CORROSIONMcGraw-Hill Series in Materials Science and Engineering Editorial Board Michael B. Berer ‘Stephen M. Copley ME. Shank (Charles A. Wert Garth L. Wilkes Brick, Pease and Gordon: Structure and Properties of Engineering Materials Dieter: Engineering Design: A Materials and Processing Approach Dieter: Mechanical Metallurgy Dranglis, Gretz, and Jaflee: Molecular Processes on Solid Surfaces lemings: Solidification Processing Foatena: Corrosion Engineering Gaskell: Introduction 19 Metallurgical Thermodynamics Gay: Introduction to Materials Science Kebl: The Principles of Metallographic Laboratory Practice Lelie: The Physical Meillurgy of Steels [Rhines: Phaze Diagrams in Metallurgy Their Development and Application Rozenfeld: Corrasion Inhibitors Shewamoa: Transformations in Metals Saulth: Principles of Materials Science and Engineering Smith: Structure and Properties of Engineering Alloys Vander Voort: Metallography: Principles and Practice Wert snd Thomson: Physics of SolidsCORROSION ENGINEERING Third Edition Mars G. Fontana ‘Regents’ Professor and Chairman Emeritus Department of Metallurgical Engineering Fontana Corrosion Center The Ohio State University Executce Director Emeritus Materials Tecnology Institute of the Chemical Process Industries, In. f | | | McGraw-Hill Book Company New York St Louis San Francisco Aveklané Bogoti Hamburg london Madrid) Meuico Montreal New Delt Panama Paris S¥o Paulo Singapore Sydney ‘Tokyo TorontoCORROSION ENGINEERING INTERNATIONAL EDITION ‘Copyright © 1987 Exclusive rights by MeGraw-Hil Book Co — Singapore for manulacture and export. This book cannot be re exported from the country to which iis consigned by MeGraw-Hil 4567890 BJE 8932109 Copyright © 1986, 1978, 1967 by McGraw-Hill Inc ‘All ighs reserved. No part ofthis publication may be reproduced or dstnbuted in any form or by any means (or stored in a data base or retrieval system, without the prior writen permission ofthe publisher ‘The Editor was Sanjeev Rao “The Production supervisor was Maricta Breltwieser. Project supenision was done by Cobh/Duniop Publisher Services Incorporated “This Book was set in Times Roman Library of Congress Cataloging in Publication Data Fontana, Mars Guy, 1910 Corrosion engineering Bibliography: p. Inchuges index. 1. Corrosion and anti-corrosives. |. Tile. TARIB74 FS 1986 62011223 85-19713 SBN 0-07-021469-8 ‘When ordering this tte uso ISBN 0-07-100360-6 Printed in SingaporeMars G. Fontana is Regents’ Professor and Chairman Emeritus, Department of Metallurgical Engineering, The Ohio State University. He was the first Executive Director of the Materials Technology Institute of the Chemical Process Industries. He is a graduate of the University of Michigan, from which he received a bachelor’s degree in Chemical Engineering, M'S. and Ph.D. (1935) in metallurgical engineering, and an honorary Doctor of Engineering in 1975 ‘As a metallurgical engineer and supervisor (1934-1945) for the DuPont Company he pioneered industrial uses of nylon, Teflon, and other plastics, He joined the faculty of Ohio State in 1945 as a full professor and served as chairman of the Department of Metallurgical Engineering for 27 years. He established one of the first courses in the United States on corrosion in 1946. This same year he started the Corrosion Center, now the Fontana Corrosion Center. The Metallurgical Engineering Building was named the Mars G. Fontana Laboratories in his honor in May 1981 He was elected to the National Academy of Engineering in 1967, Heisan Honorary Member of the American Society for Metals, Cambell Lecturer in 1970, ASM Gold Medal, and Fellow, ASM, A.LCh-E, and A.LM.E. He was, President of the National Association of Corrosion Engineers in 1952 and received their Speller Award in Corrosion Engineering in 1956, He originated the use of high silicon iron anodes for cathodic protection and is the father of Alloy 20, He was the fist editor of the journal Corrosion. He has received several teaching awards, He has been consultant to industry and government since 1945, He has published over 200 papers in recognized journals. He is a ‘member of the Board of Directors of Worthington Industries (since 1973)To Betty, Martha, Marybeth, Dave, ‘Tom, Jeff, Steven, Brian, Sarah, Scott, Beth, Mike, Carley, Lauren, and