Characterization of the Corrosion and Oxide Film Properties of Alloy 600 and Alloy 800

227 Pages·2017·2.49 MB·English

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Melissa Faichuk, The University of Western Ontario
Supervisor: Dr. David Shoesmith, The University of Western Ontario
A thesis submitted in partial fulfillment of the requirements for the Doctor of Philosophy degree
in Chemistry
© Melissa Faichuk 2013
Follow this and additional works at: https://ir.lib.uwo.ca/etd
Part of the Materials Chemistry Commons, and the Physical Chemistry Commons
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Faichuk, Melissa, "Characterization of the Corrosion and Oxide Film Properties of Alloy 600 and Alloy 800"
(2013). Electronic Thesis and Dissertation Repository. 1777.
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Characterization of the Corrosion and Oxide Film Properties of Alloy 600
and Alloy 800

(Thesis format: Integrated Article)

by

Melissa Gail Faichuk

Graduate Program
In
Chemistry

A thesis submitted in partial fulfillment
of the requirements for the degree of
Doctor of Philosophy

The School of Graduate and Postdoctoral Studies
The University of Western Ontario
London, Ontario, Canada

© Melissa Gail Faichuk 2013

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Abstract
The passive film properties of Alloy 600 and Alloy 800, both of which are used as
steam generator tubing in CANDU reactors, have been studied using techniques such as
polarization scans, electrochemical impedance spectroscopy and X-ray photoelectron and
Auger electron spectroscopies. The composition of the oxides formed in a 0.1 M
Na S O solution have been characterized over a wide range of potentials from the pre-
2 2 3
passive, through the passive to the transpassive regions. These changes have been
correlated to the electrochemical behaviour. A second set of experiments was performed
to determine the effectiveness of surface mechanical attrition treatment (SMAT) as a
method of enhancing the corrosion resistance of the alloys by the creation of a
nanostructured surface layer.
In chapters 3 and 4, the compositional and electrochemical characteristics of the
oxide films formed on Alloy 600 and Alloy 800 are described as a function of applied
film growth potential. A comparison of the two alloys is presented in Chapter 5. The
results show that Alloy 800 exhibits a superior corrosion resistance than Alloy 600. This
was attributed to the more facile formation of a Cr O barrier layer due to the segregation
2 3
of Fe to the outer surface of the oxide and the retention of Ni in the alloy surface. For
Alloy 600, the more noble Ni is not so readily segregated to the outer surface which
results in the formation of a thinner, less protective barrier layer.
The effects of surface deformation induced by SMAT on the properties of the
oxides formed on Alloy 600 and Alloy 800 are discussed in Chapters 6 and 7. This
treatment alters the composition of the films, and generally accelerates their degradation.
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This can be attributed to an increase in ion mobility through the less coherent films
formed on the SMAT damaged surfaces.

Key Words:
Corrosion, Stress Corrosion Cracking (SCC), Passivity, Passive Film, Bilayer Oxide,
Barrier Layer, Alloy 600, Alloy 800, Cr O , Na S O , Surface Mechanical Attrition
2 3 2 2 3
Treatment, SMAT.

iii
Acknowledgements
Firstly, I would like to thank co-supervisors, Dr. Sridhar Ramamurthy and Dr.
David Shoesmith for their guidance and support during my graduate work. Unlike many
of my peers, I was lucky enough to have two fantastic supervisors to help guide me
through my studies.
I would like to thank the members of the Shoesmith and Wren groups, as well as
the staff at Surface Science Western. I feel incredibly lucky to have been able to work
with and learn from such a knowledgeable and hardworking group of people.
Also, Dr. Clara Wren, who took me into her group as one of her own, and Dr.
Jamie Noel, whose patience and humour taught so many invaluable things during my
time at Western.
Without the love and support of my family, I would have never been able to
accomplish what I have, and for that I am grateful.
Finally, I would like to thank Andrew for providing me with the unconditional
love, support and encouragement necessary to get me through the last 5 years. You’re
the best!

