . 538

ENVI RON MENTAL REG U LATIONS AFFECTING PROTECTIVE COATINGS by Bernard R. Appleman ... 556

AIR QUALITY REGULATIONS by Bernard R. Appleman and Karen A. Kapsanis ... 56

0 WASTE HANDLING AND DISPOSAL by Bernard R. Appleman ... 573

OTHER REGULATIONS AFFECTING PROTECTIVE COATINGS by Bernard R. Appleman and Monica Madaus ... 580

ABBREVIATIONS ... 595

DEFINITIONS ... 596

STANDARDS AND SPECIFICATIONS REFERENCED IN VOLUME 1 ... 619

UNITS CONVERSION CHART ... 629

... 630

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IHS--`,,,,`-`-`,,`,,`,`,,`---SSPC TITLESA tX 9 8627940 0003427 353 FOREWORD

Coatings for structural steel have been called the principal means of protecting our principal construction material-steel-from its principal weakness-corrosion. This technology has been the subject of an intensive program by the Steel Structures Painting Council since 1950. The purposes of the SSPC are to assess and advance the technology of surface preparation and coating of industrial structures by conducting research, developing standards, and disseminating information: More specifically:

1. To instigate and carry on laboratory and field investiga- tions of techniques to mitigate corrosion through the use of protective coatings;

2. To develop standards, specifications, and guides covering techniques and materials of surface preparation and coating of structures; and

3. To organize and communicate information intended to further improve and make more effective the protection of industrial structures.

I. THE THIRD EDITION

The first undertaking of the Council was the preparation of Volume 1 of the Steel Structures Painting Manual. It has been revised since then to incorporate new information. This third edition of Volume 1, Good Painting Practice is primari- ly an editorial revision and update. A complete technical revision of the volume will take several years. In the interim, several chapters have been added and several have been

revised to reflect changes in the industrial painting industry since 1982.

One of the most important changes since that time has

been the increased attention health and safety and environmental regulators have focused on the industry. In addition to their other duties, specifiers and users must now be

familiar with hazardous waste, air pollution control and other regulations. Worker safety has also become a concern. In

recognition of the increased importance of these issues to painting concerns, an environmental chapter and a health and safety chapter have been added to the third edition. Concern about environmental and health effects has also

led to major changes in the kinds of paint the industry uses. Lead- and chromate-based paints, once a mainstay of the

industry, are being rejected in favor of less toxic paints. Most military and federal specifications for lead- and chromate- based paints have been canceled. SSPC has recently pro-

posed to withdraw its specifications for lead-based paint and is re-examining specifications for paints containing chromate pigments. At the same time, paints are being reformulated to meet air pollution control requirements, and the recent amendmentsto the Clean Air Act will accelerate this process. The tables in this volume have been revised in light of these new realities. Because the list of specifications in the back

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of Volume 2, Systems and Specifications has been enthusias- tically received, we have added such a list to Volume 1. Like its predecessors, the third edition is written from the coating end user s point of view and not that of the paint technologist or scientist. Volume 1 should be considered a companion to Volume 2. Volume 1 was intentionally designed to include some duplication between chapters. This tends to make each chapter as complete as possible for the industry being covered, to present shades of opinion with regard to various controversial matters, and to spare the reader the necessity of large amounts of cross-referencing. When such cross-referencing is necessary, however, it is expedited by the detailed Index, Glossary, Table of Contents and Specifi- cation list. Each chapter attempts to be a balanced presen- tation in which each author has been given the benefit of the viewpoints of the outstanding leaders in his particular

specialty, usually representing buyer, supplier, applicator, manufacturer, contractor, maintenance engineer and

engineer-architect. The focus, of course, has been on coatings for structural steel rather than factory-applied enamels. II. ABOUT THE SSPC

The SSPC is a professional technical society whose primary objective remains to improve the technology and practice of protecting structures through the application of coatings. Headquarters and laboratories of the SSPC are lo-cated in Pittsburgh. SSPC membership is open to both in- dividuals and organizations, but SSPC services are not

restricted to its membership. These services include consensus standards developed by technical committees, to help industry define and use good painting practice, a wide range of publications, and annual national conference and specialty conferences and tutorials offered throughout the year.

SSPC s laboratory evaluates new materials and application techniques and develops procedures for coating performance evaluation and surface characterization. SSPC s Painting Contractor Certification Program (PCCP) is a national, pre- qualification service developed for facility owners who hire contractors. The PCCP confirms that an industrial painting contractor has met the standards for quality set forth in SSPC-QP-1, Standard Procedure for Evaluating Qualifica- tions of Painting Contractors: Field Application to Complex Structures .

111. ORGANIZATION

The affairs of the Steel Structures Painting Council are managed by a Board of Governors composed of sixteen (16) elected members, a non-voting Secretary and Treasurer, and additional ex-officio members appointed by the President. The board of Governors annually elects a five-person Execu-

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tive Committee, consisting of the President, President-Elect, c.1.2 METALLIC COA TINGS

Vice President, and two additional members from the Board C.1.2.a Painting Galva nized Steel

of Governors. C.1.2.b Thermal Spray (Metallizing) The 6-member Standards Review Committee determines

whether a standard is consistent with the Bylaws, mission c.1.2.c Shop-Applied Zinc (inactive)

and overall best interests of SSPC and the industry before C.1.3 SOLVENTBORNECOA TINGS

the standard is sent to the Board of Governors for approval. C.1.3.a C.1.3.b

Coal Tar Epoxy (inactive) Chlorinated Rubber (inactive)

The Executive Committee of the Board of Governors

is responsible for the policy matters of the Council. It is elect- c.1.3.c

C.1.3.d C.1.3.d.l

Epoxy Polyamide (inactive) Polyurethanes

Thick Film Polyurethanes

ed annually, and is currently made up of the following: C.1.3.e Vinyls (inactive )

