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- Herausgeber: John Wiley & Sons
- Kategorie: Fachliteratur
- Sprache: Englisch
Provides comprehensive coverage of organic corrosion inhibitors used in modern industrial platforms, including current developments in the design of promising classes of organic corrosion inhibitors Corrosion is the cause of significant economic and safety-related problems that span across industries and applications, including production and processing operations, transportation and public utilities infrastructure, and oil and gas exploration. The use of organic corrosion inhibitors is a simple and cost-effective method for protecting processes, machinery, and materials while remaining environmentally acceptable. Organic Corrosion Inhibitors: Synthesis, Characterization, Mechanism, and Applications provides up-to-date coverage of all aspects of organic corrosion inhibitors, including their fundamental characteristics, synthesis, characterization, inhibition mechanism, and industrial applications. Divided into five sections, the text first covers the basics of corrosion and prevention, experimental and computational testing, and the differences between organic and inorganic corrosion inhibitors. The next section describes various heterocyclic and non-heterocyclic corrosion inhibitors, followed by discussion of the corrosion inhibition characteristics of carbohydrates, amino acids, and other organic green corrosion inhibitors. The final two sections examine the corrosion inhibition properties of carbon nanotubes and graphene oxide, and review the application of natural and synthetic polymers as corrosion inhibitors. Featuring contributions by leading researchers and scientists from academia and industry, this authoritative volume: * Discusses the latest developments and issues in the area of corrosion inhibition, including manufacturing challenges and new industrial applications * Explores the development and implementation of environmentally-friendly alternatives to traditional toxic corrosion inhibitors * Covers both established and emerging classes of corrosion inhibitors as well as future research directions * Describes the anticorrosive mechanisms and effects of acyclic, cyclic, natural, and synthetic corrosion inhibitors Offering an interdisciplinary approach to the subject, Organic Corrosion Inhibitors: Synthesis, Characterization, Mechanism, and Applications is essential reading for chemists, chemical engineers, researchers, industry professionals, and advanced students working in fields such as corrosion inhibitors, corrosion engineering, materials science, and applied chemistry.
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Table of Contents
Cover
Title Page
Copyright Page
Preface
About the Editors
List of Contributors
Part 1: Basics of Corrosion and Prevention
1 An Overview of Corrosion
1 Introduction
References
2 Methods of Corrosion Monitoring
2.1 Introduction
2.2 Methods and Discussion
2.3 Conclusion
References
3 Computational Methods of Corrosion Monitoring
3.1 Introduction
3.2 Quantum Chemical (QC) Calculations‐Based DFT Method
3.3 Atomistic Simulations
Acknowledgments
Suggested Reading
References
4 Organic and Inorganic Corrosion Inhibitors
4.1 Introduction
4.2 Corrosion Inhibitors
References
Part 2: Heterocyclic and Non‐Heterocyclic Corrosion Inhibitors
5 Amines as Corrosion Inhibitors
5.1 Introduction
5.2 Conclusion and Outlook
References
6 Imidazole and Its Derivatives as Corrosion Inhibitors
6.1 Introduction
6.2 Corrosion Mechanism
6.3 Corrosion Inhibitors
6.4 Corrosion Inhibitors: Imidazole and Its Derivatives
6.5 Computational Studies
6.6 Conclusions
References
7 Pyridine and Its Derivatives as Corrosion Inhibitors
7.1 Introduction
7.2 Summary and Outlook
References
8 Quinoline and Its Derivatives as Corrosion Inhibitors
8.1 Introduction
8.2 Quinoline and Its Derivatives as Corrosion Inhibitors
8.3 Conclusion and Outlook
References
9 Indole and Its Derivatives as Corrosion Inhibitors
9.1 Introduction
9.2 Synthesis of Indoles and Its Derivatives
9.3 A Brief Overview of Corrosion and Corrosion Inhibitors
9.4 Application of Indoles as Corrosion Inhibitors
9.5 Corrosion Inhibition Mechanism of Indoles
9.6 Theoretical Modeling of Indole‐Based Chemical Inhibitors
9.7 Conclusions and Outlook
References
10 Environmentally Sustainable Corrosion Inhibitors in Oil and Gas Industry
10.1 Introduction
10.2 Corrosion in the Oil–Gas Industry
10.3 Review of Literature on Environmentally Sustainable Corrosion Inhibitors
10.4 Conclusions and Outlook
References
Part 3: Organic Green Corrosion Inhibitors
11 Carbohydrates and Their Derivatives as Corrosion Inhibitors
11.1 Introduction
11.2 Glucose‐Based Inhibitors
11.3 Chitosan‐Based Inhibitors
11.4 Inhibition Mechanism of Carbohydrate Inhibitor
11.5 Conclusions
References
12 Amino Acids and Their Derivatives as Corrosion Inhibitors
12.1 Introduction
12.2 Corrosion Inhibitors
12.3 Why There Is Quest to Explore Green Corrosion Inhibitors?
12.4 Amino Acids and Their Derived Compounds: A Better Alternate to the Conventional Toxic Corrosion Inhibitors
12.5 Overview of the Applicability of Amino Acid and Their Derivatives as Corrosion Inhibitors
12.6 Recent Trends and the Future Considerations
12.7 Conclusion
References
13 Chemical Medicines as Corrosion Inhibitors
13.1 Introduction
13.2 Greener Application and Techniques Toward Synthesis and Development of Corrosion Inhibitors
13.3 Types of Chemical Medicine‐Based Corrosion Inhibitors
13.4 Application of Chemical Medicines in Corrosion Inhibition
Acknowledgments
References
14 Ionic Liquids as Corrosion Inhibitors
14.1 Introduction
14.2 Inhibition of Metal Corrosion
14.3 Ionic Liquids as Corrosion Inhibitors
14.4 Conclusion and Future Trends
Acknowledgment
Abbreviations
References
15 Oleochemicals as Corrosion Inhibitors
15.1 Introduction
15.2 Corrosion
15.3 Significance of Green Corrosion Inhibitors
15.4 Overview of Oleochemicals
15.5 Literatures on the Utilization of Oleochemicals as Corrosion Protection
15.6 Conclusions and Outlook
References
Part 4: Organic Compounds‐Based Nanomaterials as Corrosion Inhibitors
16 Carbon Nanotubes as Corrosion Inhibitors
16.1 Introduction
16.2 Characteristics, Preparation, and Applications of CNTs
16.3 CNTs as Corrosion Inhibitors
16.4 Conclusion
Conflict of Interest
Acknowledgment
Abbreviations
References
17 Graphene and Graphene Oxides Layers Application as Corrosion Inhibitors in Protective Coatings
17.1 Introduction
17.2 Preparation of Graphene and Graphene Oxides
17.3 Protective Film and Coating Applications of Graphene
17.4 The Organic Molecules Modified Graphene as Corrosion Inhibitor
17.5 The Effect of Dispersion of Graphene in Epoxy Coatings on Corrosion Resistance
17.6 Challenges of Graphene
17.7 Conclusions and Future Perspectives
References
Part 5: Organic Polymers as Corrosion Inhibitors
18 Natural Polymers as Corrosion Inhibitors
18.1 An Overview of Natural Polymers
18.2 Mucilage and Gums from Plants
18.3 The Future and Application of Natural Polymers in Corrosion Inhibition Studies
References
19 Synthetic Polymers as Corrosion Inhibitors
19.1 Introduction
19.2 General Mechanism of Polymers as Corrosion Inhibitors
19.3 Corrosion Inhibitors – Synthetic Polymers
19.4 Conclusion
References
20 Epoxy Resins and Their Nanocomposites as Anticorrosive Materials
20.1 Introduction
20.2 Characteristic Properties of Epoxy Resins
20.3 Main Commercial Epoxy Resins and Their Syntheses
20.4 Reaction Mechanism of Epoxy/Amine Systems
20.5 Applications of Epoxy Resins
20.6 Conclusion
Abbreviations
References
Index
End User License Agreement
List of Tables
Chapter 5
Table 5.1 Effect of substituents on the corrosion inhibition efficiency of ...
