Corrosion Resistance of Aluminum and Magnesium Alloys: Understanding, Performance, and Testing

Corrosion Resistance of Aluminum and Magnesium Alloys......Page 6
Contents......Page 10
Preface......Page 22
Acknowledgments......Page 24
Part One Electrochemical Fundamentals and Active–Passive Corrosion Behaviors......Page 26
A. Thermodynamic Considerations of Corrosion......Page 28
1.1. Electrolytic Conductance......Page 29
1.1.1. Faraday Laws......Page 30
1.2. Tendency to Corrosion......Page 31
1.3. The Electrochemical Interface......Page 32
1.3.1. Electric Double Layer......Page 33
1.4. Nernst Equation......Page 34
1.5.1. Standard States in Solution......Page 37
1.5.3. Positive and Negative Signs of Potentials......Page 38
1.6.1. Constant and Degree of Dissociation......Page 39
1.6.2. Activity and Concentration......Page 41
1.6.3. Theory of More Concentrated Solutions......Page 42
1.7. Mobility of Ions......Page 44
1.7.1. Law of Additivity of Kohlrausch......Page 45
1.7.2. Ion Transport Number or Index......Page 46
1.8. Conductance......Page 48
1.10. Gas Electrodes......Page 49
1.11.1. Alloyed Electrodes......Page 50
1.12.1. Metal–Insoluble Salt Electrodes......Page 51
1.12.2. Metal–Insoluble Oxide Electrodes......Page 52
1.13. Electrodes of Oxidation–Reduction......Page 53
1.14.1. Glass Electrodes......Page 54
1.14.2. Copper Ion-Selective Electrodes......Page 55
1.15.1. Chemical Cell with Transport......Page 56
1.15.2. Chemical Cell Without Transport......Page 58
1.16. Concentration Cells......Page 59
1.16.1. Concentration Cell with Difference of Activity at the Electrode and Electrolyte......Page 60
1.16.2. Junction Potential......Page 62
1.17.2. Displacement Cell......Page 66
1.17.3. Complexing Agent Cells......Page 67
1.19. Overlapping of Different Corrosion Cells......Page 68
1.20. Definition and Description of Corrosion......Page 69
1.21. Electrochemical and Chemical Reactions......Page 70
1.21.1. Electrochemical Corrosion......Page 71
1.21.2. Film-Free Chemical Interactions......Page 72
References......Page 73
2.1.1. Description......Page 74
2.1.2. Types of Corrosion......Page 75
2.1.3. Atmospheric Contaminants......Page 76
2.2. Aqueous Environments......Page 78
2.3. Organic Solvent Properties......Page 80
2.4. Underground Media......Page 81
2.5. Water Media Properties......Page 82
2.5.1. Water Composition......Page 83
2.5.2. The Oxidizing Power of Solution......Page 86
2.5.3. Scale Formation and Water Indexes......Page 87
2.6.1. Description......Page 90
2.6.2. The Pilling–Bedworth Ratio (PBR)......Page 91
2.6.3. Kinetics of Formation......Page 95
2.6.4. Corrosion Behaviors of Some Alloys at Elevated Temperatures......Page 97
References......Page 101
Overview......Page 103
3.1.1. Construction of Pourbaix Diagrams......Page 104
3.1.2. Predictions of E–pH Diagrams......Page 106
3.1.3. Utility and Limits of Pourbaix Diagrams......Page 108
3.2.2. Overpotentials......Page 109
3.3.1. The Phenomenon of Passivation......Page 119
3.3.2. Passive Layers and Their Formation......Page 122
3.3.3. Breakdown of Passivity......Page 125
3.3.4. Electrochemical and Physical Techniques for Passive Film Studies......Page 126
3.4.1. The E–pH Diagram of Aluminum......Page 127
3.4.2. Active and Passive Behaviors......Page 130
3.4.3. Pitting Corrosion of Aluminum Alloy 5086......Page 133
3.5.1. E–pH Diagram of Magnesium......Page 135
3.5.2. Passive Mg Layers (Films)......Page 138
3.5.3. Passive Properties and Stability......Page 139
3.5.4. Temperature Influence in Aqueous Media......Page 141
3.5.5. Atmospheric and High-Temperature Oxidation......Page 142
References......Page 143
Part Two Performance and Corrosion Forms of Aluminum and Its Alloys......Page 146
Overview......Page 148