C.1.3.f Silicone-Containing Coatings (inactive) R. Dale Atkinson

John F. Montle

Brock Enterprises, Inc. Carboline President President-Elect C.1.3.g C.1.3.h Alkyds LOW-VOC Alkyds

William M. Medford North Carolina Vice President Department of

Transportation c.1.4 WATERBORNE COATINGS Bernie Beethe

R. Wayne Beason Bernie Appleman Company

American Steel & Aluminum Co., Inc. Texas Eastman

SSPC Secretary (Ex Officio) C.1.4.a

C.1.4.b C.1.4.c

Waterborne Epoxies Water Miscible Coatings Latex Coatings

Richard Benton Bob Washburne Dave Watson

Barbara Fisher SSPC Treasurer (Ex Officio) C.1.5 SPECIAL USE COATINGS

The following also served as members of the Board of Governors at the time of publication:

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C.1.5.a C.1.5.b C.1.5.c

Aluminum-Pigmented Coatings Marine Coatings

Weathering Steel coatings (inactive) Steve Delich Steve Draskovich Gary Tinklenberg Fred Beckmann Joseph L. Buerger Ed Darrimon Tom Dunkin, II

The American Institute of Steel Construction Procter & Gamble Company

Bay Area Coating Consulting Co Dunkin and Bush C.1.5.d C.1.5.e C.1.6 C.1.6.a C.1.6.b C.1.6.c

Surface Tolerant Coatings

Coatings Under Fireproofing (inactive) Coatings & Linings for Concrete

Concrete Coatings

Floor Toppings for Concrete Coatings For Secondary Containment Tim Race Tim Leise Tim Leise Bob Ketterlin Tim Hyde Alan Holub

Marcel M. Gaschke CIBA-GEIGY

(Ex Officio) c.2-SURFACE PREPARATION E. Crone Knoy Tank Industry

Consultants, Inc c.2.0 Surface Preparation Steering Ken Trimber Richard Lavergne Transocean Anti- c.2.1 Abrasives Bill Hitzrot corrosion, Inc c.2.2 Abrasive Blast Cleaning (inactive)

Michael J. Masciale Mark S. Schilling Steven L. Schmidt Kenneth A. Trimber Charles H. Wyatt Valspar Corporation Unocal Corporation Porter International KTA-Tator Enviro-Air Corporation C.2.3 C.2.4 C.2.5 C.2.6

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Wet Blast Cleaning Visual Standards

Industrial Blast Cleaning Duane Bloemke

Jerry Woodson Lydia Frenzel Ken Trimber Ken Trimber

Technical Committees are standing or ad-hoc groups as- C.2.7

C.2.7.a

Soluble Salt Contamination Chloride Extraction

Simon Boocock William Johnson

signed to address a specific or general technical topic within the scope of SSPC. Activities of technical committees

include developing consensus standards and providing fo-g&3 APPLICATION, INSPECT ION, AND QUALITY CONTROL

rums for exchange of information on pertinent technical issues. Technical committees are open to those interested in participating in the above activities, including members and non-members of SSPC. C.3.0 C.3.1 C.3.2 c.3.3 Application Steering Application Methods

Paint Thickness Measurement Inspection TBA TEA Forrest Couch Dean Berger Dick Drisko

c.3.4 Quality Assurance Nick Kozuska COMMITTEES AND CHAIRMEN Stan Gillard

(1993) c.3.5 Applicator Pre-Qualification Ralph Trallo Eric Kline

Number Name Chair 0 METHODS FOR IMPROVED PERFORMANCE -c.1 COATING MATERIALS

C.4.1 Maintenance Painting TEA

c.1.0 Coatings Steering Mary McKnight C.4.2 Performance Evaluation Mary McKnight c.1.1 Zinc-Rich (Unit) Dan Griffin c.4.3 New Specifying Methods (inactive) C.l.l .a ZR Performance Specs (inactive) Gerald Evarts c.4.4 Economics AI Roebuc k

C.l.1.b ZR Topcoating Systems Gary Tinklenberg Gordon Brevoort C.l.l .c ZR Preconstruction Primers (inactive) John Peart Dick Drisko Joe Butler AI Kay AI Roebuck AI Beitelman Dick Wakefield Dean Berger Dick Hergenrother Jeff Jarboe

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Bill Johnson Clive Coady Susan Simpson Marcel Gaschke --`,,,,`-`-`,,`,,`,`,,`---SSPC TITLEfA ft m 8627940 0003428 2îT m

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SSPC TITLEmA ** 8b27940 0003429 126 c.4.5 C.4.6 c.4.7 C.4.8 c.4.9 c.5 -C.5.0 C.5.1 C.5.1.a C.5.l.b C.5.1.c C.5.l.d C.5.1.e C.5.1.f C.5.2 c.5.3 C.5.3.a C.5.3.b C.5.3.d c.5.4 C.5.4.a -C.6 C.6.0 C.6.1 C.6.2 C.6.4 C.6.3 C.6.5 C.6.6 C.A -C.A.l C.A.2

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C.A.4

NACEISSPC JOINT TASK GROUPS SSPC/NACE TG A NACEISSPC TG B SSPCINACE TG C SSPCINACE TG D SSPCINACE TG E NACEISSPC TG F

--`,,,,`-`-`,,`,,`,`,,`---Bridge Painting Research John Peart Protective Linings Wallace Cathcart Tank Painting (inactive)

Pulp & Paper Industry Dennis Justice Accelerated Testing Simon Boocock

ENVIRONMENTAL, HEALTH AND SAFETY COMPLIANCE

Environmental, Health and Safety Steering Dan Adley IV. PUBLICATIONS

The Council makes available the results of its research, surveys and specifications work in a wide range of reports, manuals, conference proceedings and training videotapes

which are listed in its publications sheet and which include, in addition to Volumes 1 and 2, the following:

Individual specifications from Volume 2 on surface

preparation, painting systems, paints, application, safety, thickness and maintenance;

Photographic standards for surface preparation and degree of rusting;

SSPC National Conference proceedings, covering

protective coatings, surface preparation and compliance with environmental and health and safety regulations; Reports on laboratory and full coating performance

evaluation, influence of soluble salts, accelerated testing and maintenance of weathering steel;

Lead paint removal manuals, conference proceed- ing and reports;

Video tape training on Abrasives, Protective Coat- ings, and Application.