Katie for all the time I spent away from them while preparing this third edition.CONTENTS Preface xvii Chapter 1 Introduction 1 141 Cost of Corrosion 1 12. Comoson Engincering 3 1.3 Definition of Corrosion 4 1-4 Environments 5 1S. Corrosion Damage 5 156 Castifeation of Corrosion 3 17 Future Outlook 9 Chapter 2. Corrosion Principles 12 241 Introduction 2 22 Corrosion Rate Expressions B letrochemical Aspects “ 23 Bletrochemical Reactions “ 24 Polarization 9 25° Pasiviy 2 Enviroumental fects a 246 Bifect of Oxygen and Oxidzers 2B 27 effects of Velocity a» 28 Effect of Temperature 6 29. Efe of Corotve Concentration 2% © 210 Met of Galvanic Coupling nvill contents Metallurgical and Orher Aspects 2-11 Metalic Properties 2.12 Beonamic Considerations 2.13 Importance of Inspection 24 New Instrumentation 215 Study Sequence Chapter 3. Eight Forms of Corrosion Uniform Attack Galvanic or Two-Metal Corrosion 341 EMPand Galvani Series 3:2. Eavironmental Effects 33° Distance Elect 34 Area Effect, 35 Prevention 346 Beneficial Applications (Crevice Corrosion 347 Environmental Factors 38° Mechanism 3.9 Combating Crevice Corrosion 3410 Fliform Corrosion Pring 311 Pit Shape and Growth 312 Avtocatalytc Nature of Piting 313. Solution Composition 3418 Velocity 34S Metallurgical Variables 3-16 Evaluation of Piting Damage 317 Prevention Intergranular Corrosion 3418 Austenitic Stainless Steels 319 Weld Decay 3.20 Conteol for Austenitic Stainless Stee!s 321 KnifeLine Atack 3-22 Intergranular Corrosion of Other Alloys Selective Leaching 3:23 Dezincication: Characteristics 3-24 Dezincification: Mechanism32s 326 37 328 Dezincifcation: Prevention Graphitization Other Alloy Systems High Temperatures Erosion Corrosion 329 330 331 ES cert 334 33 36 337 Surface Fils Velocity Turbulence Impingement Galvanic Effect Nature of Metal or Alloy Combating Erosion Cor Cavitation Damage Fretting Corrosion ‘Stress Corrosion Crack Morphology Suress Effects Time to Cracking Environmental Factors Metallurgical Factors ‘Mechanism “Maltienvironment Charts (Classification of Mechanisms Methods of Prevention Corrosion Fatigue Hydrogen Damage 8 9 350 31 32 355 Characteristics Environmental Factors Hydrogen Blistering Hydrogen Embrittlement Prevention Fracture Mechanics Chapter 4 Corrosion Testing 4 42 3 4 45 46 pe 48 o Iniroduetion ‘Cassifcation Purpose Materials and Specimens Surface Preparation Measuring and Weighing Exposure Techniques Duration Pranned-Interval Tests a8 » ® 0x conrents 437 Aeration ‘Cleaning Specimens After Exposure ‘Temperature Standard Expressions for Corrosion R Galvanic Corrosion High Temperatures and Pressures Erosion Corrosion Crevice Corrosion Intergranular Corrosion Huey Test for Stainless Stels ‘Streicher Test for Stainles Stels Warren Test iting Stress Corrosion NACE Test Methods Slow -Strain-Rate Tests Linear Polarization ‘AC Impedance ‘Small-Amplitude Cyclic Voltammetry Electronic Instrumentation In Vivo Corrosion Paint Tests ‘Seawater Tests Miscellaneous Tests of Metals, Corrosion of Plastics and Elastomers Presenting and Summarizing Data [Nomograph for Corrosion Rates Interpretation of Results Chapter 5 Materials sa Mechanical Properties 5:2 Other Properties Metals and Alloys $3 Cast Irons 5-4 High-Silicon Cast Irons 55 Other Alloy Cast Irons 546 Carbon Steels and Irons 5-7 Low-Alloy Stels 58 Stainless Stels 5.9 Aluminum and Is Alloys 5:10 Magnesium and Its Alloys S11 Lead and Its Alloys 5:12 Copper and Its Alloys 5-13 Nickel and Its Alloys 5-14 Zinc and Its AlloysS15 Tin and Tin Pate 5:16 Cadmium 5.17 Titanium and Its Alloys 5:18 Refractory Metals. 5.19 Noble Metals 5:20 Metalic Glasses 5:21 Metallic Composites [Nonmetallics| 5.22 Natural and Synthetic Rubbers 5:23. Other Elastomers 5:24 Plastics ‘Thermoplasties 5.25 Fluorocarbons 5.26 Acrylics 5:27 Nylon’ 5-28 Chlorinated Polyether 529 Polyethylenes 530 Polypropylene S31 Polystyrene 532 Rigid Polyvinyl Chloride (PVC) 533. Vinyls 5534 Other Thermoplasics Thermosetters 5.35 Eponies 536 Phenolics 537 Polyesters 5.38. Silicones 539 Ureas ‘5-40 Laminates and Reinforced Plastics (Other Nonmetalics SAL Ceramics 542 Carbon and Graphite 543 Wood Chapter 6 Corrosion Prevention Materials Seleeton 61 Metals and Alloys 62. Metal Purification 63. Nonmetalics contents