Smart Protective Coatings for Corrosion Control E-Book

Lingwei Ma

• Herausgeber: Wiley-VCH GmbH
• Kategorie: Fachliteratur
• Sprache: Englisch
• Veröffentlichungsjahr: 2024

Seitenzahl: 843

Beschreibung

Gives an overview of the state of the art of advanced coatings for anticorrosion

Das E-Book Smart Protective Coatings for Corrosion Control wird angeboten von Wiley-VCH GmbH und wurde mit folgenden Begriffen kategorisiert:
Beschichtung, Chemie, Chemistry, Corrosion, Dünne Schichten, Oberflächen u. Grenzflächen, Electrochemistry, Elektrochemie, Korrosion, Korrosionsschutz, Materials Science, Materialwissenschaften, Thin Films, Surfaces & Interfaces

Leseprobe

Smart Protective Coatings for Corrosion Control

Lingwei Ma and Dawei Zhang

Authors

Prof. Lingwei MaUniversity of Science and Technology BeijingBeijing, 100083China

Prof. Dawei ZhangUniversity of Science and Technology BeijingBeijing, 100083China

Cover Image: © Oleg Breslavtsev/Getty Images

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Print ISBN: 978‐3‐527‐35386‐6ePDF ISBN: 978‐3‐527‐84714‐3ePub ISBN: 978‐3‐527‐84713‐6oBook ISBN: 978‐3‐527‐84715‐0

Foreword

Corrosion represents natural and gradual deterioration of materials (usually metals) by chemical or electrochemical interaction with their environment. This process jeopardizes functional and structural integrity in equipment and infrastructure, shortens their operational lifespan, and ultimately may trigger catastrophic failures and environmental contamination, imposing grave threats to public safety and property. It is universally acknowledged that corrosion is a global issue, affecting our buildings, roads, machinery, bridges, vessels, and any locale where materials are exposed to industrial or natural corrosive environments, including atmospheric moisture, salts, alkalis, acids, and diverse chemical agents. Authoritative data indicate that the economic losses due to corrosion amount to 3–5% of the gross domestic product (GDP) in many industrialized countries. Like earthquakes, fires, and pollution, corrosion poses a serious hazard, rendering the onus of corrosion mitigation paramount.

To minimize the functional and structural impact caused by corrosion, the application of corrosion protection coatings emerges as one of the most effective methods to inhibit material corrosion degradation and reduce economic losses. Such coatings can slow down the rate of material corrosion under exposure to aggressive environmental conditions, thereby extending the service life of the object. In ancient times, substances such as egg whites, tree gums, and asphalt served as coating materials, providing a physicochemical barrier between the environment and the underlying metal. Nowadays, engineers can integrate functionality and aesthetics into coating designs using polymer technology and nanotechnology. In modern society, nearly all man‐made items employ protective or decorative coatings, with the global coatings industry generating approximately one trillion US dollars in annual production. With continuous industrial development and the need for applications exposed to extreme conditions, the performance specifications for corrosion protection coatings have escalated, leading to the emergence of smart coatings distinguished by eco‐friendliness, self‐cleaning, self‐healing, corrosion sensing, and enhanced durability. Combining new smart coating technologies with traditional methodologies, or using smart coatings to replace traditional ones, has emerged as one of the focal points of research topics in preventing metal corrosion.

This book comprehensively and systematically introduces the latest advancements and future prospects of smart coatings. It elaborates on the raw materials, preparation methods, corrosion prevention principles, and monitoring technologies used for each category of smart coatings. It is a valuable resource summarizing the currently achieved performance level and further development status of smart coating technologies. The smart coating technologies and corrosion monitoring methods presented in this book will have a favorable effect on improving the service life of coatings in complex and aggressive service environments. This publication is a timely compendium, serving as a pivotal reference for scholars and engineers across a wide variety of backgrounds, providing theoretical support for the innovation of new coatings in the corrosion protection engineering field, and acting as a technical guide for professionals in industry. It guides the conceptualization and design of state‐of‐the‐art technologies for intelligent corrosion control through theoretical insights and practical examples, which has profound implications for the transformation toward a sustainable industry and circular economy. I also hope that this book will inspire a broader audience to engage with the development of corrosion protection technology, enhance comprehension and awareness of corrosion issues and corrosion protection strategies in various industries, and contribute to addressing the global material and energy transition challenges.

TU Delft, The Netherlands29 February 2024

Arjan Mol

Preface

Corrosion refers to the degradation and deterioration of metals owing to chemical, electrochemical, or other reactions at the surface or interface. This process damages engineering structures, which shortens their service life, increases the maintenance cost, and causes accidents that threaten the environment and public safety. In terms of magnitude, it was estimated that almost one ton of steel is converted to rust every minute around the world. Each year, up to one‐third of global steel production is scrapped owing to corrosion, approximately one‐third of which is irrecoverable. The annual economic loss due to corrosion far exceeds that due to natural disasters and other accidents: the global economic loss due to corrosion amounts to approximately US$4 trillion per year, with China's annual economic loss from corrosion estimated at 3 trillion RMB.

