Advances in Corrosion Science and Technology PDF
Preview Advances in Corrosion Science and Technology
ADVANCES IN CORROSION SCIENCE AND TECHNOLOGY VOLUME 2 ADVANCES IN CORROSION SCIENCE AND TECHNOLOGY Editors: M. G. Fontana and R. W. Staehle Corrosion Center, Department of Metallurgical Engineering The Ohio State University, Columbus, Ohio Editorial Board: VITIORIO CARASSITI JEROME KRUGER Universita di Ferrara National Bureau of Standards Ferrara, Italy Washington, D. C. MORRIS COHEN National Research Council PAUL LACOMBE Ottawa, Ontario, Canada L'Ecole National Superieure des Mines de Paris JOSEPH E. DRALEY Paris, France Argonne National Laboratory Argonne, Illinois MARCEL POURBAIX HELLMUTH FISCHER CEBELCOR Technische Hochschule Karlsruhe Brussels, Belgium Karlsruhe, Germany T. P. HOAR SAKAE TAJIMA University of Cambridge Tokyo City University Cambridge, England Tokyo, Japan Volume 1 (1970) - Contributors V. CARASSITI S. TAJIMA DUDLEY DE G. JONES G. TRABANELLI R. M. LATANISION A. R. C. WESTWOOD H. G. MASTERSON Volume 2 (1972) - Contributors P. C. S. HAYFIELD W. P. IVERSON M. D. HYATI M. O. SPEIDEL ADVANCES IN CORROSION SCIENCE AND TECHNOLOGY VOLUME 2 Edited by Mars G. Fontana and Roger W. Staehle ~PLENU. PRESS· NEWYORI-LONDON· 1912 Library of Congress Catalog Card Number 76-107531 ISBN-13: 978-1-4615-8257-1 e-ISBN-13: 978-1-4615-8255-7 001: 10.1007/978-1-4615-8255-7 @ 1972 Plenum Press, New York Softcover reprint of the hardcover 1st edition 1972 A Division of Plenum Publishing Corporation 227 West 17th Street, New York, N.Y. 10011 United Kingdom edition published by Plenum Press, London A Division of Plenum Publishing Company, Ltd. Davis House (4th Floor), 8 Scrubs Lane, Harlesden, London, NW 10, 6SE, England All rights reserved No part of this publication may be reproduced in any form without written permission from the publisher PREFACE TO VOLUME 1 This series was organized to provide a forum for review papers in the area of corrosion. The aim of these reviews is to bring certain areas of corrosion science and technology into a sharp focus. The volumes of this series will be published approximately on a yeady basis and will each contain three to five reviews. The articles in each volume will be selected in such a way to be of interest both to the corrosion scientists and the corrosion tech nologists. There is, in fact, a particular aim in juxtaposing these interests because of the importance of mutual interaction and interdisciplinarity so important in corrosion studies. It is hoped that the corrosion scientists in this way may stay abreast of the activities in corrosion technology and vice versa. In this series the term "corrosion" will be used in its very broadest sense. This will include, therefore, not only the degradation of metals in aqueous environment but also what is commonly referred to as "high temperature oxidation." Further, the plan is to be even more general than these topics; the series will include all solids and all environments. Today, engineering solids include not only metals but glasses, ionic solids, polymeric solids, and composites of these. Environments of interest must be extended to liquid metals, a wide variety of gases, nonaqueous electrolytes, and other nonaqueous liquids. Furthermore, there are certain complex situations such as wear, cavitation, fretting, and other forms of degradation which it is appropriate to include. At suitable intervals certain of the review articles will be updated as the demands of technology and the fund of new informa tion dictate. Another important aim of this series is to attract those in areas pe ripheral to the field of corrosion. Thus, physicists, physical metallurgists, physical chemists, and electronic scientists all can make very substantial contributions to the resolution of corrosion problems. It is hoped that these reviews will make the field more accessible to potential contributors from these other areas. Many of the phenomena in corrosion are so complex v vi Preface to Volume 1 that it is impossible for reasonable progress to be made without more serious and enthusiastic interdisciplinary interest. In addition to the discussion of scientific and technological phenomena the articles will also include discussions of important techniques which should be of interest to corrosion scientists. R. W. STAEHLE M. G. FONTANA Columbus, Ohio CONTENTS Chapter 1 Biological Corrosion w. P. Iverson Introduction. . . . 1 Organisms 4 Microorganisms 5 Fungi. . 5 Bacteria. . 8 Algae. . . 16 Macroorganisms 16 Mechanisms of Biological Corrosion . 17 Production of Oxidizing Agents 18 Acids (Hydrogen Ions) . 18 Sulfur Compounds. . . . 19 Other Agents . . . . . . 