Handbook of cathodic corrosion protection: theory and practice of electrochemical protection processes

601 Pages·1997·14.75 MB·English

by  Walter von Baeckmann, Wilhelm Schwenk, Werner Prinz

Handbook of
CATHODIC
CORROSION
PROTECTION
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With contributions from:
W. von Baeckmann, H. Bohnes, G. Franke, D. Funk, C. Gey, H. Grafen,
G. Heim, V. Heinzelmann, K. Horras, B. Isecke, H. Kampermann, B. Leutner,
H. -U. Paul, F. Paulekat, W. Prinz, B. Richter, G. Rieger, H. G. Schoneich, W. Schwenk
J_ Gulf Professional Publishing
H an imprint of Elsevier Science
Gulf Professional Publishing is an imprint of Elsevier Science.
Copyright © 1997 by Elsevier Science (USA).
All rights reserved.
Originally published by Gulf Publishing Company, Houston, TX.
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Printed in the United States of America.
Contents
Foreword to the Third Edition xix
Foreword to the First Edition xx
Preface xxii
Acknowledgments xxiii
Index of Authors xxiv
Commonly Used Quantities, Constants, and Symbols xxv
Frequently Used Indices xxx
Chemical and Thermodynamic Quantities Y xxx
Electrochemical Quantities Y xxx
Electrical Quantities Y xxx
General Symbols xxx
American and European Electrical Cable Sizes xxxii
1 The History of Corrosion Protection 1
W. v. BAECKMANN
1.1 Corrosion Protection for Buried Pipelines 1
1.2 Corrosion Protection by Painting 8
1.3 History of Cathodic Protection 9
1.4 Development of Stray Current Protection 20
1.5 Corrosion Protection by Information 23
1.6 References 25
2 Fundamentals and Concepts of Corrosion and
Electrochemical Corrosion Protection 27
W. SCHWENK
2.1 Corrosion Processes, Corrosion Damage, and Protective
Countermeasures 27
2.2 Electrochemical Corrosion 29
2.2.1 Metallic Materials 30
v
2.2.2 Aqueous Electrolytes 34
2.2.3 Electrochemical Phase Boundary Reactions 36
2.2.3.1 Basic Thermodynamics 37
2.2.3.2 Electrochemical Kinetics 40
2.2.4 Mixed Electrodes 44
2.2.4.1 Homogeneous Mixed Electrodes 44
2.2.4.2 Heterogeneous Mixed Electrodes and Cell Formation 46
2.2.5 Observations of Current Distribution 50
2.3 Potential Dependence of Corrosion Extent 52
2.3.1 Almost Uniform Weight Loss Corrosion 53
2.3.1.1 Weight Loss Corrosion of Active Metals 53
2.3.1.2 Weight Loss Corrosion of Passive Metals 59
2.3.2 Pitting Corrosion 62
2.3.3 Stress Corrosion 63
2.3.4 Hydrogen-Induced Corrosion 66
2.3.5 Corrosion Fatigue 70
2.3.6 Limits of Applicability of Electrochemical Protection Processes 70
2.4 Critical Protection Potentials and Ranges 71
2.5 References 76
3 Fundamentals and Practice of Electrical Measurements ... 79
W. v. BAECKMANN AND W. SCHWENK
3.1 The Electrical Parameters: Current, Voltage, and Resistance 79
3.2 Reference Electrodes 85
3.3 Potential Measurement 88
3.3.1 Bases of Potential Measurement of Electrodes with Flowing
Current 88
3.3.2 Application of Potential Measurement 96
3.3.2.1 Measuring Instruments and Their Properties 96
3.3.2.2 Potential Measurements on Pipelines and Storage Tanks 97
3.3.2.3 Potential Measurement under the Influence of Stray Currents 100
3.3.2.4 Potential Measurement under the Influence of Alternating
Currents 102
3.3.3 Application'of Protection Criteria 103
3.3.3.1 Pragmatic Protection Criteria for Nonalloyed Ferrous Materials ... 104
3.3.3.2 Potential Measurement with Potential Test Probes 106
3.4 Current Measurement 107
3.4.1 General Advice for Measurement of Current 107
3.4.2 Pipe Current Measurement 108
vi
3.4.3 Measurement of Current Density and Coating Resistance 110
3.5 Resistivity Measurement 112
3.5.1 Resistivity Measuring Instruments 113
3.5.2 Measurement of Specific Soil Resistivity 114