4.1. Physical and General Properties of Aluminum......Page 149
4.2. Cast Aluminum Alloys......Page 150
4.2.1. Designation of Cast Aluminum Alloys and Ingots......Page 151
4.2.2. Alloying Elements......Page 153
4.2.3. Cast Alloys Series......Page 154
4.3.1. Designation of Wrought Aluminum Alloys......Page 155
4.3.2. Alloying Elements......Page 156
4.3.3. Wrought Aluminum Alloys Series......Page 158
4.3.4. Description of the Wrought Alloys Series......Page 161
4.4.1. Aluminum Powders......Page 165
4.4.3. Aluminum Matrix Composites and P/M- MMCs......Page 167
4.4.4. Al MMC Particles and Formation......Page 172
B. Use of Aluminum and Aluminum Alloys......Page 176
4.5.1. Standard General Purpose Aluminum Alloys......Page 177
4.5.2. Some Specific Uses......Page 178
4.6.2. Automotive Sheet and Structural Alloys......Page 179
4.6.6. Electrical Conductor Alloys......Page 181
4.7. Resistance of Aluminum Alloys to Atmospheric Corrosion......Page 182
4.8. Factors Affecting Atmospheric Corrosion of Aluminum Alloys......Page 183
4.9. Water Corrosion......Page 185
4.10. Seawater......Page 186
4.12. Some Aggressive Media: Acid and Alkaline Solutions......Page 187
4.12.1. Acids......Page 189
4.12.2. Alkalis......Page 191
4.13. Dry and Aqueous Organic Compounds......Page 192
4.15. Mercury......Page 193
4.16.1. Performance of the Cast Series......Page 194
4.16.2. Performance of the Wrought Series......Page 196
4.17. Aluminum High-Temperature Corrosion......Page 197
References......Page 198
Overview......Page 201
5.2. Description......Page 202
5.4.2. Surface Pretreatment......Page 204
5.4.4. Aluminum Alloys and Resistance to General Corrosion......Page 205
5.6. Galvanic Series of Aluminum Alloys......Page 206
5.7.1. Cu–Al Galvanic Cell......Page 210
5.7.3. Galvanic Effect of a Coating......Page 211
5.8. Deposition Corrosion......Page 212
5.10. Prevention......Page 213
5.11. Basic Study of Al–Cu Galvanic Corrosion Cell......Page 214
C. Localized Corrosion......Page 215
5.12.2. Kinetics......Page 216
5.12.3. The Pitting Potential......Page 218
5.12.4. Mechanisms......Page 219
5.12.5. Possible Stages of Pitting......Page 220
5.12.6. Prevention of Pitting Corrosion......Page 226
5.12.7. Corrosion Resistance of Aluminum Cathodes......Page 227
5.13.1. General Considerations and Description......Page 228
5.13.2. Poultice Corrosion......Page 230
5.13.4. Water Stains on AA3xxx......Page 231
5.14.1. General Considerations......Page 233
5.14.2. Aluminum Alloys and Filiform Corrosion......Page 234
5.14.3. Kinetics, Mechanism, and Prevention......Page 235
5.14.4. Filiform Occurrence......Page 236
References......Page 237
Overview......Page 240
6.1. Fundamentals of METIC......Page 241
6.1.1. Influence of Metallurgical and Mechanical Treatments......Page 242
6.2.2. Intergranular Corrosion......Page 243
6.2.3. Exfoliation......Page 249
6.3.1. Corrosion Resistance of Brazed, Soldered, and Bonded Joints......Page 256
6.3.2. Welding Fundamentals......Page 258
6.3.3. Welding Influence on Behavior of Aluminum Alloys......Page 261
6.3.4. Frequent Corrosion Types of Welded Aluminum Alloys......Page 264
6.3.5. Corrosion Resistance of Wrought and Cast Al Alloys......Page 266
6.4. Metal Matrix Composites for Nuclear Dry Waste Storage......Page 272
6.5.3. Algae (Eukaryotes)......Page 274
6.6.3. Soils......Page 275
6.7.1. Anaerobic Bacteria......Page 276
6.7.3. Co-action of Anaerobic and Aerobic Bacteria......Page 277
6.8.3. Cyanobacteria and Algae (Polluted Freshwater)......Page 279
6.8.5. SRB (Industrial and Seawater)......Page 280
6.9.1. Corrosion Mechanisms......Page 281
6.9.3. Corrosion Inhibition by Microorganisms......Page 283
6.10. MIC Prevention and Control......Page 284
References......Page 285
Overview......Page 288