Table 5.2 Chemical structures of some common amides and thio‐amides used as...
Table 5.3 Chemical structures of some common Schiff bases used as corrosion...
Table 5.4 Chemical structures of some common amine‐based drugs and dyes use...
Chapter 6
Table 6.1 Chemical structure of various imidazole derivatives calculated as...
Chapter 7
Table 7.1 A summary of corrosion inhibition effect of some common reports o...
Table 7.2 A summary of corrosion inhibition effect of some common reports o...
Table 7.3 Informations about corrosion inhibition using quinoline derivativ...
Table 7.4 Informations about corrosion inhibition using 8‐hydroxyquinoline ...
Chapter 8
Table 8.1 Chemical structures, abbreviations, and nature of metal and elect...
Table 8.2 Chemical structures, abbreviations, and nature of metal and elect...
Chapter 9
Table 9.1 Indole‐based compounds as corrosion inhibitors for ferrous metals
Table 9.2 Indole‐based alkaloids as corrosion inhibitors of ferrous metal.
Table 9.3 Indole‐based corrosion inhibitors of nonferrous metals
Chapter 12
Table 12.1 Depiction of scientific findings attributable to amino acids as ...
Table 12.2 Illustration of findings of the investigations related to the am...
Table 12.3 Illustration of findings of the investigations related to the am...
Chapter 13
Table 13.1 Names and chemical structure of some drugs used as corrosion inh...
Table 13.2 Names and chemical structure of some expired drugs used as corro...
Chapter 14
Table 14.1 ILs used to inhibit various metal corrosion in HCl medium.
Chapter 15
Table 15.1 Composition of fatty acids in various oils.
Table 15.2 A comparison of literature on the performance of oleochemicals a...
Chapter 16
Table 16.1 Inhibitors, metal/electrolyte, methods applied, and outcomes of ...
Table 16.2 Inhibitors, metal/electrolyte, methods applied, and outcomes of ...
Chapter 18
Table 18.1 Some natural polymers successfully applied to various corrosion ...
Chapter 19
Table 19.1 List of synthetic polymers used as corrosion inhibitor.
Chapter 20
Table 20.1 Abbreviations, nature of metals, electrolytes, adsorption behavi...
Table 20.2 Influence of external inorganic and organic additives on anticor...
List of Illustrations
Chapter 1
Figure 1.1 Corrosion cycle of steel.
Figure 1.2 An electrochemical cell.
Figure 1.3 Mechanism of rust formation.
Figure 1.4 Classified forms of corrosion.
Chapter 2
Figure 2.1 Parameters of single coupon.
Figure 2.2 Different shapes of metal coupons. (a) Strip/rectangular shape co...
Figure 2.3 Presentation of anodic and cathodic Tafel curves and their extrap...
Figure 2.4 The sinusoidal current response in a linear system on application...
Figure 2.5 The making of Lissajous figure.
Figure 2.6 Typical Nyquist plots for a Randles equivalent circuit with C
dl
C...
Figure 2.7 A typical Randles plot.
Figure 2.8 Typical Bode plot.
Figure 2.9 Circuit for linear polarization resistance.
Figure 2.10 Gamma radiography technique for corrosion inspection, (a) tangen...
Figure 2.11 Pictorial presentation of (a) generation of pulse eddy current a...
Figure 2.12 Schematic diagram for generating infrared thermogram.
Chapter 3
Figure 3.1 Periodic boundary condition.
Chapter 4
Figure 4.1 A basic classification of the corrosion inhibitors.
Figure 4.2 The chemical structures of the main azole compounds.
Figure 4.3 The chemical structures of the main azepine compounds.
Figure 4.4 The chemical structures of the main pyridine and azine compounds....
Figure 4.5 The chemical structures of the main indole compounds.
Figure 4.6 The chemical structures of the main quinoline compounds.
Figure 4.7 The chemical structures of the green corrosion inhibitors.
Chapter 6
Scheme 6.1 Resonating structures of imidazole.
Figure 6.1 PDP plots for the corrosion of Al in 0.5M HCl without and with va...
Figure 6.2 Nyquist plots for P110 carbon steel electrode obtained in 1M HCl ...
Figure 6.3 SEM micrographs for (a) blank, (b) M‐1, (c) M‐2, and (d) M‐3.
Figure 6.4 Optimized structures of LMS and PIZ (HOMO/LUMO).
Figure 6.5 Top view and side view of the neutral inhibitors' final adsorptio...
Chapter 7
Figure 7.1 FMOs of benzene, pyridine, 2‐aminopyridine, and 2,6‐diaminopyridi...
Chapter 8
Figure 8.1 Pictorial illustration of some major accidents that have been hap...
Figure 8.2 Classification of organic corrosion inhibitors. Organic corrosion...
Figure 8.3 FMOs (frontier molecular orbitals) pictures of quinoline and 8‐hy...
Chapter 9
Figure 9.1 Structure of indole and isatin. Structures of indole (left‐hand s...
Scheme 9.1 Synthetic scheme of alum catalyzed bis(indolyl)methanes.
Scheme 9.2 One‐pot oxidative Michael reaction of Baylis–Hillman adducts.
Scheme 9.3 Synthetic route of bis‐Schiff bases from isatin.
Scheme 9.4 One‐pot synthesis of indole‐2‐carboxylic acids.
Scheme 9.5 Synthetic scheme of 2‐substituted indoles by heteroannulation.
Scheme 9.6 Preparation of
N
‐benzyl indole aldehydes from indole.
Scheme 9.7 Preparation of 3‐amino‐alkylated indoles.
Scheme 9.8 Synthetic route of Boric acid and CTAB‐catalyzed indole derivativ...
Figure 9.2 Nyquist (a), bode (b), and bode phase (c) spectra for CS obtained...
Figure 9.3 FTIR spectra of BMP powder (a) and the barrier layer of BMP adsor...
Figure 9.4 SEM‐EDX micrographs for polished Cu (a, d), the polished Cu immer...
Figure 9.5 Suggested model of adsorption of bis‐Schiff bases of isatin on MS...
Figure 9.6 Optimized,
E
HOMO
and
E
LUMO
frontier molecular orbitals of neutral...
Figure 9.7 The most stable energy configuration (a) and the density field (b...
Chapter 10
Figure 10.1 Environmentally sustainable inhibitors for oil–gas industry.
Scheme 10.1 Synthesis of chromenopyrazole derivative.
