Methodology of Crevice Corrosion Testing for Stainless Steels in Natural and Treated Seawaters

102 Pages·2010·4.29 MB·English

by  Kivisä

European Federation of Corrosion Publications
NUMBER 60
Methodology of crevice
corrosion testing for
stainless steels in natural
and treated seawaters
Edited by
U. Kivisäkk, B. Espelid & D. Féron
Published for the European Federation of Corrosion
by Maney Publishing
on behalf of
The Institute of Materials, Minerals & Mining
Published by Maney Publishing on behalf of the European Federation of Corrosion
and The Institute of Materials, Minerals & Mining
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First published 2010 by Maney Publishing
© 2010, European Federation of Corrosion
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Cover photo from Chapter 4: Assembly of the spring loaded PVDF crevice formers.
Preface
Since the end of the 1980s, many efforts have been made in Europe to understand
crevice corrosion of stainless steels in seawater and to give a practical and an
industrial response to these phenomena. In the 1990s, the work was mainly carried
out as two collaborative research programmes involving a number of European labo-
ratories and test sites in eight countries and in the fi ve ‘European seas’ (Atlantic
Ocean, Baltic, Mediterranean and North Seas, English Channel). One programme
was organised by the Marine Corrosion Working party of the European Federation
of Corrosion and the other by the MArine Science and Technology Directorate
(MAST) of the European Union in Brussels. Results of these two programmes have
been widely presented during European workshops and at Eurocorr; they have been
published in the EFC series (Number 19 and Number 33). At the beginning of the
2000s, the scientifi c knowledge coming from previous programmes was applied
to develop and qualify new reliable and reproducible test methods in order to charac-
ter ise the susceptibility of passive metals to crevice corrosion in marine environments.
This project, called CREV CORR, was initiated and funded by the European
Community under the ‘Com peti tive and Sustainable Growth’ Programme. The main
objective was to develop a crevice corrosion qualifi cation test for stainless steels to be
used in marine environments. Users and manufacturers of stainless steels and other
passive metals have a need for a test metho dol ogy which reliably and reproducibly
characterises the crevice corrosion behaviour of these materials in marine environ-
ments. For years, many methods have been develop ed to characterise the crevice
corrosion behaviour of stain less steels, but the majority of these are of a comparative
nature, aimed only at ranking alloys. There is therefore a need to develop a test
method for passive metals to refl ect reliably and reproducibly the long-term
corrosion behaviour of these materials in natural and treated seawaters.
The objectives of this book are to present the main results obtained which also
include the procedures for crevice corrosion tests discussed and used by more than
20 laboratories. The 10 chapters include a historical perspective of crevice corrosion
(Chapter 1), an overview of the programme developed (Chapter 2), calibration tests
and procedures of the participating laboratories (Chapter 3), and description of
the new crevice formers for plates (Chapter 4) and tubes (Chapter 5). Then ways to
simulate the corrosivity of aerated natural seawater (Chapter 6), anaerobic seawater
(Chapter 7) and mixed conditions (Chapter 8) are proposed and argued. The
biological and oxidation capacity of natural and treated seawaters can also be simu-
lated electrochemically (Chapter 9). The fi nal chapter (Chapter 10) describes results
obtained during large round robin tests performed to compare the developed test
methods with standard tests and natural seawater tests to verify the reliability and
reproducibility of the ‘new’ test methods. All of these methods which have been
developed and implemented in this programme are described in detail in the nine
appendixes of the book which include the calibration procedures (Appendix A), the
xvii
xviii Crevice corrosion testing for stainless steels
procedures for crevice corrosion tests in natural and synthetic biochemical seawaters
for plates (Appendix B), tubes (Appendix C) and umbilical applications (Appendix
F), and the description of the synthetic biochemical seawater (Appendix D). The
electrochemical procedure to simulate aerobic biofi lms is also described in Appendix
E, while special emphasis is given for crevice test procedures used during the round
robin tests in natural seawater (Appendix G) or in biosynthetic seawater (Appendix
H). The method of reporting results is given in Appendix I.
