Galvanic Corrosion of Carbon Steel-Stainless Steel Welds

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Galvanic Corrosion of Carbon Steel-Stainless Steel Welds, Is A Well-Researched Topic, It Is To Be Used As A Guide Or Framework For Your Research.

Abstract

A water leak in one of the Canada Deuterium Uranium (CANDU) nuclear reactors could lead to galvanic corrosion between the materials of its supporting structures: carbon steel (CS) and stainless steel (SS). This project investigates the effects of physical and chemical solution parameters on the corrosion of galvanically coupled dissimilar CS-SS
welds, with the aim of developing a corrosion dynamics model that can be used to assess the long-term integrity of the CANDU reactor structural materials with confidence. The studied parameters were solution pH, temperature, the presence or absence of γ-radiation and the cathode:anode surface area ratio. Multiple electrochemical techniques were used to measure the corrosion rates of these steels, including the novel Dual-Electrochemical Cell method. These were augmented with post-test surface and solution analyses to study the oxides formed on the corroded surfaces and to determine the amount of dissolved metal
ions in the solution.

This study demonstrated that CS and SS corrosion involve many elementary steps that lead to the dissolution of metal ions as well as the formation and growth of different oxides. Non-linear dynamic behaviours can develop due to the strong coupling between
different elementary processes. Therefore, simple linear-dynamic rate models for the corrosion of CS or a CS-SS couple can result in erroneous evaluations and inaccurate predictions of their long-term performance.

The results also showed that the effects of galvanic coupling to SS, higher temperature, higher cathode: anode surface area ratio or g-irradiation on the corrosion progression of CS have a strong time-dependence. Initially, they increase the corrosion rate of CS. However, these factors also lead to faster oxide formation and growth on CS, suppressing subsequent Fe dissolution over longer time periods. As a result, the increase in the CS corrosion rate due to galvanic coupling diminishes with time.

Table of Contents

Abstract ……………………………………………………………………………………………………………ii
Summary for Lay Audience ……………………………………………………………………………….. iv
Co-Authorship Statement …………………………………………………………………………………… v
Acknowledgements ………………………………………………………………………………………….. vi
Table of Contents ……………………………………………………………………………………………. vii
List of Symbols ………………………………………………………………………………………………xiii
List of Acronyms …………………………………………………………………………………………….. xv
List of Tables ……………………………………………………………………………………………….. xvii
List of Figures ……………………………………………………………………………………………… xviii
Chapter 1. Introduction …………………………………………………………………………………. 1
1.1 Thesis Motivation ……………………………………………………………………… 1
1.2 Research Objective and Approaches …………………………………………….. 4
1.3 Thesis Outline ………………………………………………………………………….. 5
1.4 References ……………………………………………………………………………….. 6
Chapter 2. Technical Background and Literature Review …………………………………… 7
2.1 Carbon Steel and Stainless Steel ………………………………………………….. 7
2.1.1 Microstructure of carbon steel………………………………………………….. 7
2.1.2 Microstructure of stainless steel ……………………………………………….. 9
2.2 Principles of Aqueous Corrosion ……………………………………………….. 11
2.2.1 Thermodynamics of corrosion ……………………………………………….. 11
2.2.2 Kinetics of electrochemical half reactions ………………………………… 12

2.2.3 Mixed potential theory ………………………………………………………….. 13
2.2.4 Principles of galvanic corrosion ……………………………………………… 15
2.3 Principles of Water Radiolysis …………………………………………………… 18
2.3.1 Interaction of ionizing radiation with matter …………………………….. 18
2.3.2 Water radiolysis by γ-radiation ………………………………………………. 20
2.4 Corrosion of Carbon Steel in Reactor Environments ……………………… 23
2.5 Corrosion of Stainless Steel in Reactor Environments ……………………. 27
2.6 Galvanic Corrosion Studies of Carbon Steel ………………………………… 29
2.7 References ……………………………………………………………………………… 32
Chapter 3. Experimental Techniques …………………………………………………………….. 39
3.1 Electrochemical Tests ………………………………………………………………. 39
3.1.1 Electrochemical cell set-up ……………………………………………………. 39
3.1.2 Potentiodynamic polarization analysis …………………………………….. 40
3.1.3 Linear polarization resistance…………………………………………………. 40
3.1.4 Cyclic voltammetry ……………………………………………………………… 41
3.1.5 Coupling potential and coupling current measurements ……………… 41
3.1.6 Dual-electrochemical cell measurement …………………………………… 42
3.2 Surface Analysis and Solution Analysis Techniques ……………………… 44
3.2.1 Comparison of surface analysis techniques ………………………………. 44
3.2.2 Inductively coupled plasma optical emission spectrometry …………. 47