22 Production of Differential Oxygen and Chemical Concentration Cells . . . . . . . . . . . 23 Cathodic Depolarization . . . . . 25 Disruption of Protective Films . . 33 Breakdown of Corrosion Inhibitors 34 Other Mechanisms. . . . . . 34 Combinations of Mechanisms . 34 Prevention of Biological Corrosion. 35 Selection of Environment. . 35 Modification of Environment 35 Microbial Inhibitors 35 Protective Coating . 36 Cathodic Protection 36 References 36 vii viii Contents Chapter 2 Ellipsometry in Corrosion Technology Peter Hayfield Introduction. . . . . . . . . . . . . . . 43 Optical Properties of Metals and Dielectrics 45 Reflection from a Film-Free Surface .... 49 Reflection from a Film-Covered Surface . . 56 Measurement of Elliptically Polarized Light 58 Compensator Methods 59 Intensity Methods . . 65 Computational Techniques 68 Graphical Methods 71 Reflectivity Measurements 76 Determination of Film Optical Properties 78 The Liquid Immersion Method 78 Becke Test ....... . 80 Interferometry . . . . . . . 81 The Brewster Angle Method 81 Calculation . . . . . . . . 82 Measurements on Films Less Than 50 A in Thickness 82 Reflection from Anisotropic Media . . . . . . 84 Reflection from Films of Nonuniform Thickness 84 Reflection from Surfaces of Varying Roughness 85 Instrumentation . . . . . . . . . . . . . 87 Alignment and Calibration of Ellipsometers 88 Applications to Corrosion Studies 90 Bare Metal Surfaces .. 91 Adsorption Phenomena. . . 93 Passivity ......... . 95 Electropolishing and Anodic Oxidation 99 Anodic Protection . . . . 101 Electrochemical Machining . 102 Cathodic Reactions . . . . 102 Natural Corrosion Reactions 102 Aqueous Reactions 102 Outdoor Exposure . . . 105 Influence of Films on Mechanical Properties (Including Stress Corrosion and Corrosion Fatigue). . . . 106 Contents ix Gaseous Oxidation . 106 Conclusions 108 References 109 Chapter 3 Stress-Corrosion Cracking of High-Strength Aluminum Alloys M. O. Speidel and M. V. Hyatt Introduction. . . . . . . . . . . . . 115 Mechanical Aspects (The Effects of Stress) . 126 Grain Shape and Orientation 126 The Sources of Stress . . . 128 Intergranular Corrosion 131 Exfoliation Corrosion 132 Smooth-Specimen Test Techniques. 132 Precracked-Specimen Test Techniques 138 Crack Velocity As a Function of Stress Intensity. 139 Relationship between Data from Smooth and Precracked Speci- mens. . . . . . . . . . . . . . . . . . . . . . . 147 Experimental Difficulties in Testing Precracked Specimens 150 Residual Stresses .......... 150 Corrosion-Product Wedging. . . . . . 153 Specimen Orientation and Grain Flow. . 153 Crack Branching. . 153 Delamination . . . . . . . 157 Short Testing Times . . . . 157 Relating Laboratory Data to Crack Growth in Service 158 Advantages of Precracked Specimens for SCC Testing 158 Some Advantages of Smooth-SCC Specimens. . . . . . 159 Some Specific Applications of Precracked-Specimen Data 159 Effects of Environment. . 161 Gaseous Environments 163 Hydrogen Gas. 163 Argon. . 165 Nitrogen . . 169 Air. . . . . 169 Outdoor Exposure 171 Aqueous Solutions 175 Distilled Water 175 x Contents Neutral Aqueous Salt Solutions . . . . . . . . . . .. 177 Aqueous Solutions Containing Chloride, Bromide, and Iodide Ions . . . . . 177 Effect of Electrical Potential 186 Effect of pH . . . . . . . 190 Effect of Temperature . . . 193 Effect of Solution Viscosity . 199 Acids. . . . . . . 199 Nitrogen Tetroxide. 202 Organic Liquids . . 204 Liquid Metals . . . 209 Metallurgical Aspects and Alloy Development 210 Aluminum-Magnesium Alloys (5000 Series). 210 Temper Designations. . . . . . . . . 212 Relationship between Microstructure and SCC 212 SCC and Exfoliation Corrosion in Commercial Aluminum- Magnesium Alloys . . . . . . . . . . . . 217 5000-Series Alloy Development . . . . . . . . 220 Aluminum-Magnesium-Silicon Alloys (6000 Series) . 223 Aluminum-Copper-Magnesium Alloys (2000 Series) . 224 Physical Metallurgy . . . . . . . . . . 225 Susceptibility to Stress-Corrosion Cracking . 231 Effects of Quench Rate ......... 233 Effects of Artificial Aging . . . . . . . . 237 Rapid Tests for Determining Susceptibility to Intergranular Attack and SCC Resistance ...... '. . . . . . 241 Aluminum-Zinc-Magnesium and Aluminum-Zinc-Magnesium- Copper Alloys (7000 Series). . . . . . . . 244 Physical Metallurgy . . . . . . . . . . 245 Susceptibility to Stress-Corrosion Cracking 250 Effects of Quench Rate 252 Effects of Overaging . . 255 Silver Additions . . . . 262 New Alloy Development 264 Comparison of the Various Thick-Section Alloys with Commercially Available Alloys 269 Thermomechanical Processing 277 New Fabrication Techniques 278 New Sheet Alloys 279 Weldable Alloys. . . . . . . . 280
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