Corrosion engineering : principles and practice

770 Pages·2008·14.807 MB·English

by  Pierre R Roberge

Corrosion Engineering
Principles and Practice
Pierre R. Roberge, Ph.D., P.Eng.
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DOI: 10.1036/0071482431
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Contents
Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xiii
1 The Study of Corrosion . . . . . . . . . . . . . . . . . . . . . . . 1
1.1 Why Study Corrosion? . . . . . . . . . . . . . . . . . . . . 1
1.2 The Study of Corrosion . . . . . . . . . . . . . . . . . . . . 2
1.3 Needs for Corrosion Education . . . . . . . . . . . . . 5
1.4 The Functions and Roles of
a Corrosion Engineer . . . . . . . . . . . . . . . . . . . . . 8
1.5 The Corrosion Engineer’s Education . . . . . . . . 11
1.6 Strategic Impact and Cost of
Corrosion Damage . . . . . . . . . . . . . . . . . . . . . . . 13
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
2 Corrosion Basics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
2.1 Why Metals Corrode . . . . . . . . . . . . . . . . . . . . . . 19
2.2 Matter Building Blocks . . . . . . . . . . . . . . . . . . . . 22
2.3 Acidity and Alkalinity (pH) . . . . . . . . . . . . . . . . 28
2.4 Corrosion as a Chemical Reaction . . . . . . . . . . 31
2.4.1 Corrosion in Acids . . . . . . . . . . . . . . . . 31
2.4.2 Corrosion in Neutral and
Alkaline Solutions . . . . . . . . . . . . . . . . 32
Reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
3 Corrosion Electrochemistry . . . . . . . . . . . . . . . . . . . . 35
3.1 Electrochemical Reactions . . . . . . . . . . . . . . . . . 35
3.2 Anodic Processes . . . . . . . . . . . . . . . . . . . . . . . . . 38
3.3 Faraday’s Law . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
3.4 Cathodic Processes . . . . . . . . . . . . . . . . . . . . . . . 40
3.5 Surface Area Effect . . . . . . . . . . . . . . . . . . . . . . . 45
Reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
4 Corrosion Thermodynamics . . . . . . . . . . . . . . . . . . . 49
4.1 Free Energy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
4.2 Standard Electrode Potentials . . . . . . . . . . . . . . 51
4.3 Nernst Equation . . . . . . . . . . . . . . . . . . . . . . . . . . 54
4.4 Thermodynamic Calculations . . . . . . . . . . . . . . 55
4.4.1 The Aluminum-Air Power Source . . . 55
4.4.2 Detailed Calculations . . . . . . . . . . . . . . 59
4.4.3 Reference Electrodes . . . . . . . . . . . . . . 62
iii
iv Contents Contents v
4.5 Reference Half-Cells (Electrodes) . . . . . . . . . . . 62
4.5.1 Conversion between References . . . . . 66
4.5.2 Silver/Silver Chloride
Reference Electrode . . . . . . . . . . . . . . . 66
4.5.3 Copper/Copper Sulfate
Reference Electrode . . . . . . . . . . . . . . . 68
4.6 Measuring the Corrosion Potential . . . . . . . . . . 71
4.7 Measuring pH . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
4.7.1 Glass Electrodes . . . . . . . . . . . . . . . . . . 73
4.7.2 Antimony Electrode . . . . . . . . . . . . . . 74
4.8 Potential-pH Diagram . . . . . . . . . . . . . . . . . . . . 74
4.8.1 E-pH Diagram of Water . . . . . . . . . . . . 75
4.8.2 E-pH Diagrams of Metals . . . . . . . . . . 76
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84
5 Corrosion Kinetics and Applications
of Electrochemistry to Corrosion . . . . . . . . . . . . . 85
5.1 What Is Overpotential? . . . . . . . . . . . . . . . . . . . . 85
5.2 Activation Polarization . . . . . . . . . . . . . . . . . . . . 86
5.3 Concentration Polarization . . . . . . . . . . . . . . . . 90
5.4 Ohmic Drop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94