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Table of Contents

Abstract…………………………………………………………………………………... ii
Acknowledgements……………………………………………………………………… iv
Table of Contents……………………………………………………………………….... v
List of Symbols and Acronyms………………………………………………….…….... xi
List of Tables…………………………………………………………………………... xiv
List of Figures………………………………………………………………………….. xv

Chapter 1: Introduction……………………………………………………………………1
1.1 Thesis Objectives……………………………………………………………………1
1.2 Materials Background……………………………………………………………….3
1.2.1 Alloy 600 and Alloy 800………………………………………………………...3
1.3 Corrosion…………………………………………………………………………….5
1.3.1 Corrosion Principles……………………………………………………………..5
1.4 Passivation………………………………………………………………………......7
1.5 Bilayer Oxide Film Formation………………………………………………………8
1.6 Oxide Film Growth Mechanisms……………………………………………………9
1.7 Stress Corrosion Cracking…………………………………………………………12
1.8 SCC in CANDU Nuclear Reactors………………………………………………...14
1.8.1 General Overview……………………………………………………………...14
1.8.2 SCC of SG Tubing Materials Alloy 600 and Alloy 800………………….…....15
1.9 Surface Mechanical Attrition Treatment (SMAT) ………………………………...17
1.10 Thesis Summary…………………………………………………………………..19
Chapter 2: Experimental Principles and Details…………………………………………25
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2.1 Electrochemical Techniques……………………………………………………….25
2.1.1 Electrode Cell Arrangement…………………………………………………...25
2.1.2 Anodic Polarization Curve…………………………………….………………26
2.1.3 Potentiostatic Polarization……………………………………………………..26
2.1.4 Electrochemical Impedance Spectroscopy (EIS) …………………...………...26
2.2 Surface Analysis Techniques………………………………………………………31
2.2.1 Scanning Electron Microscopy (SEM) ………………………………………..31
2.2.2 X-ray Photoelectron Spectroscopy (XPS) ……………………………...……..32
2.2.3 Auger Electron Spectroscopy (AES) ………………………………………….34
2.3 Experimental Procedures…………………………………………………………..36
2.3.1 SMAT Sample Preparation…………………………………………………….36
2.3.2 Electrochemical Cell…………………………………………………………...36
2.3.3 Solution Preparation……………………………………………………………37
2.3.4 SEM Sample Mounting……………………………………………..…………38
2.4 Surface Analytical Instrumentation and Procedures……………………………….38
Chapter 3: Behaviour of the Oxide Films Formed on Alloy 600………………………..41
3.1 Introduction………………………………………………………………………...41
3.2 Experimental……………………………………………………………………….42
3.2.1 Sample Preparation…………………………………………………………….42
3.2.2 Electrochemical Measurements………………………………………………..43
3.2.3 Surface Analysis……………………………………………………………….44
3.2.3.1 Auger Electron Spectroscopy (AES)……………………………….……..44
3.2.3.2 X-ray Photoelectron Spectroscopy (XPS)……………………………..….44
3.3 Results……………………………………………………………………………...45
3.3.1 Anodic Polarization……………………………………………………………45
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3.3.2 Electrochemical Impedance Spectroscopy (EIS) ……………………………...46
3.3.3 Surface Analysis – AES…..……………………………………………………51
3.3.4 Surface Analysis – XPS………………………………………………………..56
3.3.5 Sulphur…………………………………………………………………………62
3.4 Discussion………………………………………………………………………….65
3.5 Conclusions………………………………………………………………………...68
Chapter 4: Behaviour of the Oxide Films Formed on Alloy 800 Steam Generator Tubing
in a 0.1 M Na S O Solution……………………………………………………………..73
2 2 3
4.1 Introduction………………………………………………………………………...73
4.2 Experimental……………………………………………………………………….74
4.2.1 Sample Preparation…………………………………………………………….74
4.2.2 Electrochemical Measurements………………………………………………..75
4.2.3 Surface Analysis……………………………………………………………….76
4.2.3.1 Auger Electron Spectroscopy (AES)……………………………………...76