Figure 10.2 Structures of some drugs and drug derivatives as corrosion inhib...
Figure 10.3 Adsorption and corrosion inhibition of Metformin drug on steel s...
Figure 10.4 Structure of some macrocyclic corrosion inhibitors.
Scheme 10.2 Synthesis of chitosan Schiff bases for corrosion inhibition of c...
Scheme 10.3 Synthesis of bis(2‐aminoethyl)amine‐modified GO (B2AA‐GO).
Scheme 10.4 Synthesis of polyethyleneimine‐modified GO (PEI‐GO).
Chapter 11
Figure 11.1 Adsorption model of chitosan Schiff base over the mild steel sur...
Chapter 12
Figure 12.1 A description of the different approaches used to mitigate corro...
Figure 12.2 Outline of the factors that determine the performance of the cor...
Figure 12.3 Some of the commonly investigated green corrosion inhibitors.
Figure 12.4 Amino acids with core asymmetrical carbon to which the amino gro...
Figure 12.5 Outline of the classification of amino acids.
Figure 12.6 Schematic diagram for inorganic–organic core‐shell nanotubes for...
Chapter 13
Scheme 13.1 The simple description of Passerini reaction.
Scheme 13.2 The simple description of Ugi multicomponent reaction.
Scheme 13.3 The general pathway of functionalization of mefenamic acid and n...
Figure 13.1 Molecular structures of some drugs used as corrosion inhibitors....
Chapter 14
Figure 14.1 Industries suffering from corrosion.
Figure 14.2 Different types of ionic liquids.
Figure 14.3 Species that are usually considered as cations and anions for de...
Figure 14.4 Number of papers published on the anticorrosive impact of ILs ve...
Figure 14.5 Constant adsorption configurations of IPyr‐C
2
H
5
and IPyr‐C
4
H
9
mo...
Figure 14.6 Tafel plots of Al utilizing 1M HCl for the process without and w...
Figure 14.7 Synthesis route for the [AAE][Sac] ILs.
Figure 14.8 Tafel curves for mild steel in 1M HCl solution containing differ...
Figure 14.9 Inhibition efficiency of the ILs using AISI 1018 steel in 0.5 an...
Figure 14.10 Synthesis of indolium‐based ionic liquids (IBIL‐V) using standa...
Figure 14.11 Imidazolium ionic liquids.
Chapter 15
Figure 15.1 Production scheme of fatty acid and its derivatives.
Figure 15.2 Various corrosion inhibitors derived from fatty acids.
Scheme 15.1 Synthetic route of palmitic acid imidazole (PI).
Figure 15.3 Schematic of the adsorption of the myristic acid imidazoline on ...
Scheme 15.2 Synthesis of sulfated fatty acid – diethylamine.
Scheme 15.3 Synthesis of imidazole by fatty acid, ethanolamine, and ethanami...
Figure 15.4 Schematic of adsorption of oleic acid hydrazide (OAH) on the elb...
Scheme 15.4 Hydrolysis reaction of crude Palm oil.
Scheme 15.5 Structure of some oleochemical‐based volatile corrosion inhibito...
Scheme 15.6 Structure of oleic hydrazide benzoate and oleic hydrazide salicy...
Scheme 15.7 Synthesis of hydrazides, thiosemicarbazides, oxadiazoles, triazo...
Chapter 16
Figure 16.1 General characteristics of inhibitors.
Figure 16.2 General properties of carbon nanotubes (CNTs).
Figure 16.3 Important applications of carbon nanotubes (CNTs).
Chapter 17
Figure 17.1 Theoretical parameters of graphene.
Figure 17.2 Several common carbon materials.
Figure 17.3 The fabricated N‐doped graphene.
Figure 17.4 The fabricated N‐doped graphene quantum dots.
Figure 17.5 The fabricated processes of graphene oxides.
Figure 17.6 The schematic of (a) protecting to the metal structure and (b) f...
Figure 17.7 The changes of electrochemical potential of the tested samples i...
Figure 17.8 The schematic diagrams of corrosion mechanism for graphene and N...
Figure 17.9 The mechanism of anticorrosion performance of (a) without graphe...
Figure 17.10 Synthetic route of the graphene and waterborne‐epoxy coatings....
Figure 17.11 The self‐repair corrosion‐resistant epoxy film.
Figure 17.12 The anticorrosion mechanism of alkyne‐chain‐modified graphene l...
Figure 17.13 The possible reactions of the modification of graphene oxide wi...
Figure 17.14 Schematic illustration of the preparation of tea polyphenol (TP...
Figure 17.15 The dispersion of graphene and corresponding anticorrosion.
Figure 17.16 Dispersion of graphene in water using g‐C
3
N
4
as dispersant.
Figure 17.17 The polarization curve of nanocomposites coatings after 20 and ...
Chapter 18
Figure 18.1 Sources of naturally occurring natural polymers.
Figure 18.2 Appearance of guar gum.
Figure 18.3 Appearance of acacia gum exudate.
Figure 18.4 Molecular structure of xanthan gum.
Figure 18.5 Basic molecular structure of cellulose.
Figure 18.6 Molecular structures of the amylose (a) and amylopectin (b) mole...
Figure 18.7 Molecular structure of pectate.
Figure 18.8 Molecular structure of chitosan.
Figure 18.9 Molecular structure of carrageenan.
Figure 18.10 Molecular structure of dextrin.
Figure 18.11 Molecular structure of alginate.
Chapter 19
Figure 19.1 Synthesis of BFP polymer.
Figure 19.2 Pictorial representation of mechanism of adsorption of BFP polym...
Figure 19.3 Molecular structures of (a) PDPA‐PDMA‐PMEMA and (b) PDEA‐PDMA‐PM...
Figure 19.4 The synthesis route of polymer.
Chapter 20
Figure 20.1 Epoxy cycle found in polyepoxides.
Figure 20.2 Formation of α‐chlorohydrins.
Figure 20.3 Formation of epoxy rings.
Figure 20.4 Structural formula of the DGEBA – relationship between structure...
Figure 20.5 Synthesis of bisphenol A diglycidyl ether (DGEBA).
Figure 20.6 Degree of hardening as a function of time (s).
Figure 20.7 Chemical structure of CAE.
Figure 20.8 Chemical structure of BISE.
Figure 20.9 Chemical structures of tetra‐functional epoxy resins.
Figure 20.10 Chemical structure of epoxy novolac resins.
Figure 20.11 Chemical structure of DGEBA resin containing CF
3
groups.
Figure 20.12 Chemical structures of epoxy resins containing phosphorus.
Figure 20.13 Chemical structure of PN‐EP.
Figure 20.14 Chemical structures of epoxy resins containing silicon.
Figure 20.15 Chemical structures of epoxy resins containing silicon.
Figure 20.16 Main chemical reactions taking place during cross‐linking.
Figure 20.17 Mechanism of ring opening reaction of epoxy resins in acid solu...
Figure 20.18 Chemical structures of epoxy resins containing diols.
Figure 20.19 Chemical structures of epoxy resins containing amines.
Figure 20.20 Chemical structures of epoxy resins containing phosphorous.
Figure 20.21 Chemical structures of epoxy resins containing 2, 4, 6‐trichlor...