These procedures have been successfully applied during this programme. If they
are widely used, they may improve the success ful application of the materials and
components, thereby minimising replacement costs and costs of claims.
The editors of the volume would like to thank the partners of the CREVCORR-
project: DET NORSKE VERITAS (Norway, coordinator), FORCE Institute
(Denmark), Commissariat à l’Energie Atomique (France), Consiglio Nazionale Del-
le Richerche (Italy), SINTEF (Norway), Shell Global Solutions (The Netherlands),
Avesta Sheffi eld AB (Sweden – later on AvestaPolarit AB and today Outokumpu
Stainless AB), TNO (The Netherlands), Statoil (Norway), AB Sandvik Steel (Sweden
– later on AB Sandvik Materials Technology). In the book, the names of the
affi liations that were used when the work was carried out are used.
The editors hope that the book will be useful to scientists and engineers who are
involved in the selection of stainless steels and passive materials for seawater applica-
tions and will help them to predict reliably and reproducibly the long-term corrosion
behaviour of these materials in seawater and in other chlorinated natural environ-
ments.
Ulf Kivisäkk,
Chairman of the EFC WP on Marine Corrosion
Bård Espelid,
Past-chairman of the EFC WP on Marine Corrosion
Damien Féron,
Chairman of the EFC Science and Technology Advisory Committee (STAC)
Contents
Series introduction x
Volumes in the EFC series xii
Preface xvii
1 Crevice corrosion from a historical perspective 1
1.1 Introduction 1
1.2 The mechanism 1
1.3 The ferric chloride test 2
1.4 Field tests 3
1.5 Electrochemical tests 5
1.6 Conclusions 6
2 Objectives and background 8
2.1 Introduction 8
2.2 Establishment of the state-of-the-art 9
2.3 Formulation of a new synthetic seawater 9
2.4 Electrochemically controlled crevice corrosion test 10
2.5 Inter-comparison testing 10
3 Laboratory calibration 12
3.1 ‘Calibration’ of participating laboratories in the project 12
3.2 Experimental procedure 12
3.3 Test results 12
3.3.1 Weight loss 12
3.3.2 Number of etchings/attacks 13
3.3.3 Maximum depth of attack 16
3.4 Conclusions from the ‘calibration’ test 16
4 Crevice formers for specimens of plate material 17
4.1 Optimisation of test parameters of importance for crevice
corrosion testing 17
5 Crevice corrosion testing of tubes 21
5.1 Introduction 21
5.2 Experimental 22
5.2.1 Materials 22
5.2.2 Design of crevice former 22
5.2.3 Finite Element Method Modelling 23
5.2.4 Crevice corrosion testing 23
5.3 Results 24
5.3.1 Finite Element Method modelling 24
5.3.2 Crevice corrosion testing 24
v
vi Contents
5.4 Discussion 26
5.4.1 Specimen area 27
5.4.2 Crevice former 27
5.4.3 Clamping force 27
5.4.4 Proposed crevice former procedure for tube
specimens 28
5.5 Crevice corrosion testing of stainless steel tubes applied as
umbilicals 28
5.6 Conclusions from crevice corrosion testing of tubes 28
6 Formulation of new synthetic seawater for aerobic environments 30
6.1 Introduction 30
6.2 Experimental 31
6.3 Electrochemical tests 32
6.4 Crevice corrosion experiments 33
6.4.1 After test examination 34
6.4.2 Chemical method versus the biochemical method 34
6.4.3 Infl uence of the tank material 38
6.4.4 Infl uence of the cathodic area 39
6.4.5 Infl uence of stainless steel grades 39
6.4.6 Infl uence of chemicals and biochemicals 40
6.4.7 Infl uence of temperature 41
6.4.8 Infl uence of the crevice holder system 41
6.5 Conclusion 42
7 Simulation of anaerobic environments 44
7.1 Introduction 44
7.2 Experimental 44
7.3 Results and discussion 46
7.3.1 Infl uence of the polarisation scanning rate 46
7.3.2 Breakdown potentials in sterile aerated seawater 48
7.3.3 Breakdown potentials in anaerobic seawater with SRB 50
