Corrosion Science and Engineering

737 Pages·2018·21.904 MB·English

by  Pietro Pedeferri

Engineering Materials
Pietro Pedeferri
Corrosion
Science and
Engineering
Edited by Luciano Lazzari and
MariaPia Pedeferri
Engineering Materials
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Pietro Pedeferri
Corrosion Science
and Engineering
Edited by Luciano Lazzari and MariaPia Pedeferri
In Cooperation with Marco Ormellese, Andrea Brenna,
Silvia Beretta, Fabio Bolzoni, Maria Vittoria Diamanti
123
Pietro Pedeferri (Deceased)
Politecnico di Milano
Milan,Italy
ISSN 1612-1317 ISSN 1868-1212 (electronic)
Engineering Materials
ISBN978-3-319-97624-2 ISBN978-3-319-97625-9 (eBook)
https://doi.org/10.1007/978-3-319-97625-9
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Preface
ThisPedeferri’sCorrosionScienceandEngineeringtextbookistheEnglishedition
of Pietro Pedeferri’s Corrosione e Protezione dei Materiali, Polipress, Milano
(2007), with many integrations made by his collaborators of the PoliLaPP, the
Laboratory of Corrosion of Materials that Pedeferri founded. The main goal while
translatingandintegratingtheoriginalItalianbook,sofarveryappreciatedinItaly
with about 2000 copies printed, is to give a modern and updated handbook on
corrosionandcorrosion preventionfor atwofolduse: asateaching textbookanda
modern, technical support for industrial applications. This textbook stands as an
ideal learning resource for students of corrosion courses in chemical, mechanical,
energyandmaterialsengineeringatgraduateandadvancedundergraduatelevels,as
well as a valuable reference for engineers.
ThisEnglishedition, integratedandupdated,contains 30chapters, dealingwith
corrosion theory (9 chapters), forms of corrosion (7), corrosion control and pre-
vention methods (3), applications in different environments as waters, air, soil,
concrete (4), and industrial applications as petrochemical plants, refinery and high
temperature (2) as well as corrosion of implants in the human body. Four chapters
are dedicated to design, corrosion monitoring, laboratory tests and the statistical
processing of corrosion data. Chapters dedicated to the on-field applications pro-
poseanoverviewofthemostusedmetalsandrelevantcasehistories.Emphasishas
been devoted to cathodic protection and corrosion of reinforced concrete to give
merit to the pioneering works carried out by Pietro Pedeferri. Each chapter is
enriched by pictures of corrosion case studies analysed by PoliLaPP; most of the
samples are actually available at the “Corrosion Museum”, where Pietro Pedeferri
and his school have collected the most significant corrosion case studies.
The book offers the reader and the user many case histories and an important
numberofquestionsandexercisestohelpchecktheacquiredknowledge.Questions
and exercises included in each chapter represent the experience gathered by
Pedeferri and his school over the last 50 years as a fruit of teaching, research,
consultancy on material selection, failure analysis and corrosion engineering.
Answers and solutions of exercises for readers will be available on PoliLaPP
website (http://polilapp.chem.polimi.it).
v
vi Preface
Finally, a warm thank to all collaborators Andrea Brenna Silvia Beretta, Fabio
Bolzoni, Maria Vittoria Diamanti for their hard, precious and tenacious work in
contributingtothetranslation,integrationandrevisionofthechaptersandtheeffort
spent on collecting more than 300 exercises. Special mention to Marco Ormellese
for the unparalleled contribution. Thanks to Roberto Chiesa for reviewing the
chapter related to corrosion in the human body, Giorgio Re for the suggestions on
chapters dedicated to environmental-assisted cracking, Eleonora Faccioli for the
drawing offigures and tables and Davide Prando for the collection of the original
pictures.