Figure 20.22 Chemical structures of epoxy resins containing glucose derivati...
Guide
Cover Page
Title Page
Copyright Page
Preface
About the Editors
List of Contributors
Table of Contents
Begin Reading
Index
Wiley End User License Agreement
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Organic Corrosion Inhibitors
Synthesis, Characterization, Mechanism, and Applications
Edited by
Chandrabhan Verma
King Fahd University of Petroleum and Minerals
Dhahran, Saudi Arabia
Chaudhery Mustansar Hussain
New Jersey Institute of Technology
Newark, NJ, USA
Eno E. Ebenso
University of South Africa
Johannesburg, South Africa
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Library of Congress Cataloging‐in‐Publication Data
Names: Verma, Chandrabhan, editor. | Hussain, Chaudhery Mustansar, editor. | Ebenso, Eno E., editor.Title: Organic corrosion inhibitors : synthesis, characterization, mechanism, and applications / edited by Chandrabhan Verma, Chaudhery Mustansar Hussain, Eno E. Ebenso.Description: First edition. | Hoboken, NJ : Wiley, 2022. | Includes index.Identifiers: LCCN 2021031915 (print) | LCCN 2021031916 (ebook) | ISBN 9781119794486 (cloth) | ISBN 9781119794493 (adobe pdf) | ISBN 9781119794509 (epub)Subjects: LCSH: Corrosion and anti‐corrosives. | Corrosion and anti‐corrosives–Environmental aspects.Classification: LCC TA462 .O65 2022 (print) | LCC TA462 (ebook) | DDC 620.1/1223–dc23LC record available at https://lccn.loc.gov/2021031915LC ebook record available at https://lccn.loc.gov/2021031916
Cover Design and Image: Wiley
Preface
Corrosion is a highly dangerous phenomenon that causes huge economic and safety problems. Various methods of corrosion monitoring, including cathodic protection, panting and coatings, alloying and dealloying (reduction in metal impurities), surface treatments, and use of corrosion inhibitors have been developed depending upon the nature of metal and environment. Application of organic compounds, especially heterocyclic compounds, is one of the most common, practical, easy, and economic methods of corrosion mitigations. Obviously, these compounds become effective by adsorbing on the metallic surface using electron‐rich centers including multiple bonds and polar functional groups. These electron‐rich centers act as adsorption sites during their interaction with the metallic surface. Along with acting as adsorption sites, the polar functional groups such as –OH (hydroxyl), –NH2 (amino), –OMe (methoxy), –COOH (carboxyl), –NO2 (nitro), –CN (nitrile), and so on also enhance solubility of organic compounds in polar electrolytes. Present book describes the collection of major advancements in using organic compounds as corrosion inhibitors including their synthesis, characterization, and corrosion inhibition mechanism.
Through this book it can be seen that use of organic compounds serves as one of the most effective, economic, and ease methods of corrosion monitoring. Using previously developed methods, 15% (US $375) to 35% (US $875) of cost of corrosion can be minimized. Different series of organic compounds, including heterocyclic compounds, are effectively used as corrosion inhibitors for different metals and alloys in various environments. Because of the increasing ecological awareness and strict environmental regulations, various classes of environmental‐friendly alternatives to the traditional toxic corrosion inhibitors have been developed and being implemented. These series of compounds mostly include carbohydrates, natural polymers and amino acids (AAs), and their derivatives. Corrosion scientists and engineers strongly believe that these environmental‐friendly alternatives will be capable to replace, in the near future, the toxic marketable products that are still being used via many worldwide industries.
A book covering the recent developments on using organic compounds as corrosion inhibitors is broadly overdue. It has been addressed by Drs. Verma, Hussain, and Ebenso in this book which attends to fundamental characteristics of organic corrosion inhibitors, their synthesis and characterization, chronological growths, and their industrial applications. The corrosion inhibition using organic compounds, especially heterocyclic compounds, is broad ranging. This book is divided into five sections, where each section contains several chapters. Section 1 “Basics of corrosion and prevention” describes the basic of corrosion, experimental and computational testing of corrosion, and a comparison between organic and inorganic corrosion inhibitors. Section 2 “Heterocyclic and non‐heterocyclic corrosion inhibitors” describes the collection of different series of heterocyclic and non‐heterocyclic corrosion inhibitors such as amines, imidazole, quinoline, pyridine, indole, and their derivatives. This section also includes organic compounds as corrosion inhibitors for oil and gas industries.
Section 3 “Organic green corrosion inhibitors” entirely focuses on green corrosion inhibitors. This section describes the corrosion inhibition characteristics of carbohydrates, amino acids (AAs), oleochemicals, chemical medicines, ionic liquids (ILs), and their derivatives. Section 4 “Organic compounds based nanomaterials as corrosion inhibitors” describes the corrosion inhibition properties of carbon nanotubes (CNTs: SWCNTs and MWCNTs), graphene oxide (GO), and their composites. In the end, Section 5 “Organic polymers as corrosion inhibitors” gives a description on natural and synthetic polymers as corrosion inhibitors.
Overall, this book is written for scholars in academia and industry, working corrosion engineering, materials science students, and applied chemistry. The editors and contributors are well‐known researchers, scientists, and true professionals from academia and industry. On behalf of Wiley, we are very thankful to authors of all chapters for their amazing and passionate efforts in making of this book. Special thanks to Prof. M. A. Quraishi, who guided us continuously in drafting of this book. Special thanks to Michael Leventhal (acquisitions editor) and Katrina Maceda (managing editor) for their dedicated support and help during this project. In the end, all thanks to Wiley for publishing the book.
Chandrabhan Verma, PhD
Chaudhery Mustansar Hussain, PhD
Eno E. Ebenso, PhD
About the Editors
Chandrabhan Verma
Chandrabhan Verma is working at the Interdisciplinary Center for Research in Advanced Materials King Fahd University of Petroleum and Minerals (KFUPM), Saudi Arabia. He obtained his PhD in Corrosion Science at the Department of Chemistry, Indian Institute of Technology (Banaras Hindu University) Varanasi, India. He is a member of American Chemical Society (ACS). His research is mainly focused on the synthesis and designing of environmental friendly corrosion inhibitors useful for various industrial applications. Dr. Verma is the author of several research and review articles published in the peer‐reviewed international journals of ACS, Elsevier, RSC, Wiley, Springer, etc. He has total citation of more than 4700 with H‐index of 39 and i10‐index of 91. Dr. Verma received several national and international awards for his academic achievements.Chaudhery Mustansar Hussain, PhD, is an adjunct professor and director of labs in the Department of Chemistry & Environmental Sciences at the New Jersey Institute of Technology (NJIT), Newark, New Jersey, USA. His research is focused on the applications of nanotechnology & advanced technologies & materials, analytical chemistry, environmental management, and various industries. Dr. Hussain is the author of numerous papers in peer‐reviewed journals, as well as prolific author and editor of several scientific monographs and handbooks in his research areas published with Elsevier, Royal Society of Chemistry, John Wiley & sons, CRC, Springer, etc.
