Stress Corrosion Cracking of Pipelines Book

Foreword xiii

Preface xv

List of Abbreviations and Symbols xix

1 Introduction 1

1.1 Pipelines as “Energy Highways” / 2

1.2 Pipeline Safety and Integrity Management / 3

1.3 Pipeline Stress Corrosion Cracking / 3

References / 5

2 Fundamentals of Stress Corrosion Cracking 7

2.1 Definition of Stress Corrosion Cracking / 7

2.2 Specific Metal–Environment Combinations / 9

2.3 Metallurgical Aspects of SCC / 11

2.3.1 Effect of Strength of Materials on SCC / 11

2.3.2 Effect of Alloying Composition on SCC / 11

2.3.3 Effect of Heat Treatment on SCC / 11

2.3.4 Grain Boundary Precipitation / 12

2.3.5 Grain Boundary Segregation / 12

2.4 Electrochemistry of SCC / 13

2.4.1 SCC Thermodynamics / 13

2.4.2 SCC Kinetics / 14

2.5 SCC Mechanisms / 15

2.5.1 SCC Initiation Mechanisms / 15

2.5.2 Dissolution-Based SCC Propagation / 16

2.5.3 Mechanical Fracture–Based SCC Propagation / 18

2.6 Effects of Hydrogen on SCC and Hydrogen Damage / 20

2.6.1 Sources of Hydrogen / 20

2.6.2 Characteristics of Hydrogen in Metals / 21

2.6.3 The Hydrogen Effect / 21

2.6.4 Mechanisms of Hydrogen Damage / 25

2.7 Role of Microorganisms in SCC / 27

2.7.1 Microbially Influenced Corrosion / 27

2.7.2 Microorganisms Involved in MIC / 29

2.7.3 Role of MIC in SCC Processes / 31

2.8 Corrosion Fatigue / 32

2.8.1 Features of Fatigue Failure / 33

2.8.2 Features of Corrosion Fatigue / 34

2.8.3 Factors Affecting CF and CF Management / 35

2.9 Comparison of SCC, HIC, and CF / 35

References / 37

3 Understanding Pipeline Stress Corrosion Cracking 43

3.1 Introduction / 43

3.2 Practical Case History of SCC in Pipelines / 44

3.2.1 Case 1: SCC of Enbridge Glenavon Pipelines (SCC in an Oil Pipeline) / 45

3.2.2 Case 2: SCC of Williams Lake Pipelines (SCC in a Gas Pipeline) / 46

3.3 General Features of Pipeline SCC / 46

3.3.1 High-pH SCC of Pipelines / 47

3.3.2 Nearly Neutral–pH SCC of Pipelines / 48

3.3.3 Cracking Characteristics / 48

3.4 Conditions for Pipeline SCC / 50

3.4.1 Corrosive Environments / 50

3.4.2 Susceptible Line Pipe Steels / 53

3.4.3 Stress / 58

3.5 Role of Pressure Fluctuation in Pipelines: SCC or Corrosion Fatigue? / 62

References / 68

4 Nearly Neutral–pH Stress Corrosion Cracking of Pipelines 73

4.1 Introduction / 73

4.2 Primary Characteristics / 73

4.3 Contributing Factors / 75

4.3.1 Coatings / 75

4.3.2 Cathodic Protection / 79

4.3.3 Soil Characteristics / 81

4.3.4 Microorganisms / 83

4.3.5 Temperature / 85

4.3.6 Stress / 85

4.3.7 Steel Metallurgy / 88

4.4 Initiation of Stress Corrosion Cracks from Corrosion Pits / 89

4.5 Stress Corrosion Crack Propagation Mechanism / 96

4.5.1 Role of Hydrogen in Enhanced Corrosion of Steels / 96

4.5.2 Potential-Dependent Nearly Neutral–pH SCC of Pipelines / 99

4.5.3 Pipeline Steels in Nearly Neutral–pH Solutions: Always Active Dissolution? / 101

4.6 Models for Prediction of Nearly Neutral–pH SCC Propagation / 104

References / 111

5 High-pH Stress Corrosion Cracking of Pipelines 117

5.1 Introduction / 117

5.2 Primary Characteristics / 117

5.3 Contributing Factors / 118

5.3.1 Coatings / 118

5.3.2 Cathodic Protection / 119

5.3.3 Soil Characteristics / 123

5.3.4 Microorganisms / 125

5.3.5 Temperature / 125

5.3.6 Stress / 125

5.3.7 Metallurgies / 128

5.4 Mechanisms for Stress Corrosion Crack Initiation / 128

5.4.1 Electrochemical Corrosion Mechanism of Pipeline Steels in a Thin Layer of Carbonate–Bicarbonate Electrolyte Trapped Under a Disbonded Coating / 128

5.4.2 Conceptual Model for Initiation of Stress Corrosion Cracks in a High-pH Carbonate–Bicarbonate Electrolyte Under a Disbonded Coating / 133