5.4.1 Water Resistivity Measurements . . . . 94
5.4.2 Soil Resistivity Measurements . . . . . . 97
5.5 Graphical Presentation of Kinetic Data
(Evans Diagrams) . . . . . . . . . . . . . . . . . . . . . . . . 103
5.5.1 Activation Controlled Processes . . . . . 103
5.5.2 Concentration Controlled
Processes . . . . . . . . . . . . . . . . . . . . . . . . 104
5.6 Examples of Applied Electrochemistry
to Corrosion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107
5.6.1 Electrochemical Polarization
Corrosion Testing . . . . . . . . . . . . . . . . . 107
5.6.2 Corrosion Monitoring . . . . . . . . . . . . . 121
5.6.3 Cathodic Protection . . . . . . . . . . . . . . . 134
5.6.4 Anodic Protection . . . . . . . . . . . . . . . . . 135
5.6.5 Aluminum Anodizing . . . . . . . . . . . . . 137
5.6.6 Chloride Extraction . . . . . . . . . . . . . . . 142
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144
6 Recognizing the Forms of Corrosion . . . . . . . . . . . . 147
6.1 Recognizing Corrosion . . . . . . . . . . . . . . . . . . . . 147
6.2 General or Uniform Attack . . . . . . . . . . . . . . . . 151
6.3 Localized Corrosion . . . . . . . . . . . . . . . . . . . . . . 155
6.3.1 Pitting Corrosion . . . . . . . . . . . . . . . . . 155
6.3.2 Crevice Corrosion . . . . . . . . . . . . . . . . . 164
iv Contents Contents v
6.3.3 Galvanic Corrosion . . . . . . . . . . . . . . . 175
6.3.4 Intergranular Corrosion . . . . . . . . . . . . 180
6.3.5 Dealloying . . . . . . . . . . . . . . . . . . . . . . . 181
6.3.6 Hydrogen-Induced Cracking . . . . . . . 183
6.3.7 Hydrogen Blistering . . . . . . . . . . . . . . . 184
6.4 Velocity Induced Corrosion . . . . . . . . . . . . . . . . 185
6.4.1 Erosion–Corrosion . . . . . . . . . . . . . . . . 188
6.4.2 Cavitation . . . . . . . . . . . . . . . . . . . . . . . 192
6.5 Mechanically Assisted Corrosion . . . . . . . . . . . 194
6.5.1 Stress Corrosion Cracking . . . . . . . . . . 197
6.5.2 Corrosion Fatigue . . . . . . . . . . . . . . . . . 201
6.5.3 Fretting Corrosion . . . . . . . . . . . . . . . . 203
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205
7 Corrosion Failures, Factors, and Cells . . . . . . . . . . . 207
7.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 207
7.2 Information to Look For . . . . . . . . . . . . . . . . . . . 209
7.2.1 Temperature Effects . . . . . . . . . . . . . . . 209
7.2.2 Fluid Velocity Effects . . . . . . . . . . . . . . 210
7.2.3 Impurities in the Environment . . . . . . 211
7.2.4 Presence of Microbes . . . . . . . . . . . . . . 213
7.2.5 Presence of Stray Currents . . . . . . . . . 213
7.3 Identifying the Corrosion Factors . . . . . . . . . . . 216
7.4 Examples of Corrosion Cells . . . . . . . . . . . . . . . 224
7.4.1 Galvanic Cells . . . . . . . . . . . . . . . . . . . . 227
7.4.2 Concentration Cells . . . . . . . . . . . . . . . 231
7.4.3 Differential Aeration:
Oxygen Concentration Cells . . . . . . . . 233
7.4.4 Temperature Cells . . . . . . . . . . . . . . . . . 235
7.4.5 Stray Current Cells . . . . . . . . . . . . . . . . 237
7.4.6 Stress Cells . . . . . . . . . . . . . . . . . . . . . . . 239
7.4.7 Surface Film Cells . . . . . . . . . . . . . . . . . 243
7.4.8 Microbial Corrosion Cells . . . . . . . . . . 245
7.5 Corrosion Avoidance . . . . . . . . . . . . . . . . . . . . . . 246
7.5.1 Pitting Mitigation . . . . . . . . . . . . . . . . . 247
7.5.2 Crevice Corrosion Mitigation . . . . . . . 247
7.5.3 Galvanic Corrosion Mitigation . . . . . . 248
7.5.4 Fretting Corrosion Mitigation . . . . . . . 248
7.5.5 Mitigation of Stress