Bernard Appleman John Keane

Dean Berger Harold Hower September 1993 Safety and Health

Worker Protection Task Group (TG) Guidelines for Contract Documents Respiratory Protection TG

Safety and Health Guideline TG Technical Peer Review

Lighting in Containment TG Regulations & Litigation

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Hazardous Paint Removal and Disposal

Lead Paint Containment Lead Paint Disposal

Ambient Air Monitoring for Lead Paint Abatement

VOC Performance Reg-Neg Task Group

EDUCATION AND CERTIFICATION

Education & Certification Steering Education Main

Education Objectives & Curriculum Review

Certification Requirements PCCP Advisory

Local Chapter Education Policy Local and National Painter ComDetitions ADMINISTRATIVE Local Chapters National Conferences Volume 1 Revision Dan Adley Scott Ecoff Richard Thompson Bill Dixon Frank Pokrwyka Doug Stephens Richard C. Miller James A. Giese John Baker Lloyd Smith Ken Trimber Lloyd Smith Vincent Coluccio Bob Klepser Bob Klepser Steve Pinney Steve Pinney Harold Hower Ron Hayden Ralph Trallo Mark Schilling Richard LaVergne Ed Feige1

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Rose Mary Surgent Terry Sowers Ken Trimber Fred Lichtenstadter Carroll Steely Jerry Woodson Carroll Steely Lydia Frenzel Sy Solomon TBA Tom Aldinger Abrasive Blasting Thermal Cleaning Wet Abrasive Blasting Water Jetting

Solvent Cleaning Surface Preparation of Concrete

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SSPC TITLEtA tt 8627740 0003430 948 BIOGRAPHY BIOGRAPHY

Dr. Bernard R. Appleman

has been the Executive Director of the Steel Structures Painting Council since 1984. In this posi- tion, he is responsible for or- ganizing and managing

operations of a technical society whose activities encompass research, development of industry standards, and dissemination of technical information via reports, presentations, training programs and conferences. He has directed and coordinated

numerous projects in coatings performance evaluations, surface preparation techniques, development of specifications and guides, and lead paint removal and abatement.

His past work experience includes work as a CorrosionlCoat- ings Specialist for Exxon Research and Engineering Company. From 1977 to 1982, he was Project Manager, Coatings, for the Federal Highway Administration. He also worked as a Research Chemist for the Naval Ship Research and Development Center.

BIOGRAPHY

de Nemours and Company.

Mr. Keane is a member of various honorary societies, including Tau Beta Pi, Phi Lambda Upsilon, Pi Nu Epsilon and Alpha Chi Sigma. He has served as director of several civic and religious organizations and is the author of approximately 60 scientific and technical publications and 30 technical disclosures. He has represented the United States at three international symposia and conferences on coatings.

He served as a consultant, advisor, chairman, or active committee member in many societies, including the American institute of Steel Construction, the American Iron and Steel Institute, the Canadian Institute of Steel Construction, the Painting and Decorating Contractors of America, the Steel Plate Fabricators Association, the Federation of Societies for Coatings Technology, the American So-ciety of Association Executives, the National Paint and Coatings As-sociation, the National Association of Corrosion Engineers (NACE), the American Society for Testing and Materials, the Transportation Research Board, the International Organization for Standardization, and the American National Standards Institute. He is a Certified Manufacturing Technologist (Coatings), a NACE Corrosion

Specialist, and a registered professional engineer (by examination) in the states of Illinois, Pennsylvania and California.

Dean M. Berger received his B.S. degree at North Central College and did advance studies

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at the University of Wisconsin. He has had over 20 years of research experience at PPG Industries, and eight years at Union Carbide Research. Be- ginning in 1974, he worked for GilbetVCommonwealth, advising engineers and architects on the application and use of coatings. In 1988 Mr. Berger retired from Gilbert Associates and formed

his own coatings consulting firm, Berger Associates Inc., of Leola, Pennsylvania. He has attained specific expertise in zinc rich coating technology, epoxy, coal tar epoxy, urethane, and vinyl coating systems.

He has been a member of the Steel Structures Painting Council since 1960, chairman of the Epoxy Advisory Committee, and Co- Chairman of both the Research Committee and the Inspection Com- mittee. He was chairman of the American Society for Testing and Materials (ASTM) Subcommittee 0-1.46 on Industrial Protective

Coatings. He is the Executive Director of the Board of Registration of Nuclear Safety-related Coating Engineers and Specialists, and a member of ASTM Committee D-33 on Coatings for Power Gener-

ation Facilities. Mr. Berger is a recipient of the Man-of-the-Year Award from the Washington Paint Technical Group, and belongs

to the Gallows Bird Society. In 1957 Mr. Berger was President of the Pittsburgh Society for Coatings Technology Corrosion Commit- tee, and of the National Association of Corrosion Engineers (NACE). He is also a director of the Institute of Applied Technology, and a member of the American Water Works Association Committee D102. Mr. Berger is a licensed Professional Engineer in California, a Nuclear-Safety-Related Coatings Engineer, and a NACE Corrosion

Specialist. He has published over 100 technical articles and presented many papers on coating technology.