Milan, Italy Luciano Lazzari
June 2018 MariaPia Pedeferri
Contents
1 General Principles of Corrosion . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1 Corrosion as Metallurgy in Reverse . . . . . . . . . . . . . . . . . . . . 2
1.2 The Economic Impact of Corrosion . . . . . . . . . . . . . . . . . . . . 3
1.3 Corrosion Forms. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.3.1 Uniform or Generalized Corrosion. . . . . . . . . . . . . . 5
1.3.2 Localized Corrosion . . . . . . . . . . . . . . . . . . . . . . . . 7
1.3.3 Stress Corrosion Cracking. . . . . . . . . . . . . . . . . . . . 7
1.4 Corrosion Rates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
1.4.1 Uniform Corrosion . . . . . . . . . . . . . . . . . . . . . . . . . 8
1.4.2 Localized Corrosion . . . . . . . . . . . . . . . . . . . . . . . . 9
1.5 Corrosion Mechanisms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
1.6 Questions and Exercises . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
2 Electrochemical Mechanism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
2.1 Electrochemical Processes . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
2.2 Historical Notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
2.2.1 Evans’s Experiences . . . . . . . . . . . . . . . . . . . . . . . . 20
2.3 Local Cell Theory. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
2.3.1 Mixed Potential Theory. . . . . . . . . . . . . . . . . . . . . . 24
2.4 Corrosion Reactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
2.4.1 Anodic Process. . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
2.4.2 Cathodic Processes . . . . . . . . . . . . . . . . . . . . . . . . . 26
2.4.3 Other Cathodic Processes . . . . . . . . . . . . . . . . . . . . 27
2.4.4 Complementary Processes . . . . . . . . . . . . . . . . . . . . 27
2.5 Stoichiometry (Faraday Law). . . . . . . . . . . . . . . . . . . . . . . . . 28
2.5.1 Corrosion Current Density. . . . . . . . . . . . . . . . . . . . 28
2.6 Change of the Environment. . . . . . . . . . . . . . . . . . . . . . . . . . 28
2.7 Questions and Exercises . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
vii
viii Contents
3 Thermodynamics of Aqueous Corrosion. . . . . . . . . . . . . . . . . . . . . 37
3.1 Driving Voltage and Free Energy. . . . . . . . . . . . . . . . . . . . . . 38
3.2 Corrosion and Immunity Condition . . . . . . . . . . . . . . . . . . . . 39
3.3 Standard Potential. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
3.4 Potential of an Electrochemical Reaction . . . . . . . . . . . . . . . . 43
3.5 Potential of Metal Dissolution Reaction . . . . . . . . . . . . . . . . . 44
3.5.1 Corrosion and Immunity Conditions . . . . . . . . . . . . 45
3.6 Potential of Cathodic Processes . . . . . . . . . . . . . . . . . . . . . . . 45
3.6.1 Potential of Hydrogen Evolution Reaction . . . . . . . . 46
3.6.2 Potential of Oxygen Reduction Reaction . . . . . . . . . 47
3.6.3 Applications of Thermodynamic Criteria . . . . . . . . . 48
3.7 Insoluble Products and Complexing Species . . . . . . . . . . . . . . 50
3.8 Reference Electrodes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
3.9 Electrochemical Cells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
3.9.1 Concentration Cells. . . . . . . . . . . . . . . . . . . . . . . . . 53
3.10 Questions and Exercises . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
4 Pourbaix Diagrams. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
4.1 Oxygen Reduction and Hydrogen Evolution. . . . . . . . . . . . . . 58
4.2 Metal Immunity, Corrosion and Passivation . . . . . . . . . . . . . . 58
4.2.1 Equilibrium Between Immunity and Corrosion . . . . . 59
4.2.2 Equilibrium Between Immunity and Passivation . . . . 61
4.2.3 Equilibrium Between Corrosion and Passivation. . . . 62
4.3 Amphoteric Metals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
4.3.1 Electrochemical Dissolution in Alkaline Solution . . . 63
4.3.2 Chemical Dissolution in Alkaline Solution. . . . . . . . 64
4.4 Pourbaix Diagrams of Some Metals at 25 °C . . . . . . . . . . . . . 64