Corrosion Cracking . . . . . . . . . . . . . . . 248
7.6 Visualizing Corrosion Cells . . . . . . . . . . . . . . . . 250
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 254
vi Contents Contents vii
8 Corrosion by Water . . . . . . . . . . . . . . . . . . . . . . . . . . . 257
8.1 Importance of Water . . . . . . . . . . . . . . . . . . . . . . 257
8.2 Corrosion and Water Quality
and Availability . . . . . . . . . . . . . . . . . . . . . . . . . . 257
8.2.1 Corrosion Impact . . . . . . . . . . . . . . . . . 258
8.2.2 Corrosion Management . . . . . . . . . . . . 260
8.2.3 Condition Assessment
Techniques . . . . . . . . . . . . . . . . . . . . . . . 265
8.3 Types of Water . . . . . . . . . . . . . . . . . . . . . . . . . . . 268
8.3.1 Natural Waters . . . . . . . . . . . . . . . . . . . 268
8.3.2 Treated Waters . . . . . . . . . . . . . . . . . . . . 284
8.4 Cooling Water Systems . . . . . . . . . . . . . . . . . . . . 287
8.4.1 Once-Through Systems . . . . . . . . . . . . 287
8.4.2 Recirculated Systems . . . . . . . . . . . . . . 288
8.4.3 Heat Exchangers . . . . . . . . . . . . . . . . . . 291
8.5 Steam Generating Systems . . . . . . . . . . . . . . . . . 294
8.5.1 Treatment of Boiler
Feedwater Makeup . . . . . . . . . . . . . . . . 294
8.5.2 Fossil Fuel Steam Plants . . . . . . . . . . . 296
8.5.3 Supercritical Steam Plants . . . . . . . . . . 297
8.5.4 Waste Heat Boilers . . . . . . . . . . . . . . . . 298
8.5.5 Nuclear Boiling Water Reactors . . . . . 299
8.5.6 Nuclear Pressurized
Water Reactors . . . . . . . . . . . . . . . . . . . 300
8.5.7 Corrosion Costs
to the Power Industry . . . . . . . . . . . . . 302
8.6 Water Treatment . . . . . . . . . . . . . . . . . . . . . . . . . . 307
8.6.1 Corrosion Inhibitors . . . . . . . . . . . . . . . 309
8.6.2 Scale Control . . . . . . . . . . . . . . . . . . . . . 311
8.6.3 Microorganisms . . . . . . . . . . . . . . . . . . 311
8.7 Scaling Indices . . . . . . . . . . . . . . . . . . . . . . . . . . . 313
8.7.1 Langelier Saturation Index . . . . . . . . . 314
8.7.2 Other Indices . . . . . . . . . . . . . . . . . . . . . 316
8.8 Ion-Association Model . . . . . . . . . . . . . . . . . . . . 318
8.8.1 Limiting Halite Deposition in a
Wet High-Temperature Gas Well . . . . 320
8.8.2 Identifying Acceptable Operating Range
for Ozonated Cooling Systems . . . . . . 321
8.8.3 Optimizing Calcium Phosphate
Scale Inhibitor Dosage in a High-TDS
Cooling System . . . . . . . . . . . . . . . . . . 326
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 327
vi Contents Contents vii
9 Atmospheric Corrosion . . . . . . . . . . . . . . . . . . . . . . . 329
9.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 329
9.2 Types of Corrosive Atmospheres . . . . . . . . . . 330
9.2.1 Industrial . . . . . . . . . . . . . . . . . . . . . . . 330
9.2.2 Marine . . . . . . . . . . . . . . . . . . . . . . . . . 331
9.2.3 Rural . . . . . . . . . . . . . . . . . . . . . . . . . . . 331
9.2.4 Indoor . . . . . . . . . . . . . . . . . . . . . . . . . . 333
9.3 Factors Affecting Atmospheric Corrosion . . . 334
9.3.1 Relative Humidity
and Dew Point . . . . . . . . . . . . . . . . . . 338
9.3.2 Pollutants . . . . . . . . . . . . . . . . . . . . . . . 339
9.3.3 Deposition of Aerosol Particles . . . . 340
9.3.4 Deicing Salts . . . . . . . . . . . . . . . . . . . . 341
9.4 Measurement of Atmospheric
Corrosivity Factors . . . . . . . . . . . . . . . . . . . . . . 349
9.4.1 Time of Wetness . . . . . . . . . . . . . . . . . 349
9.4.2 Sulfur Dioxide . . . . . . . . . . . . . . . . . . . 350
9.4.3 Airborne Chlorides . . . . . . . . . . . . . . . 350