BIOGRAPHY

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SSPC TITLE*A Y* öb27940 0004097 T30 XII

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IHS--`,,,,`-`-`,,`,,`,`,,`---CHAPTER 1.0 INTRODUCTION

by

SSPC Staff

This Third edition of the Steel Structures Painting Manual, GoodPainting Practice, also known as Volume 1, carries for- ward the mission of the Steel Structures Painting Council: 1. To instigate and carry on laboratory and field inves- tigations of techniques to mitigate corrosion through the use of protective coatings;

2. To develop standards, specifications, and guides covering techniques and materials of surface preparation and coating of structures; and

3. To organize and communicate information intended to further improve and make more effective the protection of industrial structures.

The first edition appeared in 1954 and the revised is-

sue in 1964.The new edition is a technical update and editorial revision of the work that for nearly 40 years has been the

bible in protective anti-corrosion coatings. Its aims remain the same as that of the original: the manual is written from the viewpoint of paint users; it is not intended to be a scientific or highly technical treatise on paint formulation, but rather a practical encyclopedia on painting methods, equipment,

and systems that in the recent past have proved to be both economical and satisfactory.

The manual is still appropriate to the varied audiences

using it: contractors, engineers, specifiers, formulators, in- spectors, suppliers, technicians, maintenance painters,

users, and manufacturers. Given this wide audience with different levels of understanding about the subjects of the manual, it is necessary to present some material in a general rather than a detailed way, although some chapters have always been more detailed than others because the subject demanded it.

I. PRINCIPAL CHANGES

Volume 1 is intended as a companion to Volume 2,

Systems and Specifications . The latter was revised in

1991. Like Volume 2, it now includes a list of specifications referenced throughout the book.

During the last decade, there has been a tremendous increase in the number and the complexity of environmental and health and safety regulations. These regulations now apply in some way to most coating operations. Often, many different aspects of the same omperation are affected by a number of different regulations.

A new chapter has been added to cover the aspects of

environmental regulations that affect suppliers, specifiers, and contractors most: air pollution issues, particularly the

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recent Clean Air Act Amendments, hazardous waste disposal as well as the requirements of the Toxic Substances Con- trol Act, and requirements of the Clean Water and Safe Drink- ing Water Acts.

While worker safety regulations have not grown at the

same rate as environmental regulations, greater attention has been focused on health and safety aspects of coating operations, particularly exposures to lead. A revised health and safety chapter addresses the most important health and safety regulations facing coating applicators. Issues associated with exposure to lead in industries such as the coating industry are sufficiently distinct from those in general industry that OSHA recently issued a standard specifically address- ing such exposures in the construction industry. Those in the coating industry must also be concerned with exposures to solvents, safety when working at heights, the flammability of solvents and coatings and communicating chemical haz- ards to workers.

II. THE EDITORIAL PROCESS

All sections of the manual were reviewed to identify needed changes. Leading authorities in their fields were asked to review and update selected chapters. Some aspects of the coating industry have changed more than others. Wil- liam D. Corbett revised Chapter 6.0, Inspection . Gordon Brevoort revised Chapter 8.0, Comparative Painting Costs and John Tock revised Chapter 24.0 Painting Navy Ships . Dick Drisko rewrote chapter 22.0, Painting of Galvanized Steel. All specifications that have been canceled or fallen into disuse have been deleted from tables recommending

paint for particular uses. Several recent SSPC specifications have been added, and specification for paints using lead pigments have been deleted.

111. USING THE MANUAL

The reader of the Manual may wish to take advantage

of several features that may be helpful: the Table of Con- tents, Index, Glossary, Metric Conversion Table and List of Referenced Specifications. The Index, for example, makes

it possible to find both specialized information on a particular industry, and information applicable to most or all coating operations.

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SSPC CHAPTER*L.O 93 8627740 0003432 710 =

--`,,,,`-`-`,,`,,`,`,,`---Definitions common to most industries and practices are scientific to engineerin g to jargon in legitimate use in spe-

given in the Glossary. Even in these, considerable variation cial contexts. Prop rietary names have been avoided

exists within the standardizing bodies in the VariOUS indus- whenever a term cou ld be described in any other way.

tries involved. Whenever deemed necessary, definitions are included with the textual material, since terms range from

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SSPC CHAPTER*L-L 93 8627940 0003433 b57 CHAPTER 1.1 CORROSION OF STEEL -SIMPLIFIED THEORY by F.L. La Que

This chapter describes how steel corrodes. Because corrosion is the fundamental problem of coatings

technology, the discussion presents an explanation that will be useful to those who design and develop innovative protective coatings and to others who must put into practice the technology of coating systems.

Let us examine first the processes involved in the corrosion reactions that paint coatings will be required to suppress.

I. ENERGY EXCHANGE

Steel corrodes in reaction with its environment

because of the thermodynamically unstable condition of

iron after it has been extracted from its ores. Reduction of iron from its state as an oxide in ore requires energy in the reduction process. The fundamental laws of nature govern- ing conservation of energy require that, eventually, balance must be restored by return of the unstable metal

to its oxidized state. In the case of iron (steel) the oxidized state usually appears as rust. Rust is similar in ap-

pearance and practically identical in composition (Fe,O,) to the most common form of iron ore (hematite).

Appropriate conditions yield two other oxidized

forms, one of which has the same chemical composition

as a principal form of iron ore magnetite (Fe304). The other is the lowest oxide of iron, Feo. All three of these oxides are components of the mill scale formed on steel by ox-idation at temperatures encountered in the manufacture of steel into structural shapes and plates. Effects of such mill scale must be taken into account in preparing and painting steel to prevent corrosion.