7.1. Impingement with Liquid-Containing Solid Particles......Page 289
7.2. Corrosion by Cavitation......Page 293
7.3. Water Drop Impingement Corrosion......Page 294
7.5. Fretting Fatigue Corrosion......Page 296
7.7. General Considerations and Morphology......Page 297
7.8.1. Environmental Considerations......Page 298
7.8.2. Cyclic Stresses......Page 299
7.9. Mechanisms of Corrosion Fatigue......Page 302
7.10. Corrosion Fatigue of Aluminum Alloys......Page 303
7.10.1. Corrosion Fatigue of AA7017-T651......Page 304
7.10.3. Corrosion Fatigue of Al–Mg–Si Compared to Al–Mg Alloys......Page 306
7.10.4. Modeling of the Propagation of Fatigue Cracks in Aluminum Alloys......Page 310
7.11. Prevention of Corrosion Fatigue......Page 312
References......Page 313
8.1. Introduction and Definition of SCC......Page 314
8.2.1. Stress......Page 316
8.2.2. Environment......Page 317
8.3.1. Influence of Stress......Page 319
8.3.2. Role of Environment......Page 320
8.4.1. Overlapping of Cracking Phenomena......Page 322
8.4.2. Significance of the Magnitude of Strain Rates......Page 324
8.4.3. Cracking Initiation and Propagation......Page 325
8.5. SCC of Aluminum Alloys......Page 326
8.5.1. SCC Resistance of Aluminum Alloys......Page 327
8.5.2. Influence of Heat Treatments on Corrosion Forms......Page 329
8.6.1. Galvanic Corrosion and SCC of Welded Assemblies......Page 331
8.6.2. SCC Knife-Line Attack......Page 332
8.6.3. Localized Corrosion and SCC of LBW AA6013......Page 333
8.6.5. Corrosion Fatigue of Friction Stir Welding White Zone......Page 335
8.6.6. SCC of Friction Stir Welded 7075 and 6056 Alloys......Page 336
8.6.7. SCC of FSW of 7075-T651 and 7050-T451 Alloys......Page 337
8.7.2. Environmental Considerations......Page 338
8.7.3. Metallurgical Considerations......Page 339
8.7.4. Surface Modification......Page 340
References......Page 341
Part Three Performance and Corrosion Forms of Magnesium and Its Alloys......Page 344
Overview......Page 346
9.1. Physical and General Properties of Magnesium......Page 347
9.2.1. Designation of Cast Magnesium Alloys......Page 348
9.2.2. Alloying Elements......Page 349
9.2.3. Cast Magnesium Alloys Series......Page 350
9.3. Properties of Wrought Magnesium Alloys......Page 353
9.5. Magnesium Composites......Page 358
9.6.2. Mg(2)Si......Page 359
9.7. Applications of Cast Magnesium Alloys......Page 360
9.7.2. Application as Refractory Material......Page 361
9.8. Applications of Wrought Magnesium Alloys......Page 362
9.9. Resistance of Magnesium Alloys to Atmospheric Corrosion......Page 363
9.11. Water Corrosion......Page 365
9.12. Salt Solutions......Page 366
9.15. Dry Organic Compounds......Page 368
9.17. Magnesium High-Temperature Corrosion......Page 369
References......Page 371
A. General Corrosion......Page 373
10.1.1. E(corr) and Corrosion Rates in Natural and Aqueous Media......Page 374
10.1.2. Corrosion Rate Methods of Mg–Al Alloys......Page 376
10.1.3. Critical Evaluation of the Passive Properties of Magnesium Alloys......Page 377
10.2. The Negative Difference Effect (NDE)......Page 378
10.3.1. Electrochemical Noise Studies......Page 383
10.4. Corrosion Prevention......Page 386
B. Galvanic Corrosion......Page 387
10.5. Hydrogen Overpotentials......Page 388
10.6. Galvanic Corrosion of Pure and Alloyed Magnesium......Page 389
10.6.1. Cathodic Corrosion of Aluminum......Page 390
10.7. Composite Coat for Molten Magnesium......Page 391
10.9. Prevention of Galvanic Corrosion......Page 392
10.9.1. Joining Magnesium to Dissimilar Metal Assemblies......Page 393
10.10. Pitting Corrosion......Page 394
10.10.1. The Pitting Potential Determination......Page 395
10.10.2. Polarization Curves and Pitting Potential of AXJ Alloy......Page 397
10.11. Crevice Corrosion......Page 399