Chaudhery Mustansar Hussain
Eno E. Ebenso is a research professor at the Institute of Nanotechnology and Water Sustainability in the College of Science, Engineering and Technology, University of South Africa. He has published extensively in local and international peer‐reviewed journals of wide readership with over 300 publications (articles in newspapers, plenary/invited lectures, and conference proceedings not included). He currently has an H‐Index of 67 and over 10 000 total citations from the Scopus Search Engine of Elsevier Science since 1996. According to the Elsevier SciVal Insights Report (2010–2015), he has a citation impact 10% above world average: second most prolific author in the field of corrosion inhibition worldwide and fifth most downloads of his publications globally in the field of corrosion inhibition. His Google Scholar Citations since 2013 is over 8000 with an H‐index of 64 and i10‐index of 216. His RESEARCHERID account shows H‐index of 44 with total citations of 5779 and average citation per article of 24.78. He is also a B3 NRF Rated Scientist in Chemistry (South African National Research Foundation). INTERPRETATION – B3: Most of the reviewers are convinced that he enjoys considerable international recognition for the high quality and impact of his recent research outputs. He is a member of International Society of Electrochemistry, South African Chemical Institute (M.S.A. Chem. I.), South African Council for Natural Scientific Professions (SACNASP) (Pri. Sci. Nat.), Academy of Science of South Africa (ASSAf), and a fellow of the Royal Society of Chemistry, UK (FRSC).
Eno E. Ebenso
List of Contributors
Ekemini D. AkpanDepartment of ChemistrySchool of Chemical and Physical Sciences and Material Science Innovation & Modelling (MaSIM) Research Focus AreaFaculty of Natural and Agricultural SciencesNorth‐West UniversityMmabatho, South Africa
Mustafa R. Al‐HadeethiDepartment of ChemistryCollege of EducationKirkuk UniversityKirkuk, Iraq
F. A. AnsariDepartment of Applied SciencesFaculty of EngineeringJahangirabad Institute of TechnologyBarabanki, India
Jeenat AslamDepartment of ChemistryCollege of ScienceTaibah UniversityYanbu, Al‐MadinaSaudi Arabia
Ruby AslamCorrosion Research Laboratory, Department of Applied ChemistryFaculty of Engineering and TechnologyAligarh Muslim UniversityAligarhUttar PradeshIndia
Megha BasikCorrosion Research LaboratoryDepartment of Applied ChemistryFaculty of Engineering and TechnologyAligarh Muslim UniversityAligarhUttar PradeshIndia
Abdelkarim ChaouikiLaboratory of Applied Chemistry and EnvironmentENSAUniversity Ibn ZohrAgadirMorocco
Dheeraj Singh ChauhanCenter of Research Excellence in CorrosionResearch InstituteKing Fahd University of Petroleum and MineralsDhahranSaudi ArabiaModern National ChemicalsSecond Industrial CityDammamSaudi Arabia
Omar DagdagLaboratory of Industrial Technologies and Services (LITS)Department of Process EngineeringHeight School of TechnologySidi Mohammed Ben Abdallah UniversityFezMorocco
Amit Kumar DewanganDepartment of ChemistryGovernment Digvijay Autonomous Postgraduate CollegeRajnandgaonChhattisgarhIndia
Yeestdev DewanganDepartment of ChemistryGovernment Digvijay Autonomous Postgraduate CollegeRajnandgaonChhattisgarhIndia
Eno E. EbensoInstitute for Nanotechnology and Water SustainabilityCollege of Science Engineering and TechnologyUniversity of South AfricaJohannesburgSouth Africa
M. El GouriLaboratory of Industrial Technologies and Services (LITS)Department of Process EngineeringHeight School of TechnologySidi Mohammed Ben Abdallah UniversityFez, Morocco
Lei GuoSchool of Material and Chemical EngineeringTongren UniversityTongrenPeople’s Republic of China
Rajesh HaldharSchool of Chemical EngineeringYeungnam UniversityGyeongsanSouth Korea
A. El HarfiLaboratory of Advanced Materials and Process EngineeringDepartment of ChemistryFaculty of SciencesIbn Tofaïl UniversityKenitra, Morocco
Jiyaul HaqueDepartment of ChemistryIndian Institute of TechnologyBanaras Hindu UniversityVaranasiIndia
Zhongyi HeSchool of Materials Science and EngineeringEast China JiaoTong UniversityNanchangPeople’s Republic of China
Chaudhery Mustansar HussainDepartment of Chemistry and Environmental ScienceNew Jersey Institute of TechnologyNewarkNJUSA
Savaş KayaHealth Services Vocational SchoolDepartment of PharmacySivas Cumhuriyet UniversitySivasTurkey
Hassane LgazDepartment of Architectural EngineeringHanyang University‐ERICAAnsanKorea
Han‐Seung LeeDepartment of Architectural EngineeringHanyang University‐ERICAAnsanKorea
Lukman O. OlasunkanmiDepartment of ChemistryFaculty of ScienceObafemi Awolowo UniversityIle IfeNigeria
Marziya RizviCorrosion Research LaboratoryDepartment of Mechanical EngineeringFaculty of EngineeringDuzce UniversityDuzceTurkey
Sheerin MasroorDepartment of ChemistryA.N. CollegePatliputra UniversityPatna India
Mohammad MobinCorrosion Research LaboratoryDepartment of Applied ChemistryFaculty of Engineering and TechnologyAligarh Muslim UniversityAligarhUttar PradeshIndia
Rachid SalghiLaboratory of Applied Chemistry and EnvironmentENSAUniversity Ibn ZohrAgadirMorocco
Goncagül SerdaroğluFaculty of EducationDepartment of Mathematics and Science EducationSivas Cumhuriyet UniversitySivasTurkey
ShobhaDepartment of PhysicsBanasthali VidyapithVanasthaliRajasthanIndia
SudheerDepartment of ChemistryFaculty of Engineering and TechnologySRM‐Institute of Science and TechnologyGhaziabadIndia
M. A. QuraishiInterdisciplinary Research Center for Advanced MaterialsKing Fahd University of Petroleum and MineralsDhahranSaudi Arabia
Taiwo W. QuadriDepartment of ChemistrySchool of Chemical and Physical Sciences and Material Science Innovation & Modelling (MaSIM) Research Focus AreaFaculty of Natural and Agricultural SciencesNorth‐West UniversityMmabatho, South Africa
Chandrabhan VermaInterdisciplinary Research Center for Advanced MaterialsKing Fahd University of Petroleum and MineralsDhahranSaudi Arabia
Dakeshwar Kumar VermaDepartment of ChemistryGovernment Digvijay Autonomous Postgraduate CollegeRajnandgaonChhattisgarhIndia
Xue YangSchool of Materials Science and EngineeringEast China JiaoTong UniversityNanchangPeople’s Republic of China
Saman ZehraCorrosion Research LaboratoryDepartment of Applied ChemistryFaculty of Engineering and TechnologyAligarh Muslim UniversityAligarhUttar PradeshIndia
Renhui ZhangSchool of Materials Science and EngineeringEast China JiaoTong UniversityNanchangPeople’s Republic of China
Part 1Basics of Corrosion and Prevention
1An Overview of Corrosion
Marziya Rizvi
Corrosion Research Laboratory, Department of Mechanical Engineering, Faculty of Engineering, Duzce University, Duzce, Turkey
1 Introduction
1.1 Basics About Corrosion
Corrosion can be scientifically defined in many ways. The term “corrode” is itself obtained from the Latin word “corrodere,” i.e. “to gnaw to pieces.” The National Association of Corrosion Engineers (NACE) has defined it: “Corrosion is a naturally occurring phenomenon commonly defined as the deterioration of a material (usually a metal) that results from a chemical or electrochemical reaction with its environment” [1]. International Standard Organization explains “corrosion” technically as the “Physio‐chemical interaction between a metal and its environment which results in changes in the properties of the metal and which may often lead to impairment of the function of the metal, the environment or the technical system of which these forms a part” [2]. The environment is basically all that present surrounding and in contact with the observed metal/material. The primary factors describing the environment are (i) physical state (gas/liquid/solid); (iii) chemical composition (constituents &concentrations); and (c) the temperature. The corroded metal has obtained a thermodynamic stability in changing to oxides, hydroxides, salts, and carbonates. As per law of entropy, metals post fabrication return to their lowest energy, or natural ore form. Naturally metals are found in their element form or as ores. A lot is incorporated to convert iron ore into steel in the steel factories (Figure 1.1).