Several methods and materials have been developed to prevent corrosion. Corrosion protection coatings account for approximately two‐thirds of all anticorrosion measures. A dense covering layer effectively isolates the metal substrate from corrosive media, thus preventing or slowing down electrochemical reactions on the substrate. However, the coating can become damaged or cracked in harsh environments during transportation and service. Unless it is effectively repaired, such damage will seriously weaken adhesion between the coating and metal substrate, and the barrier properties of the coating will also decline to some degree. A new research focus is smart coatings, defined as coatings that change their properties in response to environmental stimuli. Smart coatings can detect corrosion on metal surfaces at the earliest stage and enable preventive measures. The development of smart coatings for intelligent corrosion control has been expanding in recent years, with continuous application of new knowledge gained from different fields.

This book introduces the latest research on smart coatings for corrosion protection, including self‐healing coatings, self‐reporting coatings, superhydrophobic coatings, weathering‐resistant coatings, and corrosion monitoring techniques based on big data. The book reviews the major processes and strategies for preventing corrosion; techniques for the synthesis and application of smart coatings and multifunctional coatings; and current and future trends in coatings for marine corrosion protection, nuclear corrosion protection, oil/gas corrosion protection, and related fields.

The chapters of this book are organized to provide a comprehensive review of the fabrication, properties, mechanism, and applications of different types of smart coatings. Chapter 1 explores the fundamentals of smart coatings and their corrosion protection capabilities. After a brief introduction to corrosion protection coatings and smart design approaches for intelligent corrosion control, the processes of coating degradation and metal corrosion are discussed in detail so that nonexperts can gain a basic understanding of the corrosion protection techniques. The concepts of self‐healing coatings, self‐reporting coatings, and superhydrophobic coatings are also explained, and the application fields of smart coatings are surveyed. Chapters 2–5 introduce different types of self‐healing coatings, including thermally activated, photothermally activated, pH‐ and redox‐activated, and ion exchange‐activated ones. Specifically, Chapter 2 discusses two thermally activated self‐healing coating systems, covering aspects such as coating preparation, filler preparation, surface characterization, macroscopic and microscopic electrochemical properties, and self‐healing performance. In one system, Ce(NO3)3‐ethylene‐vinyl acetate (EVA) microspheres are added to a shape memory epoxy resin to recover both the corrosion protection properties and adhesion strength. In another coating system containing poly (ε‐caprolactone) microspheres loaded with 8‐Hydroxyquinoline, the good corrosion protection performance is due to the triple actions of (1) the shape memory effect triggered by thermal healing of the coating, (2) the filling effect of molten microspheres, and (3) the action of corrosion inhibitors. Chapter 3 describes the development of a photothermally activated self‐healing coating. Photothermal conversion species such as graphene oxide, titanium nitride, and Fe3O4 are incorporated into micro/nanocontainers and loaded into the coatings. Effects from the type, amount, and dispersion of the photothermal filler on the corrosion resistance, photothermal conversion performance, and self‐healing performance are analyzed. Chapter 4 focuses on two types of pH‐activated and one type of redox‐activated self‐healing coatings. Silica nanoparticles and PDMAEMA macromolecules are pH‐sensitive materials, and redox‐responsive polyaniline can accelerate the release of corrosion inhibitors and the formation of a stable rust layer. Chapter 5 describes the application of layered double hydroxide (LDH) to ion exchange‐activated self‐healing coatings. An LDH nanocontainer containing sustained‐release metavanadate corrosion inhibitors was successfully loaded onto graphene oxide surface, which was added to waterborne epoxy resin to achieve the self‐healing effect.

In Chapters 6–8, pH‐, metal ion‐, and mechanically responsive self‐reporting coatings are introduced. The self‐reporting coatings can autonomously indicate coating damage and metal corrosion in the early stages. They also allow the observation of corrosion initiation over time. Chapter 6 covers several self‐reporting coatings based on different types of corrosion indicators (phenolphthalein, sulfosalicylic acid‐modified carbon dots, and phenanthroline) that either emit fluorescence or display color changes due to pH variation or metallic cations within local defects. The corrosion‐sensing performance and barrier property of these self‐reporting coatings are investigated, and their future development is also discussed. Chapter 7 describes a novel coating with dual self‐reporting and self‐healing functions. 2′,7′‐Dichlorofluorescein (DCF) is loaded into PU/UF microcapsules, which are then dispersed in epoxy to produce a mechanically responsive self‐reporting coating. DCF reacts with the coating matrix containing residual amino groups to produce a prominent red color. For self‐healing performance, the high mobility of the polymer network endows a shape memory effect, allowing the coating to recover its original shape and barrier properties. Chapter 8 presents the design of an active protective epoxy coating with weathering‐resistant, self‐reporting, and self‐healing properties. The mesoporous silica nanocontainers loaded with natural polyphenols (tannic acid and tea polyphenol) can alleviate coating degradation by scavenging radicals generated during UV irradiation. Once the coating is damaged, the polyphenols are released to react with Fe3+ ions, forming a black‐colored chelate that indicates the onset of corrosion. This chelate also inhibits corrosion propagation and therefore offers significant self‐healing effect. Chapter 9 discusses different types of superhydrophobic coatings with improved anti‐icing, anticorrosion, mechanical stabilization, and self‐healing properties. The superhydrophobic property of the coating is achieved by adding CNT–SiO2 hybrids into the coating, and the self‐healing property is achieved by adjusting the proportion of the epoxy resin and curing agent with a flexible chain segment. The damaged coating can heal under thermal or electrical heating by activating the shape memory effect. The stable three‐dimensional network structure and high proportion of flexible chain segments endow the coating with high mechanical durability. Chapter 10 applies atmospheric corrosion monitor (ACM) technique to investigate the self‐healing performance of coatings under three corrosion conditions: room temperature immersion, alternating wet–dry, and outdoor atmospheric exposure. The coating containing zinc phosphate exhibited lower ACM corrosion current values and corrosion charge values compared with the black epoxy coating in all three corrosion conditions, indicating better corrosion resistance, and self‐healing properties. By using the ACM technique, a new approach was developed to assess the failure behavior of coatings in practical application environment. Finally, Chapter 11 overviews future developments of self‐healing, self‐reporting, superhydrophobic, and other novel coatings as well as their various industrial application scenarios. The application of atmospheric corrosion‐monitoring technology to smart coating design is discussed in detail.