xi 24 21 283 256 29 29 263 263 am mn am am m m 2m 24 m4 278 a 2m 280il conrents Alteration of Eaviroament 64 Changing Mediums 65 Inhibitors Design 66 Wall Thickness 67 Design Rules Cathodic and Anodic Protection 68 Cathodic Protection 69 Anodic Protection 610 Comparison of Anodic and Cathodic Protection Coatings 6-11 Metalic and Other Inorganic Coatings 612 Organic Coatings 613 Corrosion Control Standards 614 Failure Analysis. Chapter 7 Mineral Acids Saifurie Ald TL Stee 72 Castiron 73 Chemical Lead 7-4 HighSlicon Cast Iron 75 Durimet 20 7-6 Nickel-Molybdenum and Nickel-Molybdenum-Chromium Alloys 21 Combined Iscorrosion Chart 7-8 Conventional Stainless Sees 79 Monel, Nickel, Inconel, and Ni-Resst 7-10 Copper and Its Alloys TAAL Other Metals and Alloys 7.12, Summary Coart 7-13 Equipment at Ambient Temperatures 7-14 Sulfuric Acid Plant Equipment TAS. Nonmetallics Niele Ald 7-16 Stainless Stels 717 Class | Materials 7-18 Class 2 Materials 719 Class 3 Materials 7.20 Mined Acids ge 8 Bee S888 See 8 35Hydrochloric Acid a1 7 13 74 1s 126 ‘Class 1 Metals and Alloys lass 2 Metals and Alloys Glass 3 Metals and Alloys ‘Aeration and Onidizing Agents ‘Nonmetallic Materials ‘Hydrogen Chloride and Chlorine Hydrofoorie Acid 22 78 139 ‘Aqueous Hydrofluoric Acid ‘Anhydrous Hydrofluoric Acid Fluorine Phosphoric Acid 130 731 Materials of Construction Miscellaneous Chapter 8 Other Environments 84 82 2 64 BS 86 87 ry 9. 10 an B12 a3 ss Bas 8:16 87 a8 319 820 21 82 a2 424 825 826, a7 Organic Acids Alkalies “Atmorpherie Corrosion Seawater Fresh Water High-Purty Water Soils ‘Aerospace Petroleum Industry Biological Corrosion Human Body Corrosion of Metals by Halogens Corrosion of Automobiles "Nuclear Wate Isolation Liquid Metals.and Fused Salts Solar Energy Geothermal Energy Sewage and Plant-Waste Treatment Pollution Controt Coal Conversion Pulp and Paper Industry Dew Point Corrosion ‘Corrosion Under Insulation Blectronic Equipment Liquid-Metal Embrittlement or Cracking Hydrogen Peroxide Rebar Corrosion CONTENTS. xl as a7 351 382 382 353 337 337 387 4B ate 416 arabv conresTs 8.28 Botting 8.29 Statue of Liberty Chapter 9 Modern Theory—Principles 941 Introduction ‘and the EMF Series 94 Applications of Thermodynamics to Corrosion Bhectrode Kinet 9+ Exchange Current Density 96 Activation Polarization 9.7 Concenttation Polarization 9.8 Combined Polarization 9.9 Mixed-Potential Theory 9-10 Mined Electrodes 8.11 Passivity 9-12 Mechanisms ofthe Growth and Breakdown of Passive Films Chapter 10 Modern Theory— Applications 1041 Introdvetion Predicting Corrosion Behavoe 102 Effect of Oxidizers 103 Velocity Eflecs 10-4 Galvanic Coupling 10-5 Alloy Evaluation Corrosion Prevention 106 Anodic Protection 10-7 Noble-Metal Alloying Corrosion Rate Measurements 10-8 Tafel Extrapolation 109 Linear Polarization Chapter 11 High-Temperature Corrosion 11-1 Introduction Mechaniams and Kinetics Plling-Bedworth Ratio 11-3. Electrochemical and Morphological Aspects of Oxidation “3 445 4s, 4s “7 42 454 456 49 461 a 482 42114 Oxide Defect Structure su 11-5 Oxidation Kinetics 313 11-6 Effect of Alloying 516 14-7 Catastrophic Oxidation 318 M8 Internal Oxidation 319 ‘High-Temperature Materials 50 119. Mechanical Properties 50 11-10 Oxidation Resistance 504 Other Metal-Gas Reactions 3B 1-11 Decarburzation and Hydrogen Attack 3 11-12 Corrosion of Metals by Sulfur Compounds at High Temperatures 534 11-13 Hot Corrosion of Alloys sat Index 545PREFACE This third edition maintains the unique approach of the previous editions. It is unique because corrosion data are presented in terms of corrosives of environments rather than in terms of materials. This approach saves thumbing through many chapters on materials to determine likely candidate materials for a given corrosion problem (e.g., sulfuric acid). Isocorrosion charts (invented by the author) present a quick look at candidates for a Particular corrosive. ‘There are some exceptions to the above in Chapter 5, particularly When a material has outstanding characteristics for certain environments, Corrosion testing is the backbone of corrosion engineering. Chapter 4 includes simple and advanced complicated tests. Description of corrosion tests for plastics and elastomers has been expanded. The effects of the “revolution” in