Figure 1.1 Corrosion cycle of steel.
Corrosion is the just reverse of what is known as extractive metallurgy. That implies that the energy utilized to convert an ore into a pure metal is reversed on exposure to environment (oxygen and water). On the exposed metal, oxides, sulfates, and carbonates exist [3–4]. Corrosion science as a subject has been around for many years in the textbooks, and surely its relevance has increased now. Education of corrosion and corrosion mitigation makes the environment safer and more sustainable.
1.2 Economic and Social Aspect of Corrosion
The incurred monetary losses and negative effects on environment geared the current ad on‐going researches in the field of corrosion. To sum up the total monetary loss due to corrosion, cost studies have been carried out in several countries. The first significant work on cost of corrosion was presented as a report by Uhlig in 1949, estimating the annual cost of corrosion as US$5.5 billion [5]. However, comprehensively the first study on losses incurred due to corrosion was conducted in the United States in late 1970s. In the year 1978, US$70 billion were wasted, equivalent to approximately 5% of gross national product (GNP) of that year [6]. The US Federal Highway Administration (FHWA) published a breakthrough study back in 2002, estimating the direct corrosion cost associated with USA’s industrial sector. The study was conducted by NACE International initiated the study as part of Transportation Equity Act for the 21st Century (TEA‐21), having a Congress mandate. The estimated direct cost of corrosion annually is $276 billion, which implies GNP’s 3.1% [7]. This estimation is solely inclusive of the direct costs pertaining to maintenance. Other expenditures after production loss, negative environmental effect, disrupted transports, fatalities, and injuries were computed to be as much as the direct costs. Similarly, some countries conducted corrosion cost studies. These countries were Australia, United Kingdom, Japan, Germany, Kuwait, Finland, India, China, and Sweden. It was inferred that annual corrosion costs was 1–5% of the national GNPs. The recently published material relates the global economic losses due to corrosion, summed up by NACE International in 2016 as $2.5 trillion, which is 3.5% of global GDP [8–10]. The Central Electrochemical Research Institute calculated the cost of corrosion in India by NBS input/output economic model for 2011–2012. The direct cost was US$26.1 billion or 2.4% GDP. The cost avoidable was US$9.3 billion or 35% direct cost of corrosion. The indirect cost was US$39.8 billion or 3.6% of IGDP [11]. NACE International according to the latest global studies estimated Indian cost of corrosion to be GDP’s 4.2% [12]. Beyond the cost of corrosion financially are the indirect costs like loss of opportunities and natural resources, potential hazards, etc. A project constructed using building material unable to withstand its environment for the estimated design life, the l resources are being needlessly consumed at later stages for maintenance and repair. Wasting the already depleting natural resources is a direct opposition to the increasing emphasis and demand for sustainable development in order to safeguard for future generations. Along with the wastage of natural resources, weak constructed structures pose threat to lives and well‐being. Huge safety concerns have been established in regards with the accidents that might happen in case of corroding structures. A single pipeline that fails, a bridge that collapses, a derailed train compartment due to corroded track, or other accidents is one among numerous that cause enormous indirect losses and huge public outcry. According to the market sector considered, the indirect losses might make up to 5–10 times the direct loss.
1.3 The Corrosion Mechanism
Corrosion occurs by formation of an electrochemical/corrosion cell (Figure 1.2).
This particular electrochemical cell comprises of five parts.
Anodic zones
Cathodic zones
Electrical contact between these zones
An electrolyte
A cathodic reactant
Inside this electrochemical cell, electrons depart from anodic to cathodic sites. The charged particles, ions, move across the conducting solution to balance the electrons flow. Anions (from cathodic reactions) move toward the anode and cations (from the anode itself) drift toward the cathode. Resultantly, anode corrodes and the cathode does not. There also exists a voltage/potential difference amidst anode and cathode. Numerous discrete micro cells develop on the metal surfaces, due to the constitutional phase difference, from stress variations, coatings, and imperfection levels like dislocations, grain boundaries, kink sites, or from ionic conductivity alterations or compositional changes in the conducting solution. The corrosion process is chemically spontaneous oxidation of the metal on reaction with the cathodic reactant. Every similar cell reaction results from a pair of simultaneous anodic and cathodic reactions going on at identical rates on the surface of metal.
Figure 1.2 An electrochemical cell.
1.3.1 Anodic Reaction
At the anode, the metal corrodes. The anodic reaction is the oxidation of a metal to its ionic form when the electric charge difference exists at the solid–liquid interface. Generally, anodic reaction is an oxidation reaction of a metal to its metal ions, which passes into conductive solution:
where “n” is the metallic valence, e− is the electron, M is metal, and Mn+ its metalion.
1.3.2 Cathodic Reactions
The cathodic reaction involves the environment and can be represented by the following reaction:
where R+ is the positive ion present in the electrolyte, e− is the metallic electron, and R0 is the reduced species. Based on the environment, many cathodic reactions and electron consuming reactions are possible. The main reactions are as follows.
The anaerobic acidic aqueous environment
In the anaerobic alkaline aqueous environment
In the aerobic acidic aqueous environment
In the aerobic alkaline aqueous environment
Some other reactions that are most commonly present in the chemical process are following.
Metal ion reduction
Metal ion deposition
The products of the anodic and cathodic reactions react to form solid corrosion products on the surface of the metal. The Fe2+ interacts with OH− ions as:‐
Fe(OH)2 is reoxidized to Fe(OH)3, an unstable product, and thus transforms to hydrated ferric oxide commonly called as red rust (Figure 1.3).
Figure 1.3 Mechanism of rust formation.
Figure 1.4 Classified forms of corrosion.
1.4 Classification of Corrosion
Seldom is a single class of corrosion discovered in corroding structures. Different metals in contact and contact with different environment hardly allow only one type of corrosion to occur even within a system. Each type of corrosion is caused by their specific reaction mechanisms and has their specific monitoring, prediction, and control methods. Figure 1.4 throws some light on classification of corrosion in a pictorial manner. None of the classifications is a universal standard, even the following classification is an adapted [4, 13].