The principal difference, in terms of energy, between reduction from ore and eventual conversion into rust by corrosion is not the amount of energy required but the rate of reaction. Fortunately, ambient environmental corrosion of iron proceeds much more slowly than high temperature oxidation. The principal function of a paint coating is to reduce the rate of corrosion in the environment and the area of the metal involved as much as possible, ideally to zero.

II. CORROSION PROCESSES

Understanding the process of corrosion provides the

key to steps that may be taken to prevent the reaction from occurring and to identify the role that paint can play in

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achieving this recul t.

Obviously, if the metal can be isolated from a cor-

rosive environment, no corrosion reaction can occur. Such isolation is the most important function of a paint coating. In addition, some constituents of a coating can suppress the rate of corrosion reactions where complete isolation is not achieved either generally or locally, as at pores, scratches or other discontinuities (holidays) in a coating. Consideration must be given, also, to the possibility

that a constituent of a coating might actually accelerate a corrosion reaction.

Experience has shown that corrosion in the presence

of a paint coating is likely to be much more serious where it is localized at discontinuities in a coating rather than where it occurs in a more general attack under a coating. This is true even if a coating is unable to isolate the metal from its environment. Consequently, what happens at

discontinuities in a coating as related to the processes of corrosion requires special consideration.

111. THE MECHANISM OF CORROSION

It has been well established by experimental demonstrati~n(~,~.~.~.~.~.~)

that corrosion is the result of an

electrochemical process involving an anodic reaction.

Here, the metal goes into solution as an ion, and acathodic reaction takes place where the electrons released by the anodic reaction are discharged to maintain electrical

neutrality by reaction with ions in solution, e.g. hydrogen ions in acid solutions, or by reduction of oxygen in solution in neutral or alkaline solutions.

The anode in a corrosion cell is analogous to the

negative zinc electrode in an ordinary dry cell battery. The cathode is analogous to the positive carbon electrode in such a cell. The current flows in the electrolyte inside the battery cell from the anode, zinc, to the cathode, carbon. The electrons generated by the cell move in the external circuit from the zinc electrode (-) to the carbon electrode k(+). By convention, the flow of current in the external circuit is opposite the electron movement.

Whether a particular area of a steel surface will act as an anode or a cathode will be determined by a number of factors. One factor is the condition of the thin, air-formed oxide films that exist on dry steel. Such films when they are intact induce a modest level of passivity that makes the film-covered surfaces more noble than, and therefore

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cathodic to, adjacent surfaces where a less protective film may exist.

Observations of steel surfaces after immersion in

water for several days have shown that, ordinarily, about 50% of the surface has been corroding as an anode with the remaining cathodic surfaces showing little or no evidence of attack. As time progresses, there is

breakdown of the protective films on the original cathodic surfaces so that corrosion spreads eventually over the whole surface. But a division between anodic and cathodic surfaces persists with the cathodic areas at any time being protected from corrosion by currents flowing from adjacent anodic areas.

Other factors in establishing anodic areas are dif-

ferences in crystal orientation, the presence of contamination on the surface of the steel, and, in exceptional cases, the effects of stresses above the elastic limit of the metal, which cause rupture of protective oxide films by plastic deformation.

Anodic areas can be established also by variations in the dissolved oxygen concentration of a solution in different zones on the steel surface. These variations can give rise to what is called an oxygen concentration cell in which current will flow from an anodic area in contact with the solution having the low concentration of dissolved oxygen to a cathodic area in contact with the solution having the higher concentration. The difference in corrosion potential that can be created by this mechanism on a steel surface can exceed 100 mV.

The anodic and cathodic reactions in the corrosion of iron can be written as follows:

At the anode where the metal goes into solution -Fe (solid) -Fe++ (ion) + 2e- (electrons)

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At the cathode

-2H' (hydrogen ions) + 2e--H, (gas) or 2H' + %O, (air) + 2e--.H,O

or O, + 2 H,O + 4e--4 OH- (hydroxyl ion)

The hydroxyl ions generated by cathodic reactions

can contribute to degradation of paints subject to attack by alkali.

Figure 1 helps to illustrate the process of corrosion. Iron ions (Fe++) released by the anodic reaction in-

teract with hydroxyl (OH-) ions generated by cathodic reactions to form Fe(OH), near the boundaries of anodic and cathodic areas. Oxygen reaching the precipitated Fe(OH), reacts with it to form Fe(OH), and, eventually, rust Fe,O,. The essential requirements for the electrochemical

reactions in corrosion are, therefore, a thermodynamically unstable metal, iron; an electrolytic conductor of ions, water or another conductive solution; an electrical conductor, the metal; and an electron acceptor, hydrogen ions or dissoIved oxygen.

We have the metal that we wish to protect from corro-

sion. What we need to control, therefore, is the availability of an electrolyte. This is best accomplished by an isolating barrier such as paint, or by reducing the concentration of electron acceptors such as hydrogen ions or dissolved oxygen.

4

IcATHODE,Y \CATHODE FIGURE 1

It may be possible under some circumstances to pre-

--`,,,,`-`-`,,`,,`,`,,`---vent corrosion by interfering with the anodic reaction by a process called passivation or reduction of the tendency of the iron to go into solution. In the case of steel, passiva tion usually is accomplished by very thin adherent oxide films which change the corrosion potential of the iron in the more noble direction (towards gold in the

elec-tromotive series).