3.3 References ……………………………………………………………………………… 48
Chapter 4. Effect of Solution Properties on the Independent Corrosion of Individual
Carbon Steel and Stainless Steel ………………………………………………………………………… 49
4.1 Introduction ……………………………………………………………………………. 49
4.2 Experimental ………………………………………………………………………….. 50
4.2.1 Electrode and solution preparation ………………………………………….. 50
4.2.2 Electrochemical tests ……………………………………………………………. 51
4.2.3 The dual-electrochemical cell method ……………………………………… 52
4.2.4 Corrosion tests …………………………………………………………………….. 53
4.2.5 Surface characterization and solution analysis…………………………… 53
4.3 Results and Discussion …………………………………………………………….. 54
4.3.1 Effect of pH and temperature on the corrosion of individual alloys . 54
4.3.2 Corrosion currents obtained by different methods ……………………… 70
4.3.3 Comparison of the electrochemical analyses with dissolved metal
analysis …………………………………………………………………………………………. 75
4.4 Conclusions ……………………………………………………………………………. 78
4.5 References ……………………………………………………………………………… 79
Chapter 5. Effect of Solution Properties on the Galvanic Corrosion of a Carbon Steel-
Stainless Steel Couple ……………………………………………………………………………………… 81
5.1 Introduction ……………………………………………………………………………. 81
5.2 Experimental ………………………………………………………………………….. 82

5.2.1 Electrode and electrolyte preparation ………………………………………. 82
5.2.2 Coupling potential and coupling current measurements ……………… 83
5.2.3 Dual-electrochemical cell measurement …………………………………… 84
5.2.4 Surface characterization and solution analysis…………………………… 86
5.3 Results and Discussion …………………………………………………………….. 86
5.3.1 Galvanic corrosion of the CS-SS couple ………………………………….. 86
5.3.2 Corrosion currents obtained by different methods ……………………… 89
5.3.3 Corrosion currents of individual CS, SS and galvanically coupled CSSS
…………………………………………………………………………………………. 94
5.4 Conclusions ………………………………………………………………………….. 106
5.5 References ……………………………………………………………………………. 107
Chapter 6. Effect of Gamma-Radiolysis on the Corrosion Dynamics of Galvanically
Coupled Dissimilar Metals ……………………………………………………………………………… 110
6.1 Introduction ………………………………………………………………………….. 110
6.2 Experimental ………………………………………………………………………… 111
6.2.1 Electrode and electrolyte preparation …………………………………….. 111
6.2.2 Coupling potential and coupling current measurements ……………. 111
6.2.3 Irradiation tests ………………………………………………………………….. 112
6.2.4 Dual-electrochemical cell measurement …………………………………. 112
6.2.5 Corrosion tests …………………………………………………………………… 113

6.2.6 Surface characterization and solution analysis…………………………. 113
6.3 Results and Discussion …………………………………………………………… 114
6.3.1 Effect of g-radiation on the microgalvanic corrosion of CS ……….. 114
6.3.2 Effect of g-radiation on the independent corrosion of individual alloys
……………………………………………………………………………………….. 115
6.3.3 Effect of g-radiation on the galvanic corrosion of the CS-SS couple ….
……………………………………………………………………………………….. 119
6.3.4 Corrosion progression on CS ……………………………………………….. 123
6.4 Conclusions ………………………………………………………………………….. 128
6.5 References ……………………………………………………………………………. 129
Chapter 7. Effect of Surface Area Ratio on the Corrosion Dynamics of Galvanically
Coupled Carbon Steel and Stainless Steel in Different Solution Environments ………… 131
7.1 Introduction ………………………………………………………………………….. 131
7.2 Experimental ………………………………………………………………………… 132
7.2.1 Electrode and electrolyte preparation …………………………………….. 132
7.2.2 Coupling potential and coupling current measurements ……………. 133
7.2.3 Dual-electrochemical cell measurement …………………………………. 133
7.2.4 Cyclic voltammetry measurement …………………………………………. 134
7.2.5 Irradiation tests ………………………………………………………………….. 134
7.3 Results and discussion ……………………………………………………………. 135

7.3.1 Galvanic corrosion of CS-SS: Effect of temperature ………………… 135
7.3.2 Galvanic corrosion of CS-SS: Effect of g-radiation ………………….. 142
7.3.3 Evolution of the reduction current …………………………………………. 143
7.3.4 Cyclic voltammetry of CS in Ar-purged solutions ……………………. 148
7.3.5 Anodic – relationship for CS in aerated solutions …………………. 153
7.4 Conclusions ………………………………………………………………………….. 157
7.5 References ……………………………………………………………………………. 158
Chapter 8. Summary and Future Work…………………………………………………………. 161
8.1 Summary ……………………………………………………………………………… 161
8.2 Future Work …………………………………………………………………………. 164
Appendix A. Curriculum Vitae ………………………………………………………………………… 166

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YourPastQuestions Brand

Additional information

Author

Mi Li

No of Chapters

8

No of Pages

193

Reference

YES

Format

PDF

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