electronic instrumentation are described. Many types of electronic instrumentation are mentioned and references are provided for in-depth study. In response to requests to make the text more challenging to college students, some “cutting edge” items are included—for example, Sect 9-12, “Mechanism of the Growth and Breakdown of Passive Films.” ‘Advanced testing techniques such as AC Impedance and Small Amplitude Cyele Voltammetry (SACV) will be used more and more in the future Many environments have been added, such as the pulp and paper industry and nuclear waste isolation, and ‘also subjects such as fracture ‘mechanics and laser alloying, The need for more corrosion engineers to reduce the costs of corrosion is described. The enormous costs of product liability claims is emphasized, since producers must watch their p’s and q's, particularly QC and QA— quality control and quality assurance. wbAlthough this book was first written as a textbook, it has proved useful fas a reference book. The reference aspect has been enhanced through ‘provision of literature references for in-depth study. An improved index is presented Little attempt has been made to cover paints, cathodic protection, and water treatment comprehensively. These are more of an “art” (experience) than a science, and whole books have been written about them. References are provided. The novice should contact expert organizations in these fields, of which there are many. This text covers practically all the important aspects of corrosion ‘engineering and corrosion science, including noble metals, “exotic” metals, ‘onmetallics, coatings, mechanical properties, and corrosion testing, and includes modern concepts as well. This coverage eliminates some of the deficiencies of previous books on corrosion. The book is designed to serve ‘many purposes: It can be used for undergraduate courses, graduate courses, intensive short courses, in-plant training, self-study, and as a useful reference text for plant engineers and maintenance personnel Professors in metallurgical engineering, materials engineering, materials science, chemical engineering, mechanical engineering, chemistry, or other physical science or engineering disciplines could teach a beginning course Using this text without extensive background or much work in preparation. Section 2-15, “Study Sequence,” suggests different procedures depending ‘on the “needs” of the students, plant personnel, and others. This means that considerable flexibility exists for material to be covered or presented. Many examples are presented to illustrate the causes and cures of corrosion problems. Case histories are helpful in engineering teaching. Descriptions, including mechanical properties, of materials are presented so that the reader will get the proper “fee!” for materials. ‘A Solutions Manual is available as a separate booklet. In order to keep the price of the book down, the second edition (1978) consisted of the addition of an update, Chapter 12. In retrospect, this was less than a brilliant idea. Accordingly, Chapter 12 disappears; its infor- ‘mation is integrated into the other chapters. ‘The Materials Technology Institute of the Chemical Process Industries was established in June 1977 and 1 was the first executive director (now emeritus). Members of MTI pay dues and sponsor work by outside con- tractors on work of mutual interest. The main purpose is to provide the ‘corrosion engineer or materials engineer with tools and information to do his job more effectively. I am grateful to the board of directors of MTI for permission to use as much of the information developed as I wished. A substantial amount of this information and references to MT publications ‘appear in the book. ‘This edition is based on my $0 years of experience in industry, teaching, and consulting. Much of my time was devoted to solving corrosion problems.PRerAce xx 1 am happy to say that a large number of former students are successful corrosion engineers, and a score of them are teaching corrosion courses. I wish to gratefully acknowledge the assistance of my friends and colleagues with this revision for the third edition. These include David Bowers (Pulp and Paper Industry), Ron Latanision (Metallic Glasses), Digby Macdonald (Passivity Models, SACV, Electronic Instrumentation and review of Chapters 9 and 10), Mike McKubre (AC Impedance), Tom Murata (Sour Resistance, SR values), Tom Octtinger (Waste Treatment), Bob Rapp (High-Temperature Corrosion), Mike Streicher (Crevice Corrosion, CCD, John Stringer (Coal Conversion), and Dick Treseder (CO; Corrosion). All are experts in their particular fields of corrosion. also acknowledge other friends, former students, and colleagues in industry ‘who supplied data and photographs If this book results in the better education of many more people in the field of corrosion, particularly the young people in colleges and universities, and in a greater awareness ofthe cost and evils of corrosion as wel as of the ‘means for alleviating it, this book will have served its major purpose. | would like to express my thanks for the many useful comments and suggestions provided by colleagues who reviewed this text during the course of its development, especially to Judith Todd, University of Southern California, and Ellis Verink, University of Florida. Mars G. FontanaCHAPTER ONE INTRODUCTION 1-1 Cost of Corrosion Estimates of the annual cost of corrosion in the United States vary between ‘8 billion and $126 billion. I believe $30 billion is the most realistic figure, In any case, corrosion represents a tremendous economic loss and much can bbe done to reduce it. These large dollar figures are not surprising when we consider that corrosion occurs, with varying degrees of severity, wherever metals and other materials are used. Several examples follow. According to the Wall Street Journal (Sept. 11, 1981) cost to oil and gas producers is nearly $2 billion, Costs are increasing because of deeper wells and more hostile environments—higher temperatures and corrosive sulfur gases (e.g, 500°F and hydrogen sulfide) ‘Corrosion of bridges isa major problem as they age and require replace: ‘ment, which costs billions. The collapse (because of stress corrosion) of the Silver Bridge into the Ohio River cost 40 lives and millions of dollars. Corrasion of bridge decks costs about $500 million, Proper design and use of cathodic protection reduces costs substantially. One large chemical ‘company spent more than $400,000 per year for corrosion maintenance in its sulfuric acid plants, even though the corrosion conditions were not considered to be particularly severe. Another spends $2 million per year on painting steel to prevent rusting by a marine atmosphere. A refinery employ. ing a new process developed a serious problem afier just 16 weeks of opera- tion; some parts showed a corrosion loss of as much as 1/8 inch, The petroleum industry spends a million dollars per day to protect underground pipelines, The paper industry estimates corrosion increases the cost of Paper S6 10 $7 per ton. Coal conversion to gas and oil involves high2 conRESiON ENGINEERING temperatures, erosive particles, and corrosive gases, thus presenting severe problems that must be solved. Corrosion costs of automobiles—fuel systems, radiators, exhaust systems, and bodies—are in the billions. I personally incurred costs of $500 in refurbishing an automobile fuel system in which water had been mixed with gasoline! (A photograph of the gasoline tank ison the cover of Materials Performance, March 1982.) Approximately 3 million home water heaters are replaced every year. Corrosion touches all —inside and outside the home, ‘on the road, on the sea, inthe plant, and in aerospace vehicles. Total annual costs of floods, hurricanes, tornadoes, fires, lightning, and earthquakes are less than the costs of corrosion. Costs of corrosion will ‘escalate substantially during the next decade because of worldwide shortages of construction materials, higher energy costs, aggressive corrosion environ- ‘ments in coal conversion processes, large increases in numbers and scope of plants, and other factors. Political” considerations re also a factor. We depend largely on foreign sourees for some metals: 90 percent for chromium (the main alloying element for stainless steel) and 100 percent for columbium (niobium) used in temperature alloys. Our sources could be shut off or the prices boosted. For example, during a recent crisis the price per pound of columbium Jumped