5.5 Mechanisms for Stress Corrosion Crack Propagation / 137

5.5.1 Enhanced Anodic Dissolution at a Crack Tip / 137

5.5.2 Enhanced Pitting Corrosion at a Crack Tip / 143

5.5.3 Relevance to Grain Boundary Structure / 144

5.6 Models for the Prediction of a High-pH Stress Corrosion Crack Growth Rate / 144

References / 145

6 Stress Corrosion Cracking of Pipelines in Acidic Soil Environments 149

6.1 Introduction / 149

6.2 Primary Characteristics / 150

6.3 Electrochemical Corrosion Mechanism of Pipeline Steels in Acidic Soil Solutions / 151

6.4 Mechanisms for Initiation and Propagation of Stress Corrosion Cracks / 151

6.5 Effect of Strain Rate on the SCC of Pipelines in Acidic Soils / 154

References / 157

7 Stress Corrosion Cracking at Pipeline Welds 159

7.1 Introduction / 159

7.2 Fundamentals of Welding Metallurgy / 160

7.2.1 Welding Processes / 160

7.2.2 Welding Solidification and Microstructure / 160

7.2.3 Parameters Affecting the Welding Process / 162

7.2.4 Defects at the Weld / 162

7.3 Pipeline Welding: Metallurgical Aspects / 163

7.3.1 X70 Steel Weld / 163

7.3.2 X80 Steel Weld / 163

7.3.3 X100 Steel Weld / 164

7.4 Pipeline Welding: Mechanical Aspects / 164

7.4.1 Residual Stress / 164

7.4.2 Hardness of the Weld / 166

7.5 Pipeline Welding: Environmental Aspects / 170

7.5.1 Introduction of Hydrogen into Welds / 170

7.5.2 Corrosion at Welds / 172

7.5.3 Electrochemistry of Localized Corrosion at Pipeline Welds / 173

7.6 SCC at Pipeline Welds / 178

7.6.1 Effects of Material Properties and Microstructure / 178

7.6.2 Effects of the Welding Process / 179

7.6.3 Hydrogen Sulfide SCC of Pipeline Welds / 179

References / 180

8 Stress Corrosion Cracking of High-Strength Pipeline Steels 185

8.1 Introduction / 185

8.2 Development of High-Strength Steel Pipeline Technology / 186

8.2.1 Evolution of Pipeline Steels / 186

8.2.2 High-Strength Steels in a Global Pipeline Application / 187

8.3 Metallurgy of High-Strength Pipeline Steels / 189

8.3.1 Thermomechanical Controlled Processing / 189

8.3.2 Alloying Treatment / 189

8.3.3 Microstructure of High-Strength Steels / 190

8.3.4 Metallurgical Defects / 192

8.4 Susceptibility of High-Strength Steels to Hydrogen Damage / 193

8.4.1 Hydrogen Blistering and HIC of High-Strength Pipeline Steels / 193

8.4.2 Hydrogen Permeation Behavior of High-Strength Pipeline Steels / 196

8.5 Metallurgical Microelectrochemistry of High-Strength Pipeline Steels / 199

8.5.1 Microelectrochemical Activity at Metallurgical Defects / 199

8.5.2 Preferential Dissolution and Pitting Corrosion Around Inclusions / 203

8.6 Strain Aging of High-Strength Steels and Its Implication on Pipeline SCC / 207

8.6.1 Basics of Strain Aging / 208

8.6.2 Strain Aging of High-Strength Pipeline Steels / 212

8.6.3 Effect of Strain Aging on SCC of High-Strength Pipeline Steels / 214

8.7 Strain-Based Design of High-Strength Steel Pipelines / 216

8.7.1 Strain Due to Pipe–Ground Movement / 217

8.7.2 Parametric Effects on Cracking of Pipelines Under SBD / 218

8.8 Mechanoelectrochemical Effect of Corrosion of Pipelines Under Strain / 219

References / 225

9 Management of Pipeline Stress Corrosion Cracking 231

9.1 SCC in Pipeline Integrity Management / 231

9.1.1 Elements of Pipeline Integrity Management / 231

9.1.2 Initial Assessment and Investigation of SCC Susceptibility / 234

9.1.3 Classification of SCC Severity and Postassessment / 235

9.1.4 SCC Site Selection / 236

9.1.5 SCC Risk Assessment / 238

9.2 Prevention of Pipeline SCC / 240

9.2.1 Selection and Control of Materials / 241

9.2.2 Control of Stress / 242

9.2.3 Control of Environments / 243

9.3 Monitoring and Detection of Pipeline SCC / 244

9.3.1 In-Line Inspections / 244

9.3.2 Intelligent Pigs / 247

9.3.3 Hydrostatic Inspection / 248

9.3.4 Pipeline Patrolling / 249

9.4 Mitigation of Pipeline SCC / 249

References / 251

Index 255