3.5.3 Measurement of Grounding Resistance 118
3.6 Location of Faults 119
3.6.1 Measurement of Foreign Contacts 120
3.6.1.1 Fault Location using dc 120
3.6.1.2 Fault Location with ac 122
3.6.2 Location of Heterogeneous Surface Areas by Measurements
of Field Strength 123
3.6.2.1 Location of Local Anodes 124
3.6.2.2 Location of Coating Defects 125
(a) Circular damage 127
(b) Porous coating 129
3.7 Intensive Measurement Technique 131
3.7.1 Quantities to be Measured and Objectives of Intensive
Measurement Technique 132
3.7.2 Carrying Out an Intensive Measurement 135
(a) Determination of the pipe/soil potential 135
(b) Determination of AU values 136
3.8 References 137
4 Corrosion in Aqueous Solutions and Soil 139
G. HEIM AND W. SCHWENK
4.1 Action of Corrosion Products and Types of Corrosion 139
4.2 Determining the Corrosion Likelihood of Uncoated Metals 142
4.2.1 Corrosion in Soils 144
4.2.2 Corrosion in Aqueous Media 148
4.3 Enhancement of Anodic Corrosion by Cell Formation
or Stray Currents from dc Installations 148
4.4 Corrosion Due to ac Interference 150
4.5 References 152
5 Coatings for Corrosion Protection 153
G. HEIM AND W. SCHWENK
5.1 Objectives and Types of Corrosion Protection by Coatings 153
5.1.1 Organic Coatings 153
vii
5.1.2 Cement Mortar Coatings 154
5.1.3 Enamel Coatings 154
5.1.4 Metallic Coatings 154
5.2 Properties of Organic Coatings 155
5.2.1 Electrical and Electrochemical Properties 155
5.2.1.1 Review of the Types of Reactions 155
5.2.1.2 Coating Resistance and Protection Current Demand 156
5.2.1.3 Effectiveness of Cathodes and Cell Formation 162
5.2.1.4 Electrochemical Blistering 163
5.2.1.5 Cathodic Disbonding 166
5.2.2 Physicochemical Properties 169
5.2.3 Mechanical Properties 170
5.2.4 Corrosion of the Steel under the Coating 171
5.3 Properties of Cement Mortar and Concrete 173
5.3.1 Corrosion of Mortar 173
5.3.2 Corrosion of Steel in Mortar 174
5.4 Properties of Enamel Coatings 175
5.5 Properties of Metallic Coatings 176
5.6 References 177
6 Galvanic (Sacrificial) Anodes 179
H. BOHNES AND G. FRANKE
6.1 General Information 179
6.1.1 Current Capacity of Galvanic Anodes 180
6.1.2 Current Discharge from Galvanic Anodes 183
6.2 Anode Materials 185
6.2.1 Iron 185
6.2.2 Zinc 185
6.2.3 Aluminum 188
6.2.4 Magnesium 191
6.3 Backfill Materials 196
6.4 Supports 198
6.5 Forms of Anodes 199
6.5.1 Rod Anodes 200
6.5.2 Plates and Compact Anodes 200
6.5.3 Anodes for Tanks 201
6.5.4 Offshore Anodes 202
6.5.5 Special Forms 202
6.6 Quality Control and Performance Testing 203
Vlll
6.7 Advantages and Disadvantages of Galvanic Anodes 204
6.8 References 206
7 Impressed Current Anodes 207
H. BOHNES AND D. FUNK
7.1 General Comments 207
7.2 Anode Materials 208
7.2.1 Solid Anodes 208
7.2.2 Noble Metals and Valve Metals Coated with Noble Metals 213
7.2.3 Metal Oxide-Coated Valve Metals 216
7.2.4 Polymer Cable Anodes 217
7.3 Insulating Materials 217
7.4 Cables 218
7.5 Forms of Anode 219
7.5.1 Anodes Suitable for Soil 219
7.5.2 Anodes Suitable for Water 221
7.5.3 Anodes for Internal Application 222
7.6 References 224
8 Impressed Current Equipment and Transformer-
Rectifiers 225
W. v. BAECKMANN AND H. KAMPERMAN
8.1 Site and Electrical Protection Measures 226
8.2 Design and Circuitry of Impressed Current 228
8.3 Rectifier Circuit 229
8.4 Adjustable Transformer-Rectifiers 230
8.5 Rectifiers Resistant to High Voltage 232
8.6 Control Rectifiers 233
8.7 Transformer-Rectifiers without Mains Connections 237
8.8 Equipment and Control of Transformer-Rectifiers 237
8.9 References 242
9 Impressed Current Ground Beds and Interference
Problems 243
W. VON BAECKMANN AND W. PRINZ
9.1 Impressed Current Ground Beds 244
9.1.1 Continuous Horizontal Anode Beds 244
IX