from $5 to $50, Production of metals used for corrosion resistance and to replace corroded parts require large amounts of energy, thus compounding the nation’s energy problems. ‘The most comprehensive study of the annual cost of metallic corrosion in the United States was conducted by the National Bureau of Standards (NBS) and Battelle Memorial Institute in response to congressional directive. Results are published in a seven-part series. The first is, “NBS- Battelle Cost of Corrosion Study ($70 Billion) Part 1—Introduction,”” by J. H. Payer, W. K. Boyd, D. B. Dippold, and W. H. Fisher of Battelle (Materials Performance, May 1980). The other six parts appeared in sub- sequent issues of Materials Performance (June-November 1980). The figure of $70 billion* covers corrosion (in 1975) of metals (nonmetallics not included) and are costs incurred if corrosion did not exist; this amount has ‘no practical significance, but it does emphasize the magnitude of the problem. Unfortunately, $70 billion has been simply stated as the “cost of corrosion” in later literature and is misteading (implying that $70 billion could be saved) because nothing can be done economically to reduce most of these costs. It is somewhat like asking how much you could save on your food budget if you stopped eating. However, the report states that about $10 billion could be saved if best, and presently known, practices to combat ‘The USS. Depariment of Commerce stated, “Corrosion wil cot the Unite States an ‘timated 126 billion dlls in 1982." (Materials Performance, 87, Feb. 1983).rerropucnon 3 corrosion were applied. Chemical industry efforts involve high costs, but this industry is in the forefront with regard to utilizing corrosion control practices. In fact our economy would be drastically changed if there were no corrosion. For example, automobiles, ships, underground pipelines. and household appliances would not require coatings. The stainless stel industry would essentially disappear and copper would be used only for electrical Purposes. Most metallic plants, as well as consumer products, would be made of steel or cast iron. Although corrosion is inevitable, its cost can be considerably reduced, For example, an inexpensive magnesium anode could double the life of a domestic hot water tank. Washing a car to remove road deicing salts is helpful. Proper selection of materials and good design reduce costs of corrosion. A good maintenance painting program pays for itself many times over. Here is where the corrosion engineer enters the picture and is effective his or her primary function is to combat corrosion Aside from its direct costs in dollars, corrosion is a serious problem because it definitely contributes to the depletion of our natural resources, For example, steel is made from iron ore, and our domestic supply of high grade directly smeltable iron ore has dwindled. Another important factor ‘concerns the world’s supply of metal resources. The rapid industrialization ‘of many countries indicates that the competition for and the price of metal resources will increase. The United States is no longer the chief consumer of ‘mineral resourees, 1-2 Corrosion Engineering Corrosion engineering is the application of science and art to prevent or control corrosion damage economically and safely. Inorder to perform ther function propely, corrosion engineers must be well versed in the practices and principles of corrosion: the chemical ‘metallurgical, physical, and mechanical properties of materials: corrosion testing: the nature ofeorrosive environments; the availabilty and fabrication of materials: computers*; and design. They also must have the usual attributes of engineers—a’sense of human relations, integrity, the ability to think and analyze, an awareness of the importance of safety, common sense, a sense of organization, and, of prime importance, a solid feeling for ‘economics. In solving corrosion problems, the corrosion engineer must select the method that will maximize profits. One definition of economics is simply—“there is no free lunch” The following articles offer insight into applications of computer ‘See Chapter 4 for the revolution brought about by the intradection of eesronie insicumentaion in corrosion scence and engineering