9.4.4 Atmospheric Corrosivity . . . . . . . . . . 353
9.5 Atmospheric Corrosivity
Classification Schemes . . . . . . . . . . . . . . . . . . . 358
9.5.1 Environmental Severity Index . . . . . 358
9.5.2 ISO Classification of Corrosivity
of Atmospheres . . . . . . . . . . . . . . . . . . 362
9.5.3 Maps of Atmospheric Corrosivity . . . 362
9.6 Atmospheric Corrosion Tests . . . . . . . . . . . . . . 366
9.7 Corrosion Behavior and Resistance . . . . . . . . 370
9.7.1 Iron, Steel, and Stainless Steel . . . . . . 370
9.7.2 Copper and Copper Alloys . . . . . . . . 375
9.7.3 Nickel and Nickel Alloys . . . . . . . . . . 376
9.7.4 Aluminum and Aluminum Alloys . . . 377
9.7.5 Zinc and Zinc Alloys . . . . . . . . . . . . . 379
9.7.6 Polymeric Materials . . . . . . . . . . . . . . 381
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 383
10 Corrosion in Soils and Microbiologically
Influenced Corrosion . . . . . . . . . . . . . . . . . . . . . . . 385
10.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 385
10.2 Corrosion in Soils . . . . . . . . . . . . . . . . . . . . . . . 385
10.2.1 Soil Classification . . . . . . . . . . . . . . . . 387
10.2.2 Soil Parameters
Affecting Corrosivity . . . . . . . . . . . . . 389
10.2.3 Soil Corrosivity Classifications . . . . . 391
10.2.4 Auxiliary Effects
of Corrosion Cells . . . . . . . . . . . . . . . . 394
viii Contents Contents ix
10.2.5 Examples of Buried Systems . . . . . . . 398
10.2.6 Corrosion of Materials
Other Than Steel . . . . . . . . . . . . . . . . . 403
10.3 Microbiologically Influenced Corrosion . . . . 407
10.3.1 Planktonic or Sessile . . . . . . . . . . . . . . 409
10.3.2 Microbes Classification . . . . . . . . . . . 411
10.3.3 Monitoring Microbiologically
Influenced Corrosion . . . . . . . . . . . . . 416
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 428
11 Materials Selection, Testing,
and Design Considerations . . . . . . . . . . . . . . . . . . 431
11.1 Materials Selection . . . . . . . . . . . . . . . . . . . . . . . 431
11.2 Complexity of Corrosion Conscious
Materials Selection . . . . . . . . . . . . . . . . . . . . . . 433
11.2.1 Multiple Forms of Corrosion . . . . . . 433
11.2.2 Multiple Material/
Environment Combinations . . . . . . . 434
11.2.3 Precision of Corrosion Data . . . . . . . 437
11.2.4 Complexity of Materials/
Performance Interactions . . . . . . . . . 438
11.3 Selection Compromises . . . . . . . . . . . . . . . . . . . 440
11.3.1 Life-Cycle Costing . . . . . . . . . . . . . . . 441
11.3.2 Condition Assessment . . . . . . . . . . . . 443
11.3.3 Prioritization . . . . . . . . . . . . . . . . . . . . 445
11.4 Materials Selection Road Map . . . . . . . . . . . . . 445
11.4.1 Identify Initial Slate
of Candidate Materials . . . . . . . . . . . 446
11.4.2 Screen Materials Based
on Past Experience . . . . . . . . . . . . . . . 447
11.4.3 Conduct Environmental
Assessment . . . . . . . . . . . . . . . . . . . . . 447
11.4.4 Evaluate Materials Based on Potential
Corrosion Failure Modes . . . . . . . . . . 450
11.4.5 Select Corrosion Prevention
and Control Methods . . . . . . . . . . . . . 451
11.5 Design Considerations . . . . . . . . . . . . . . . . . . . 451
11.5.1 Designing Adequate Drainage . . . . . 454
11.5.2 Adequate Joining
and Attachments . . . . . . . . . . . . . . . . . 459
11.6 Testing Considerations . . . . . . . . . . . . . . . . . . . 463
11.6.1 Test Objectives . . . . . . . . . . . . . . . . . . . 463
11.6.2 Test Standards . . . . . . . . . . . . . . . . . . . 464
11.6.3 Cabinet Testing . . . . . . . . . . . . . . . . . . 471
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 474