Galvanic Corrosion Induced by Passivation

The change in potential of steel as a result of passivation, achieved for example by contact with passivating

pigments such as red lead and chromates, can create galvanic couples between the passivated iron under the paint film and adjacent unpassivated iron at bare spots. The result would be galvanic acceleration of corrosion of

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the exposed iron.

For this reason it Was been proposed that passivating pigments be excluded from paints used to protect steel under conditions of continuous or frequent, complete or partial immersion. However, with no more than the thin

film of electrolyte with limited electrical conductivity that will exist on surfaces exposed only to the atmosphere, a significant galvanic effect on a bare spot need not be an- ticipated. The benefit of passivating the bare spot by a pigment will more than offset the galvanic effect of passivation under the paint film. For this reason passivating pigments such as zinc chromate are beneficial rather than harmful in paints used for protection of steel in at-mospheric exposures.

In view of the fact that an electrolyte (water or

moisture) must be present for corrosion to occur, the principal function of a paint coating is to provide a barrier to penetration of water or moisture to the underlying metal surface.

Transfer of water or moisture through a paint coating can occur by water absorption by a coating or by transfer of water vapor through a coating. Details of these processes will be described in other chapters of this book. For the present it will suffice to note that penetration of water or moisture is accompanied by poor adhesion of the

coating to the metal. This permits osmotic effects to operate through the coating acting as a membrane and

thereby results in the development of blisters. Such action may be accentuated further by the superimposed effects of electrical currents created by corrosion, leading to the phenomenon of electroendosmosis5 with resulting blisters adjacent to cathodic areas.

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SSPC CHAPTER*L.L 93 m 8627940 0003435 42T m

IV. CORROSION AT DISCONTINUITIES IN A PAINT FILM

As noted previously, corrosion of steel associated

with paint films is most troublesome at, or adjacent to, pores, scratches or other bare spots. It is convenient, therefore, to examine the factors related to attack at bare spots. The most important of these factors is the location of the cathodic areas in the corrosion reaction. Possible locations of cathodic surfaces are shown diagrammatical- ly in Figure 2.

The extent of corrosion at an anodic area will be determined by the magnitude of the current generated by the local reactive corrosion cell. It will be governed by Ohm s law:

Equation 1

where I = corrosion current

E = difference in potential between anodic and cathodic surfaces

R = resistance of the circuit

When current flows in a corrosion cell, the initial

potential difference E is reduced by what is called polariza tion. The potential of the anodic surfaces drifts towards that of the cathodic surfaces as a result of an accumulation of corrosion products. The potential of the cathodic surfaces drifts towards that of the anodic surfaces as a result of accumulation of the products of the cathodic

reactions. The latter is affected by the rates of evolution of hydrogen as a gas or, more importantly in applications of steel, the rate at which oxygen in solution can react with

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electrons reaching cathodic surfaces after release by the anodic reaction. In most applications of painted steel the extent of cathodic polarization will determine the rate of the overall corrosion reaction. Anodic corrosion cannot occur at a rate higher than that accommodated by the

cathodic reaction.

Figure 3 illustrates the potential shifts that result from polarization. As indicated, polarization limits the amount of current that can flow. It will be reduced further by an increase in the resistance of the circuit.

POSSIBLE LOCATIONS OF CATHODES IN CORROSION CELLS AT BARE SPOTS IN A PAINT COATING ON STEEL ELECTROLYTE 7 1 AN OTHER METAL

PRIMER

(I) At Base Coating

(2) At Surface of Coating (3)At Base of Primer

(4) At Other Metal Surface FIGURE 2

EFFECTS OF POLARIZATION AND RESISTANCE ON CORROSION CURRENTS

I I I il 1 I 1 1

Corrosion Current Corrosion CurrZnt

Limited by Resistance Limited by Polarization and Polarization

FIGURE 3

As a result of polarization the original potential of the anode PA will be reduced by a factor Ap, and the original potential of the cathode PC will shift towards that of the anode by a factor Cp.

As a result, the effective potential difference (E) in equation 1 will become:

(PA -Ap) -(PC + Cp) and equation 1 becomes:

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I = (PA -Ap) -(PC + Cp) Equation 2 R

Let us now examine the factors that determine the magnitude of the resistance A.

These will include, in series, the resistance of the

electrolyte or whatever else occupies the discontinuity (D) in the coating (RDt), the resistance of the solution or film of moisture outside the discontinuity (RL), and the

resistance of the paint coating (C), (RCt).

The resistance of the metallic electron path is sufficiently low to be neglected.

The factor t in (RDt) and (RCt) takes into account the

fact that the resistance of the electrolyte within a discontinuity and the resistance of a coating will increase as the thickness of the coating is increased.

Combining all these component elements, the resistance factor R becomes:

RDt + RL + RCt and equation 2 becomes:

I = (PA -Ap) -(PC + Cp) Equation 3 RDt + RL + RCt

Now let us examine possible effects of the location ot the cathode on the corrosion reaction at the base of the discontinuity.

Location 1 in Figure 2 assumes that both the anodic

and cathodic reactions will have to occur at the base of a pore or other discontinuity in a coating. This automatically limits the area that can act as a cathode and, consequently, by increasing the cathode current density, increases favorably the value of the term Cp in equation 3.

Even more importantly, as the dimensions of the

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SSPC CHAPTERsL-L 93 H 8627940 000343b 3bb

discontinuity decrease and the thickness of the coating increases, the discontinuity resistance factor RDt may increase dramatically; especially when, as frequently oc-curs, the discontinuity becomes clogged with rust (Fe203) which has a very high electrical resistance.

The positive effect of thick coatings is shown by sea water tests of steel covered with a paint of proper thickness, but subsequently found to have many very

small pores. The steel showed no visible evidence of corrosion after immersion in sea water for more than a year. What has just been described supports the advantage

of increasing the thickness of a paint film, especially if the application involves exposure under conditions of

immer-sion.