7.3.4 Breakdown potentials NaS solution 51
2
7.4 Conclusion 52
8 Synergy of aerobic and anaerobic conditions 53
8.1 Introduction 53
8.2 Synergy of aerobic and anaerobic biofi lms on EN 1.4404 54
8.3 Synergy of aerobic and anaerobic biofi lms on EN 1.4462
and EN 1.4547 57
8.4 Laboratory simulation of the synergy 58
8.5 Conclusion 58
9 Electrochemical simulation of aerobic environments with or
without chlorine 60
9.1 Electrochemical simulation of biofi lm effects and treatment
of seawaters 60
9.2 Conclusions from activities related to electrochemical
simulation of natural and treated seawaters 66
Contents vii
10 Profi ciency of crevice corrosion methods: inter-comparison tests 67
10.1 Introduction 67
10.2 Experimental 68
10.2.1 Materials 68
10.2.2 Test procedure – general 68
10.2.3 Synthetic biochemical seawater tests 69
10.2.4 Natural seawater tests 70
10.3 Results 71
10.3.1 Natural seawater tests 71
10.3.2 Synthetic biochemical seawater tests 78
10.4 Discussion 78
10.4.1 Natural seawater 78
10.4.2 Spring loaded crevice formers 81
10.4.3 Corrosivity of the synthetic biochemical seawater
versus natural seawater 83
10.4.4 Synthetic biochemical seawater and Critical Crevice
Temperature 84
10.5 Conclusion 87
Appendix A Calibration procedures for crevice corrosion tests in 6% FeCl 88
3
A.1 Scope 88
A.2 References 88
A.3 Test material 88
A.4 Test specimen 88
A.5 Specimen treatment 88
A.6 Crevice formers 88
A.7 Assembling of crevice formers 89
A.8 Apparatus 90
A.9 Test solution 90
A.10 Test temperatures 90
A.11 Procedure 92
A.12 Evaluation 92
A.13 Report 92
Appendix B Crevice corrosion tests in natural seawater and synthetic
biochemical seawater: Test procedures for CREVCORR
round robin tests 94
B.1 Scope 94
B.2 References 94
B.3 Test material 94
B.4 Test specimen 94
B.5 Specimen treatment 95
B.6 Crevice assembly 95
B.7 Assembly of crevice formers 95
B.8 Electrical connections and suspension method 97
B.9 Apparatus 97
B.10 Test solution 97
B.11 Test temperatures 97
B.12 Test procedure 98
viii Contents
B.13 Post-cleaning of specimens 98
B.14 Evaluation 98
B.15 Report 98
Appendix C Stainless steel tubes: Procedures for making a crevice with
similar crevice geometry as for plate specimens 100
C.1 Scope 100
C.2 References 100
C.3 Test material 100
C.4 Test specimen 100
C.5 Specimen treatment 101
C.6 Crevice assembly 101
C.7 Assembly of crevice formers 102
C.8 Electrical connections and suspension method 103
C.9 Testing 103
C.10 Post-cleaning of specimens 104
C.11 Evaluation 104
Appendix D ISO proposal for synthetic biochemical seawater 105
D.1 Scope 107
D.2 Reference documents 107
D.3 Signifi cance and use 108
D.4 Reagents 108
D.5 Preparation of chemical substitute seawater 108
D.6 Preparation of biochemical substitute seawater 109
Appendix E Electrochemical procedures to simulate aerobic biofi lms for
the evaluation of crevice corrosion resistance to various types
of seawater 110
E.1 Scope 110
E.2 Test material 110
E.3 Test specimen 110
E.4 Specimen preparation 110
E.5 Crevice assembly 110
E.6 Electrical connections and suspension method 111
E.7 Apparatus 111
E.8 Test solution 112
E.9 Test temperatures 112
E.10 Test procedure 112
E.11 Evaluation 112
E.12 Report 112
E.13 Method A – Electrochemical crevice corrosion test simulating
natural seawater 113
E.14 Method B – Electrochemical crevice corrosion test simulating
chlorinated natural seawater 114
E.15 Method C – Electrochemical crevice corrosion test simulating
high-temperature chloride solution 115
Contents ix
Appendix F Crevice corrosion tests in natural seawater for umbilical
applications: Test procedures simulating the crevice corrosion
situation inside an umbilical 117
F.1 Scope 117
F.2 References 117
F.3 Test parameters 117
F.4 Test specimens 117