10.12.1. Initiation and Kinetics Parameters......Page 400
10.12.2. Mechanism of Propagation......Page 401
References......Page 402
Overview......Page 405
11.1.1. Casting Alloys......Page 406
11.1.3. Alloying Elements and Tolerance Limit......Page 407
11.2.1. Galvanic Corrosion and Secondary Phases......Page 413
11.2.2. Intergranular Corrosion......Page 416
11.2.3. Exfoliation Corrosion......Page 417
11.2.5. Microstructure and Corrosion Creep of Magnesium Die-Cast Alloys......Page 418
11.2.6. The OCP, i(corr), and Corrosion Creep......Page 420
11.2.7. Corrosion Creep and Aging......Page 421
11.3.1. Influence of Heat Treatments......Page 422
11.3.2. Effect of Rapid Solidification......Page 424
11.3.3. Influence of the Microstructure of Some Mg Alloys......Page 426
11.3.4. Influence of Joining and Welding......Page 433
11.3.5. Cold Chamber Processes......Page 436
11.3.6. Hot Chamber Processes and Corrosion Resistance of Thin Plates......Page 443
B. MIC of Magnesium and Magnesium Alloys......Page 446
11.4.1. Behavior of Sacrificial Magnesium......Page 447
11.4.2. Rational Biocorrosion of Mg and Its Alloys in the Human Body......Page 448
11.6.1. Alloying......Page 449
11.6.3. Magnesium Implants and Bone Surgery......Page 451
References......Page 454
12.1.1. Erosion Corrosion......Page 458
12.2. Corrosion Fatigue of Magnesium Alloys......Page 460
12.2.1. Corrosion Fatigue of Cast Magnesium Alloys......Page 461
12.2.3. Crack Propagation of Wrought Extruded Alloys......Page 465
12.2.4. Welding and Corrosion Fatigue of AZ31......Page 471
12.2.5. Mechanisms of Corrosion Fatigue: Initiation and Propagation......Page 473
12.2.6. Prevention of Corrosion Fatigue......Page 474
References......Page 475
13.1. Use of Magnesium Alloys and Stress-Corrosion Cracking Failures......Page 477
13.2.1. Alloy Composition and Magnesium Impurities......Page 478
13.2.2. Microstructure and Crack Morphology......Page 479
13.2.4. Effect of the Environment......Page 481
13.3.3. Pitting and Localized Corrosion......Page 484
13.3.4. Welded Material and SCC......Page 485
13.3.5. Environment-Enhanced Creep and SCC of Mg Alloys......Page 486
13.4.1. Electrochemical Dissolution Models......Page 488
13.4.2. Hydrogen Embrittlement......Page 489
13.5. SCC–HE of Some Magnesium Alloys......Page 492
References......Page 498
Part Four Coating and Testing......Page 502
Overview......Page 504
14.2. Metallic Coatings......Page 506
14.2.2. Surface Preparation for Thermal Spraying......Page 507
14.2.3. Sacrificial Protection by Aluminum Alloys......Page 508
14.2.5. Cathodic Protection of Aluminum Alloys......Page 510
14.3. Conversion Coating......Page 511
14.3.1. Phosphates and/or Chromates......Page 512
14.3.2. Chromate–Phosphate Treatments......Page 515
14.3.3. Chromate Alternatives......Page 516
14.4. Anodization......Page 521
14.5.2. Converted Coating During or After Application......Page 528
14.5.3. Coatings Containing Metals More Active than Aluminum......Page 530
14.5.4. Electrodeposited Coatings......Page 531
14.6.1. Electrochemical Testing of Coatings......Page 532
14.6.3. Corrosion Fatigue of Thermal Spraying of Aluminum as a Coating......Page 533
References......Page 534
15.1. General Approach and Surface Preparation......Page 537
15.2.1. Metallic Coatings......Page 539
15.2.2. Chemical Conversion Surface Treatments......Page 541
15.3.1. Anodizing Description and Approaches......Page 546
15.3.2. Formation of Anodized Coatings......Page 548
15.3.4. Some Industrial and Developing Anodizing Processes......Page 551
15.3.5. Forms of Surface Corrosion: Anodized or with Conversion Treatments......Page 558
15.4.1. Chemical and Physical Vapor Deposition......Page 564
15.4.2. The H-Coat and Magnesium Hydrides......Page 566