The factor RL covering the resistance of the solution or film of moisture explains why corrosion is likely to be more severe in sea water than in fresh water and under conditions of immersion as compared with atmospheric exposure. In the case of the latter, humid atmospheres

containing chlorides, sulfur dioxide or other pollutants can promote more corrosion than dry, unpolluted

at-mosp heres.

The rather startling 8500 to 1 range in corrosivities of atmospheres was demonstrated by a test program undertaken by ASTM.6

The factor RCt, the electrical resistance of the

coating, becomes important only if the cathode of the corrosion reaction exists underneath the coating, (location 3, Figure 2). In such circumstances, favorable factors will be the thickness of the coating t and the resistance of the coating to water absorption and moisture penetration as well as its basic electrical resistance characteristics. A cathode created under a coating by the passivating action of primers containing inhibitive pigments such as red lead or chromates will have a low potential, Cp, and a relatively large area with low cathodic polarization, Cp in equation 3. Thus, the effect is to increase the corrosion current I. This supports the recommendation that

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passivating pigments should not be used in paints on steel in services involving continuous or frequent, partial or complete immersion.

As another example, it is possible also to create a

cathode under a paint film by migration of copper from an antifouling paint containing cuprous oxide or metallic copper.

Copper ions reaching the steel surface from an an-

tifouling paint can deposit on the steel by cementation and thereby become a powerful cathode to steel at the base of an adjacent discontinuity in a coating. Thus, an anti-fouling paint system based on copper must include an effective anti-corrosive film under the anti-fouling topcoat. Quite different from the thin invisible oxide films

formed on steel by exposure to dry air, mentioned above, are the relatively thick oxide scales formed on steel during high temperature manufacturing operations. This mill

scale has the composition Fe,O,. It exhibits a potential that in sea water can be more than 500 mV more noble

than that of bare steel. Metal exposed at discontinuities in such mill scale becomes the anode in a powerful galvanic cell with resulting severe localized attack at such anodic areas. The possibility of such effects produced by mill scale under paint coatings and the generally poor

adherence of mechanically disturbed mill scale account for the need to remove mill scale from steel in preparation of steel for painting.

V. EFFECT OF ANODIC PIGMENTATION

A very favorable condition can be achieved if a paint system includes zinc in either an organic or inorganic (silicate) matrix. Since zinc is anodic to steel, an anodic potential in the opposite direction is superimposed on the steel so that the factor in the numerator of equation 3 becomes zero or even negative and consequently the corrosion current I is eliminated. This accounts for the ex- cellent performance of zinc-rich coatings used either as primers or alone for protection of steel in marine and other severely corrosive environments. An essential requirement is that the zinc pigment loading be extensive enough to achieve electrical contact between the zinc particles so that they can function as effective galvanic anodes for the cathodic protection of the steel.

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It is unlikely that any paint system would create a

cathode at location 2, Figure 2, at the outer surface of the coating; however, this could happen in the case of an antifouling paint sufficiently loaded with copper powder or flake to form an effective copper cathode. Dangers from this source have restricted the use of antifouling paints based on metallic copper pigment.

Vil. EFFECT OF GALVANIC COUPLES

The most dangerous location of a cathode is location

4, Figure 2. This would be the case of painted steel in electrical contact with a more noble (cathodic) metal such as a copper or nickel alloy or stainless steel, both being immersed in an electrolyte.

Such a situation would provide a cathode much larger

than the very small anodes exposed at discontinuities in a paint film and with a large potential difference between the anode and the cathode (EA -EC), over 500 mV between the steel and the more noble metal.

The resulting galvanic corrosion would result in fairly rapid penetration (pitting) of the steel.

Painting the anodic (steel) member of such a galvanic couple will aggravate rather than minimize galvanic corrosion of the steel. It would be much better to leave the steel bare and tolerate the extent of the broadly spread galvanic corrosion that would result. But the best practice would be to paint both metals in the galvanic couple so as to

eliminate both galvanic and normal corrosion.

The next best choice would be to paint the more noble (cathodic) member of the couple and leave the steel bare.

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SSPC CHAPTER*L.L 93 8b27940 0003437 2T2 =

Discontinuities in a coating on the cathodic member can be tolerated in view of the small area of cathode that would become involved.

Coatings to be used on cathodic surfaces must be

able to tolerate the alkali generated by cathodic reactions. An interesting form of galvanic corrosion has been en-

countered in oil production systems in the North Sea. Here, steel drilling and production structures are associated with very large concrete vessels used for

storage of oil. The reinforcing steel embedded in the concrete can develop films that make the reinforcing steel strongly cathodic to steel outside the concrete. The

galvanic cell generated in this way can accelerate the corrosion of the outside steel. This can be particularly serious if the galvanic effect is concentrated at discontinuities in a paint coating. This could be a factor in deciding whether to use a paint coating as a supplement to cathodic protection and in determining the amount of current required for cathodic protection of the steel in the concrete. VIII. CATHODIC PROTECTION USED IN

CONJUNCTION WITH PAINTS

Cathodic protection can be achieved using either galvanic anodes (zinc, aluminum or magnesium) or im-pressed current systems as the source of the protective current. As in the case of cathodic protection from zinc in- corporated in a paint, the effect of the impressed current is to eliminate or change the direction of the potential difference in the numerator of equation 3.

Cathodic protection simply substitutes electrons from an external source for the electrons otherwise

generated in a corrosion cell to accommodate reduction of hydrogen ions and oxygen at the cathodic surfaces.

The electrical resistance of the coating (RCt) plays an important role in cathodic protection by increasing the

throwing power of the usually relatively small anodes by enabling the protective current to extend for greater distances from the current source.