F.5 Specimen treatment 118
F.6 Crevice assembly 118
F.7 Assembling of crevice formers 119
F.8 Electrical connections and suspension method 120
F.9 Apparatus 121
F.10 Test solution 122
F.11 Test temperatures 122
F.12 Test procedure 122
F.13 Post-cleaning of specimens 122
F.14 Evaluation 122
Appendix G General procedure for crevice corrosion tests in natural
seawater: Used for the CREVCORR round robin test 124
G.1 Apparatus 124
G.2 Test solution 124
G.3 Test temperatures 124
G.4 Test procedure 124
G.5 Report 125
G.6 Time development for the natural seawater test 126
Appendix H General procedures for crevice corrosion tests in synthetic
biochemical seawater: Used for the CREVCORR round
robin test 128
H.1 Apparatus 128
H.2 Test solution 128
H.3 Test temperatures 130
H.4 Test procedure 130
H.5 Report 130
H.6 Development of the test for synthetic biochemical seawater 131
H.7 Example of the product document delivered with crude
‘GLUCOSE OXIDASE’ 132
H.8 Example of report 133
Appendix I Report format of crevice corrosion test 134
1
Crevice corrosion from a historical perspective
Bengt Wallén
Avesta, Sweden
1.1 Introduction
Crevice corrosion is a very important type of corrosion of stainless steels, and in
chloride solutions such as seawater, it is often the factor determining the life of a
construction. However, crevice corrosion has not always been recognised as a danger.
This chapter describes how our understanding of the crevice corrosion mechanism
has developed over the years and how different types of tests have come and
sometimes gone. All seen from an industrial corrosion laboratory’s viewpoint.
1.2 The mechanism
Accelerated corrosion in creviced areas on iron was reported quite early on [1].
Stainless steels were invented in 1912 but it took some time before crevice corrosion
was reported for this type of alloy. In a pioneering book from 1926, Monypenny
noted that when testing stainless steels in chloride solutions, ‘corrosion almost invari-
ably starts at the point of support and is often entirely confi ned to that point’ [2]. This
is still a well known problem to anyone performing crevice corrosion tests.
In the early days, there was great optimism regarding the corrosion resistance
of stainless steels. For instance, in a textbook from 1933, Type 304 is considered as
suffi ciently resistant to chloride solutions such as seawater although warnings were
given for the risk of pitting corrosion associated with surface defects. Only in strong
chloride solutions such as brines and hypochlorite solutions were molybdenum
alloyed steels considered necessary [3]. Figure 1.1 shows another example of this
optimism. The protocol shows the result of an Avesta investigation from 1930.
Different steels, among them the very fi rst duplex steels (453E and 453S), were tested
in seawater at 50°C. The corrosion rate was very low and there were no comments as
to localised corrosion!
In Avesta’s fi rst Corrosion Table published in 1934, crevice corrosion was not
mentioned at all. However, in his textbook from 1937, Evans refers to papers pub-
lished in the early 1930s describing ‘remarkable examples of pitting of stainless steels
by cranny action’ [4]. Evans introduces the term crevice or cranny corrosion and sug-
gests differential aeration as the mechanism. A few years later, Smith [5] and Uhlig
[6] described ‘contact corrosion’ which appears in connection with dirt accumulation
on the steel surface or attached barnacles in seawater installations. This is considered
as a special case of pitting corrosion caused by differential aeration. Over the years,
different mechanisms have been proposed but a unifi ed mechanism was not presented
until 1967 in the textbook of Fontana and Greene [7].
1