15.5.1. OCP and Polarization Studies of the Metal–Oxide Interface......Page 574
15.5.2. Impedance Measurements......Page 575
15.6.1. Organic Coatings......Page 579
15.6.2. Conventional Corrosion Testing of Coated Metal......Page 581
References......Page 586
Part Five Evaluation and Testing......Page 590
Overview......Page 592
16.1.2. Categories of Corrosion Testing......Page 593
16.1.3. Testing Duration......Page 594
16.1.5. Removal of Corrosion Products......Page 595
16.2.1. Visual and Microscopic Techniques of Testing......Page 596
16.2.2. Nondestructive Evaluation Techniques......Page 598
16.2.4. Chemical Analysis......Page 600
16.2.6. Published Data of Performance and Corrosion Resistance......Page 602
16.3. Electrochemical Polarization Studies......Page 604
16.3.2. Potentiodynamic Methods......Page 605
16.3.4. Potentiostatic, Galvanostatic, and Galvanodynamic Methods......Page 608
16.4.1. Introduction......Page 609
16.4.2. EIS Terms and Equivalent Circuits......Page 610
16.4.3. Impedance Plots......Page 614
16.5.1. Historical and Electrochemical Noise Definition......Page 619
16.5.2. EN Generation and Data Acquisition Systems......Page 621
16.5.3. Analysis of ENM Data......Page 625
16.5.4. Potentiodynamic, Potentiostatic, and Galvanostatic EN Studies......Page 637
16.6. Scanning Reference Electrode Technique......Page 638
16.7.1. Microsystems and Atomic Force Microscopy......Page 641
16.7.2. Wire Beam Electrode......Page 642
References......Page 643
Overview......Page 646
17.1. General Corrosion of Aluminum and Its Alloys......Page 649
17.2.1. General Considerations......Page 650
17.2.3. Electrochemical Testing......Page 652
17.3.1. Pitting Corrosion......Page 653
17.3.2. Crevice Corrosion......Page 665
17.4.1. Intergranular Corrosion Testing......Page 666
17.4.2. Exfoliation Testing......Page 667
17.5. MIC and Biodegradation Evaluation......Page 668
17.6.1. Erosion Corrosion Testing......Page 671
17.6.2. Corrosion Fatigue Testing......Page 672
17.7. Environmentally Influenced Corrosion......Page 675
17.7.1. SCC Testing Procedures of Aluminum Alloys......Page 676
17.7.2. Test Specimens......Page 678
17.7.3. Stressors......Page 679
17.7.4. Fracture Morphology and SCC of Aluminum Alloys......Page 682
References......Page 684
Overview......Page 688
18.1.1. Hydroxide Solutions......Page 689
18.1.4. Buffered Solutions......Page 690
18.2.1. Immersion Testing and Corrosion Rate......Page 691
18.2.2. Salt Spray Corrosion Test......Page 694
18.2.3. Some Electrochemical Methods of Investigation......Page 696
18.3. Galvanic or Bimetallic Corrosion of Magnesium and Its Alloys......Page 702
18.4.1. Open Circuit Potential and Pitting Corrosion Studies......Page 703
18.4.2. Electrochemical Noise Measurements......Page 705
18.4.3. Magnesium SRET Studies......Page 709
18.6. MIC and Biodegradation of Magnesium and Its Alloys......Page 713
18.7. Corrosion Fatigue......Page 714
18.8.1. Static Loading of Smooth Specimens and General Considerations......Page 715
18.8.3. Solutions and Operational Conditions......Page 716
18.8.4. Constant Extension Rate and Linearly Increasing Stress Tests......Page 718
18.8.5. SCC CERT Versus LIST Techniques......Page 720
References......Page 721
Part Six Bibliography, International Units, and Abbreviations......Page 724
A1.2. Bibliography of Corrosion Data for Performance of Materials......Page 726
A1.3. ASTM Standards......Page 727
A2.1.1. Constants......Page 728
A2.1.3. Key Equations......Page 729
A2.3. Electrochemical Cells and Their Potentials......Page 731
A2.4. Standard Electrode Potential of Cations (T=25 °C)......Page 732
A2.5. The Periodic Table......Page 733
Appendix 3. Abbreviations and Symbols......Page 734
Index......Page 738