1.4.1 Uniform Corrosion
This type of corrosion affects a large patch over the metal and causes overall reduction of metallic thickness subject to the fact that metal undergoing corrosion has a uniform composition and metallurgy too. What happens is that anode and cathode do not possess fixed sites; as such there are no sites preferable to corrosion, which occurs here in a uniform fashion. Corrosion rates are easily monitored by electrochemical measuring techniques or gravimetric analysis. A metal suffering from uniform corrosion can be protected using corrosion inhibitors or coatings and also by cathodic protection. Atmospheric corrosion is an example of uniform corrosion. When exposed to dry atmospheres with very less humidity, metals spontaneously tend to form an oxide film. This barrier oxide film acquires a thickness of 2–5 nm [14].
1.4.2 Pitting Corrosion
Pitting corrosion is highly destructive form and a kind of localized attack, which leads to little holes called pits in metal. Small cavities and holes, which are as deep as their diameter, are known as pits. They cause perforations by penetrating into the metal with least loss of weight [15]. Pitting is proportional to the logarithm of electrolyte’s concentration of chloride. The prerequisite for pitting to occur is that the electrolyte should be a strong oxidizer for onset of the passive state. The ferric and cupric halide ions are electron acceptors (cathodic reactants), and they do not need oxygen to initiate and propagate pitting. Other propagating factors causing pitting include localized damage chemically and mechanically to a passive oxide film, non‐metallic impurities/non‐uniformities of metal structure due to nonproportional inhibitor coverage. Pitting, however, can be evaded by reducing aggressiveness of the solution, decreasing the temperature of conductive solution, decreasing Cl− concentration and acidity.
1.4.3 Crevice Corrosion
It is also localized version of corrosion on a microenvironment level but related to a stagnant electrolyte caused by gasket surfaces, lap joints and holes, crevices under bolts, rivet heads, and surface deposits. To evade and limit this type of corrosion, it is suggested to (i) use of welds instead of bolt/rivet joints, (ii) a design to ensure complete draining, (iii) hydrofuging any interstices, which cannot be removed, and (iv) utilizing solely solid and nonporous seals, etc.
1.4.4 Galvanic Corrosion
This type of corrosion is also called “bimetallic corrosion” and “dissimilar metal corrosion,” because it occurs due to electrical contact with a more noble metal or maybe a nonmetallic conductor in the electrolyte. The active member of the metallic couple, i.e. less corrosion resistant bears an accelerated corrosion rate, while the noble member is protected by the cathodic effect. The joint between the metals is most corrosion affected. Moving away from this junction, the corrosive attack reduces. As it is already known that each metal has its unique corrosion potential in an electrolyte, the potential difference between the two dissimilar metals causes the less noble metal to corrode. To estimate the corrosion rate conductivity of metal and electrolyte, potential difference of relative anodic and cathodic areas might be accounted [16–18]. To prevent such an attack, the metals should lie close by on the electrochemical series, comparably area of anode should not be too small; if different metals are involved, insulation must be applied; and coatings, paints, and avoiding thread joints are good preventive measures.
1.4.5 Intergranular Corrosion
This corrosion can be referred to as “intercrystalline corrosion”/“interdendritic corrosion” as tensile stress causes it along the grain or crystal boundaries. It might also be known as “intergranular stress corrosion cracking” and “intergranular corrosion cracking.” These corrosive attack prefers interdendritic paths. A microstructure examination using a microscope is needed for recognizing this degradation; however, at times, it is recognizable with eyes as in weld decay. The composition’s local differences like coring in alloy castings lead to this type of corrosion. The mechanism includes precipitation in grain boundaries like in the case of precipitating chromium carbides in steel. Intermetallic segregation at grain boundaries in aluminum is called “exfoliation.” This corrosion type might be prevented and controlled by using mild steel, low carbon type like using post‐weld treatment, etc.
1.4.6 Stress‐Corrosion Cracking (SCC)
Such a cracking occurs by the simultaneous action of a corrodent and sustained tensile stress. This bars the corrosion‐less sections, intercrystalline or trans‐crystalline corrosion, which might destroy an alloy without any stress. It is accompanied with hydrogen embrittlement. It might be a conjoint action of a susceptible material, a specific chemical species, and tensile stress. Sedriks and Turnbull reviewed the standard SCC testing [19–20]. Time‐consuming techniques, bulky specimens, and expensiveness limit the usage of SCC monitoring techniques. Stress corrosion cracking might be prevented by avoiding chemical species that causes it, controlling hardness and stress, using un‐crackable materials specific to environment and temperature/potential control of operation.
1.4.7 Filiform Corrosion
On steel, aluminum, aircraft structures in humidity, flanges, beverage cans, gaskets, and weld zones, this type of corrosion can be detected. Irregular hairlines, sometimes corrosion products filaments present below coatings of paint, rubber, lacquer, tin, silver, enamel, and paper, develop. Material is not lost significantly, but the surface deteriorates. Copper, stainless steel, and titanium alloys are unsusceptible to this attack.
1.4.8 Erosion Corrosion
Rapidly flowing electrolyte and turbulence cause erosion of the metal. The main culprits for turbulence are the pits within a pipeline. Turbulence finally causes a pipeline to have leakage. The velocity of the flowing electrolyte and the physical action of it moving against the surface causes metallic loss at an accelerated rate. Erosion is common occurrence in constriction areas like pump impellers and inlet ends. Erosion can be tackled by less turbulent fluid movement, low velocity of flow, using corrosion resistant pipeline materials, inhibitors, etc.
1.4.9 Fretting Corrosion
A slight oscillatory slip between two surfaces in contact causes fretting corrosion. Bolted/riveted parts are made such that they do not slip or oscillate, which fails in the presence of fluctuation of pressure and vibration. Fretting can be prevented by regular inspection and maintenance of the lubrication.
1.4.10 Exfoliation
At the elongated grain boundaries, the corrosion products present cause the metal to be forced away from the material and form layer‐like look, and this is called exfoliation. Also known as lamellar, layered, and stratified corrosion, it proceeds along selected subsurfaces. If the grain boundary attack is severe, it is visible; otherwise a microscope conducts the microstructure examination. Alloys of aluminum are most susceptible to exfoliation. This can be controlled using coatings, heat treatment to control precipitate distribution, and exfoliation‐resistant aluminum alloy.
1.4.11 Dealloying
Dealloying is selective corrosion of solid solution of alloy also known as leaching/selective attack/parting. Dealloying can be manifested in various categories like decobaltification (selective leaching of cobalt from cobalt‐base alloys), decarburization (selective loss of carbon from the surface layer), dezincification (selective leaching of zinc from zinc‐containing alloys), denickelification (selective leaching of nickel from nickel‐containing alloys), and graphitic corrosion (gray cast iron in which the metallic constituents are selectively leached). Dealloying might be prevented by selecting more resistant alloys, controlling the selective leaching, sacrificial anode/cathodic protection.
1.4.12 Corrosion Fatigue
Corrosion and cyclic stress when occur simultaneously result in cracks. This is corrosion fatigue. Rapidly fluctuating stress below the tensile strength usually are causative agents. The metallic fatigue strength decreases in corrosive electrolyte. It can be prevented by using high‐performance alloys resistant to corrosion fatigue and by using coatings and inhibitors delaying the crack initiation.