4.5 Final Remarks. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
4.6 Questions and Exercises . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
5 Kinetics of Aqueous Corrosion . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
5.1 Driving Force and Corrosion Rate . . . . . . . . . . . . . . . . . . . . . 74
5.2 Dissipations in Corrosion Systems . . . . . . . . . . . . . . . . . . . . . 75
5.3 Activation Overvoltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
5.3.1 Exchange Current Density and Tafel Law . . . . . . . . 76
5.3.2 Potential-Current Density Diagrams (or
Characteristic Curves). . . . . . . . . . . . . . . . . . . . . . . 79
5.3.3 Oxidation or Reduction of a Metal. . . . . . . . . . . . . . 81
5.3.4 Hydrogen Evolution (Activation Overvoltage) . . . . . 82
5.3.5 Oxygen Reduction (Activation Overvoltage). . . . . . . 85
5.4 Concentration Overvoltage. . . . . . . . . . . . . . . . . . . . . . . . . . . 85
5.4.1 Oxygen Reduction: Limiting Current . . . . . . . . . . . . 87
Contents ix
5.4.2 Total Oxygen Overvoltage . . . . . . . . . . . . . . . . . . . 89
5.5 Other Cathodic Processes . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
5.6 Passivation and Passivity. . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
5.6.1 Film Formation Mechanisms . . . . . . . . . . . . . . . . . . 92
5.6.2 Oxide Properties. . . . . . . . . . . . . . . . . . . . . . . . . . . 95
5.6.3 Active-Passive Metals. . . . . . . . . . . . . . . . . . . . . . . 95
5.6.4 Passivity-Related Parameters . . . . . . . . . . . . . . . . . . 97
5.7 Questions and Exercises . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102
6 Evans Diagrams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103
6.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104
6.2 Evans Diagrams of Active Metals . . . . . . . . . . . . . . . . . . . . . 104
6.3 Corrosion Conditions in the Presence of an Ohmic Drop. . . . . 108
6.4 Multiple Cathodic Processes . . . . . . . . . . . . . . . . . . . . . . . . . 110
6.5 Imposed Polarization. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111
6.6 Experimental Polarization Curves. . . . . . . . . . . . . . . . . . . . . . 112
6.7 Questions and Exercises . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115
Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118
7 Corrosion Factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119
7.1 Metal Affecting Factors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120
7.1.1 Modification of Metal Surface Composition . . . . . . . 120
7.1.2 Nobility by Alloying. . . . . . . . . . . . . . . . . . . . . . . . 121
7.1.3 Overvoltage of Cathodic Processes . . . . . . . . . . . . . 122
7.1.4 Cathodic Alloying. . . . . . . . . . . . . . . . . . . . . . . . . . 122
7.1.5 Reduction of Anodic Areas . . . . . . . . . . . . . . . . . . . 124
7.1.6 Passivation Induced by Alloying . . . . . . . . . . . . . . . 124
7.2 Environment Affecting Factors. . . . . . . . . . . . . . . . . . . . . . . . 124
7.2.1 Conductivity. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125
7.2.2 pH. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126
7.2.3 Differential Aeration . . . . . . . . . . . . . . . . . . . . . . . . 126
7.2.4 Salt Formation/Precipitation. . . . . . . . . . . . . . . . . . . 128
7.2.5 Cation Displacement. . . . . . . . . . . . . . . . . . . . . . . . 129
7.2.6 Microorganisms . . . . . . . . . . . . . . . . . . . . . . . . . . . 130
7.3 Metal/Environment Affecting Factors . . . . . . . . . . . . . . . . . . . 133
7.3.1 Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133
7.3.2 Condensation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134
7.3.3 Corrosion Products and Deposits . . . . . . . . . . . . . . . 135
7.3.4 Flow Regime . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135
7.3.5 Active–Passive Related Parameters . . . . . . . . . . . . . 135
7.4 Questions and Exercises . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140
Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143