4.2.3.2 X-ray Photoelectron Spectroscopy (XPS)……………………………...…76
4.3 Results……………………………………………………………………………...77
4.3.1 Anodic Polarization……………………………………………………………77
4.3.2 Electrochemical Impedance Spectroscopy (EIS) ……………………………...78
4.3.3 Surface Analysis – AES…..……………………………………………………82
4.3.4 Surface Analysis – XPS…..……………………………………………………88
4.3.5 Sulphur…………………………………………………………………………95
4.4 Discussion and Conclusions……………………………………………………….97
Chapter 5: A Comparison Study of the Oxide Films Formed on Alloy 600 and Alloy
800………………………………………………………………………………………103
5.1 Introduction……………………………………………………………………….103
5.2 Experimental……………………………………………………………………...104
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5.2.1 Sample Preparation…………………………………………………………...104
5.2.2 Electrochemical Measurements………………………………………………105
5.2.3 Surface Analysis……………………………………………………………...105
5.2.3.1 Auger Electron Spectroscopy (AES)………………………………….…105
5.2.3.2 X-ray Photoelectron Spectroscopy (XPS)…………………………….....105
5.3 Results…………………………………………………………………………….105
5.3.1 Anodic Polarization…………………………………………………………..105
5.3.2 Electrochemical Impedance Spectroscopy (EIS) …………………………….107
5.3.3 Surface Analysis – Film Thickness (AES) …………………………………..110
5.3.4 Surface Analysis – Cation Fractions………………………………………….112
5.3.4.1 Fe………………………………………………………………………....112
5.3.4.2 Ni…………………………………………………………………………113
5.3.4.3 Cr…………………………………………………………………………114
5.3.5 Surface Analysis – AES Depth Profiles………………………………………116
5.3.5.1 Fe….……………………………………………………………………...116
5.3.5.2 Ni….…………………………………………………………………...…117
5.3.5.3 Cr…………………………………………………………………………118
5.3.6 Surface Analysis – XPS………………………………………………………120
5.3.7 Sulphur………………………………………………………………………..122
5.4 Discussion………………………………………………………………………...123
5.4.1 Pre-passive and Early Passive Region (-0.4 V to 0 V ) ………………...124
SCE SCE
5.4.2 Anodic Peak Region (0 V to 0.3 V ) …………………………………...125
SCE SCE
5.4.3 Transpassive Region (0.3 V to 0.75 V ) ………………………………..127
SCE SCE
5.5 Conclusions……………………………………………………………………….128
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Chapter 6: Corrosion and Surface Film Properties of Alloy 600 Subjected to Surface
Mechanical Attrition Treatment (SMAT) ……………………………………………...132
6.1 Introduction……………………………………………………………………….132
6.2 Experimental……………………………………………………………………...133
6.2.1 Sample Preparation…………………………………………………………...133
6.2.2 Electrochemical Measurements………………………………………………134
6.2.3 Surface Analysis……………………………………………………………...134
6.2.3.1 Scanning Electron Microscopy (SEM)…………………………………..134
6.2.3.2 Auger Electron Spectroscopy (AES)…………………………………….134
6.2.3.3 X-ray Photoelectron Spectroscopy (XPS)…………………………….…135
6.3 Results…………………………………………………………………………….135
6.3.1 Surface Imaging: Scanning Electron Microscopy (SEM) …………………...135
6.3.2 Anodic Polarization…………………………………………………………..136
6.3.3 Electrochemical Impedance Spectroscopy (EIS) ……………………………138
6.3.4 Surface Analysis – AES………………………………………………………143
6.3.5 Surface Analysis – XPS………………………………………………………153
6.3.6 Sulphur………………………………………………………………………..163
6.4 Discussion…………………..…………………………………………………….166
6.5 Conclusions……………………………………………………………………….168
Chapter 7: Corrosion and Surface Film Properties of Alloy 800 Subjected to Surface
Mechanical Attrition Treatment (SMAT) ……………………………………………...172
7.1 Introduction……………………………………………………………………….172
7.2 Experimental……………………………………………………………………...173
7.2.1 Sample Preparation…………………………………………………………...173
7.2.2 Electrochemical Measurements……………………...…….…………………174
7.2.3 Surface Analysis……………………………………………………………...174
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