1.5 Common Methods of Corrosion Control
Corrosion control is applying the principles of engineering to limit corrosion economically. Each preventive measure bears its own complexities and specificity. Basically, the idea is to detect the mechanism and causative agents of the degradation and reduce them or completely prevent them from occurring. Let us have a look on some of them as given below.
1.5.1 Materials Selection and Design
There is no all‐noble and completely corrosion‐resistant metal, but a careful selection might increase the longevity of the metal component. Factors influencing the materials selection are resistance to degradation, test data and design availability, cost, mechanical properties, availability, compatibility with other components, maintainability, life expectancy, appearance, and reliability. Availability, inexpensiveness, and easy fabrication make carbon steel a favorable material for selection [21]. In the petrochemical plants, highly corrosive catalysts and solvents are usually encountered, so stainless steel is best option [22]. Duplex stainless steels are used in pressure vessels, storage tanks, and heat exchangers owing to their good mechanical properties, high resistance to chloride stress corrosion cracking, good erosion and wear resistance, and low thermal expansion [23]. For seawater service, duplex stainless steels of higher molybdenum content (e.g. Zeron 100) have been developed [24]. Appropriate system design is crucial for efficient corrosion control. Numerous factors like materials selection, geometry for drainage, process and construction parameters, avoiding or sealing of crevices, avoidance or electrical separation of dissimilar metals, operating lifetime, and maintenance and inspection requirements are involved.
1.5.2 Coatings
Coatings are generally good option to insulate the metals from exterior aggressive environments. They extend a lengthy protection in wider spectrum of corrosive conditions, atmospheric to aqueous electrolyte solution. Although they provide no structural strength, yet they protect the strength and integrity of a structure. Their function is that of a physical barrier preventing electrolytic attack on metal. Organic coatings like paints, resins, lacquers, and varnishes are the most popular protective coatings. Metallic coating (noble or cathodic and sacrificial or anodic) is also used for corrosion control.
1.5.3 Cathodic Protection (CP)
A metal is completely converted to a cathode to protect it against corrosion. CP is implemented by driving the potential to a negative region/stabilized metal region. Either an external power supply changes the amount of charge on the metal surface or a more reactive metal is converted to a sacrificial anode. The principle involved in CP is to potentially let the metallic article or structure attain corrosion immunity. A stable and unreactive metal is impossible to corrode. This method might be expensive as electricity is consumed, and the extra metals are involved. Cathodic protection can be attained by coupling a given structure (like Fe) with a reactive metal like zinc or magnesium or by impressing a direct current between an inert anode and the metal to be immunized.
1.5.4 Anodic Protection
Based on phenomenon of passivity, anodic protection can control the corrosion in an electrochemical cell. Metal is kept in a passive state; surface is connected as an anode to an inert cathode in the corrosion cell. Anodic protection is used to protect metals that exhibit passivation in environments; when the current density in a corroding structure is much higher than the current density of the same in its passive state over a wide range of potentials, anodic protection can be used. This preventive measure is adopted in aerospace and other critical applications and wherever the cathodic protection is not cost‐effective.
1.5.5 Corrosion Inhibitors
The most prevalent, economic, and effective measure against corrosion of metallic surfaces in aggressive media in closed systems is inhibitors [25–30]. Corrosion inhibitors are added in small concentration to effectively reduce the corrosion rate of a metal exposed to corrosive solution. It is similar to a retarding catalyst, which reduces the corrosion rate by increasing or decreasing the reaction of anode and/or cathode, decreasing the reactants’ diffusion rate to the metallic surface and decreasing the metallic surface’s electrical resistance. Without disrupting the setup, inhibitors can be added in situ. Adsorption theory best explains their functioning in a corrosion cell. Adsorption refers to the adhesion of a chemical species to the superficial single monolayer of the metal without bonding with the bulk of metal. The type of the corrosion medium, the magnitude of the charge at the metal/solution interface, the nature of metal, and the cathodic reaction decide the inhibitor. Three types of environments use inhibitors, namely, recirculating cooling water systems in the pH range of 5–9, primary and secondary production of crude oil and pickling acid solution for the removal of dust and mill scale during the production and fabrication of metals parts, or also for the post‐service cleaning. Based on their composition or mechanism of protection, inhibitors are classified as follows.
1.6 Adsorption Type Corrosion Inhibitors
As the name suggests, these organic compounds adsorb on the metal to suppress dissolution and the reduction reaction. Adsorption inhibitors affect both anodic and cathodic process equally or disproportionally.
Vapor‐phase corrosion inhibitors
Vapor‐phase corrosion inhibitors also called volatile corrosion inhibitors. The vapor pressure of these compounds at 20–25°C is usually between 0.1 and 1.0 mm Hg. When kept in the vicinity of the metal to be protected, they sublime and condense in enclosed spaces [31]. For example, phenylthiourea and cyclohexylamine chromate are used for protecting brass. Dicyclohexylamine nitrite protects both ferrous and nonferrous metals/alloys.
Inorganic inhibitors
Some metal ions like Pb2+, Mn2+, and Cd2+ deposit on the iron surface in acidic environment [32]. Even Br− and I− inhibit corrosion in strongly acidic solutions [33]. As2O3 and Sb2O3are also corrosion inhibitors in acidic media. These substances form a metal oxide layer and increase the hydrogen over‐voltage to reduce the corrosion rate.
Organic inhibitors
It includes large number of organic substances containing N, S, or O atoms in the molecule. Organic inhibitors possess a functional group as the reaction center for the adsorption process. They have heteroatoms like N, S, and O in their structures. The molecular structures majorly influence the extent of inhibition of corrosion.
1.6.1 Anodic Inhibitors
Those substances that reduce the anodic area by acting on the anodic sites and polarizing the anodic reaction are called anodic inhibitors [34]. Anodic inhibitors cause displacements in corrosion potential in positive direction, suppress corrosion current, and reduces corrosion rate. If an anodic inhibitor is not present at a concentration level sufficient to block off all the anodic sites, localized attack such as pitting corrosion can become a serious problem due to the oxidizing nature of the inhibitor, which raises the metal potential and encourages the anodic reaction. Anodic inhibitors are classified as unsafe because they may cause localized corrosion. Examples of anodic inhibitors include orthophosphate, chromate, nitrite, ferricyanide, and silicates.
1.6.2 Cathodic Inhibitors
There are substances that may lessen the cathodic area by polarizing the cathodic reactions on cathodic area [35]. Cathodic inhibitors transfer the corrosion potential in negative direction to retard cathodic reaction and suppress the corrosion rate. Cathodic area is reduced by precipitating the insoluble species on cathodic sites. Cathodic inhibitors do not cause localized corrosion hence safe. They are cathodic poisons/hydrogen‐evolution poisons like arsenic and antimony ions. Scavengers like sodium sulfite and hydrazine are filming inhibitors (cathodic precipitates).
1.6.3 Mixed Inhibitors
The formulation contains more than one inhibitor in this case. These inhibitors interfere with anodic, as well as cathodic reactions. These inhibitors are used for multi‐metallic substrates and when combined and optimized cathodic/anodic effect is required. The halide ions enhance the action of organic inhibitor in acid solutions.