It has been found that under severe service conditions a combination of a good paint system and cathodic protection is better than either one alone.

In addition to the throwing power effect, a paint system reduces the current required for cathodic protection by as much as 100to 1, depending on the condition of the paint.

Even when there may be no opportunity for renewal of

a paint system, its use can be justified in conjunction with cathodic protection in sea water. This is based on the

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probability that, in the course of time, the calcareous deposits created by cathodic reactions will replace the original paint system in achieving distribution of current and maintaining the level of current required for protection. O

Paint systems used with cathodic protection not only must tolerate attack by cathodic alkali, but must be protected from the danger of blistering by hydrogen which can result from too high a cathodic current density.

Cathodic protection is usually monitored and con-

trolled by measurement of the potential of the protected metal. This potential is measured relative to that of an appropriate bench mark reference electrode. One such

electrode is a saturated calomel half cell. It is assumed that protection of steel has been

achieved when its normal potential in sea water of about -600 mV has been raised to -850 mV.

Potential measurements can be used, as well, to

avoid hydrogen blistering of paints by restricting the potential resulting from cathodic protection. A conser-vative maximum polarized potential would be about -1000 mV versus a saturated calomel half cell. IX. EFFECTS OF STRAY CURRENTS

The advantage of a substantially intact paint film having high electrical resistance in connection with cathodic protection is reversed in situations, usually rare, where painted steel immersed in an electrolyte becomes involved in the passage of a stray electrical current. Under such circumstances the current is forced to leave the metal at discontinuities in the coating with consequent severe localized attack. This has been observed, for example, on painted ship hulls when an on-shore source of current for electrical welding on a floating ship has been provided with inadequate negative return cables. This leads to a substantial amount of current returning to ground through the water path in parallel with the return cable path. The effect is to increase greatly the anodic potential AP in equation 3 leading to a high corrosion current l concentrated at discontinuities in the coating.

X. EFFECTS OF COMPOSITION OF STEEL

Self-limiting forms of rust can offer protection to steel under certain conditions of atmospheric exposure. The

protective qualities of such rust films are affected by alloying elements and other minor constituents of steel. Cop-

per, chromium, nickel and phosphorus have beneficial effects. Sulfur has the greatest detrimental effect, which can be compensated for by the presence of copper in an

amount greater than the sulfur content.

Combinations of favorable alloying elements are

more effective than the same content of a single beneficial element. This is the case with the so-called high-strength, low-alloy steels. As measured by weight loss after exposure in certain corrosive atmospheres for 10 years,

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these steels showed an advantage over ordinary steel in a ratio of about 4 to 1or greater.

The advantage of the low-alloy steels is even greater

when the steels are painted, ,* as illustrated by Figure 4. Painted specimens of a steel of very low copper content have poor resistance to a marine atmosphere as compared with a better steel containing about 0.20% copper and an even better steel containing copper, nickel, chromium and phosphorus. The alloy steel suffered much less spreading of corrosion adjacent to the scribe marks in the paint. Further improvement was achieved by a phosphating

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SSPC CHAPTERaL.1 93 = 8627940 0003438 139 = Untreoted Surface

Open Heorth Iron 01% Cu Steei Cr-Ni-Si-Cu-P Steel

Bonderito Troated Surface

Open Hearth tron 0.2%Cu Steel Cr-Ni-Si-Cu-$ Steel FIGURE 4

Effect of Surface Treatment on Painted Steels Exposed Eight Months in Atmosphere 80 Feet from the Ocean at Kure Beach,

-N.C.

pre-treatment of the steel before painting. As measured by weight loss of scribed panels the advantage of the alloy steel over the poorest steel was in the ratio of 10 to 1. The combination of the phosphate pre-treatment and alloying

resulted in an improvement to a ratio of 20 to 1. The advantage of a low-alloy steel observed in at-

mospheric exposure is not duplicated under conditions of immersion. The better performance of the alloy steel in atmospheric exposure is based on the superior protective qualities of the thin film of rust that forms on the alloy steels, while the voluminous hydrated rusts that form on steels under conditions of immersion do not exhibit a similar difference in protective ability. Furthermore, the principal factors that influence corrosion under water, such as dissolved oxygen, effects of organisms and water

velocity, are external to the steel rather than related to its composition.

XI. CONCLUSION

Knowledge of the reactions involved in the corrosion of steel combined with a knowledge of how a paint system can impede these reactions and the qualities of a paint system needed to achieve the desired results, as de-scribed in the following chapter, along with proper

preparation of steel of desirable composition, can serve as an effective guide for using protective coatings to prevent corrosion.

ACKNOWLEDGEMENT

The author and editors gratefully acknowledge the active participation of the following in the review process for this chapter: Roy Boyd, Theodore Dowd, Richard Drisko, Arnold

Eickhoff, W.P. Gallagher, Clive Hare, William Hitzrot, William Mathay, Chuck Munger, Bruno Perfetti, Percy Pierce, Melvin Sandler, and William Wallace.

BIOGRAPHY

The late Francis L. LaQue, former Vice President of inco

Ltd., (formerly International Nick- el Co. of Canada), was often

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research and had a

distin-guished career in metallurgy. He devoted half his life to the research and development interests of the company, retiring in 1968, as Vice President and Special Assistant to the

President.

An honored member of many technical societies, Mr. LaQue

served as President of the National Association of Corrosion En- gineers from 1948 to 1949, the American Society for Testing and Materials from 1959 to 1960, the Electrochemical Society from 1962 to 1963, the American National Standards Institute from 1966 to 1971, and the international Organization for Standardization (ISO) from 1971 to 1973. He was a Fellow and Honorary Member of the American Society for Metals.