This book is largely driven by the requirements of practical applications; therefore, engineers and researchers can choose the type of smart coating most suitable for their application scenarios. This book discusses new synthesis methods to improve the self‐healing efficiency and extend the service life of coatings, new ideas such as combining self‐healing and self‐reporting properties, and new techniques to study localized microscale electrochemical corrosion behavior.

By presenting the latest research progresses in smart protection coatings for intelligent corrosion control, the book should be useful to scientists, researchers, and students from diverse backgrounds. Beyond smart coatings and corrosion protection, it is also relevant to other fields such as materials science, chemical/industrial/manufacturing engineering, and nanotechnology. The book strongly emphasizes the characterization techniques, particularly new techniques for coatings. Note that some of the explanations and expressions are based on the authors' own views and expertise in the field. Readers are also encouraged to take a detailed look at the cited references to further understand the subjects covered in the book.

The authors are grateful to many individuals who contributed to the manuscript, artwork, and typesetting. The authors thank the editorial crew of Wiley Press for accepting the proposal and providing the opportunity to write this book. They are also grateful for the technical support from National Materials Corrosion and Protection Data Center, Liaoning Academy of Materials, and Prof. Xiaogang Li. The authors also thank Dr. Hongchang Qian, Dr. Yao Huang, Dr. Jinke Wang, Dr. Chenhao Ren, Dr. Fan Zhang, Dr. Tong Liu, Dr. Shanghao Wu, Dr. Panjun Wang, Dr. Yue Wang, Dr. Xin Guo, Dr. Zhibin Chen, Dr. Di Xu, Dr. Leping Deng, Yajie Wang, Hao Yang, Xin Wang, Xuanbo Wang, Bing Zhao, Miao Zhao, Xiaolun Ding, Zongbao Li, Weiting Chen, Zhuoyao Chen, Dongfang Jia, and Xueqing Yang for providing assistance with the project. Although the cover lists two authors, this book is really a product of cumulative efforts from numerous scientists and engineers across generations.

February, 2024

Lingwei Ma

Dawei Zhang

Beijing, China

1Fundamentals of Smart Corrosion Protection Coatings

1.1 Introduction of Corrosion Protection Coatings

Metal materials are ubiquitous due to their good mechanical and processing properties, which have been widely applied in industrial production and daily life [1, 2]. However, they are vulnerable to corrosion under the influence of chloride ions, water, oxygen, atmospheric pollutants, etc., causing both economic loss and safety issues [3–5]. According to a survey by the Chinese Academy of Engineering in 2017, the annual cost of corrosion in China is more than 2100 billion yuan, accounting for 3.34% of the gross national product [6].

Many methods and materials have been developed to retard corrosion, with organic coating being one of the most widely used [7–9]. The principle of organic coating is to create a dense covering layer that can effectively isolate the metal substrate from corrosive media, preventing or slowing down the electrochemical reactions on the underlying metal substrate [10, 11]. Corrosion protection coatings account for approximately two‐thirds of all anticorrosion measures. However, these coatings can become damaged or cracked by the harsh environment during transportation and service. Unless effectively repaired in time, such damage will seriously weaken the adhesion between the coating and the metal substrate, and the barrier properties of the coating will also decline to some degree.

Organic coating primers provide corrosion protection in multilayer systems because they have high adhesion strength with the metal substrate, good barrier properties, and can be loaded with large amounts of pigments and fillers. Chromate is often used as an anti‐rust pigment in the organic primer layer due to its excellent corrosion inhibition properties. In recent years, more nontoxic and harmless new corrosion inhibitors have been developed to improve the corrosion resistance of coatings. The limited solubility of the corrosion inhibitor in the coating substrate causes the corrosion inhibitor to be exhausted in a certain period, thus reducing the corrosion protection effectiveness. The disadvantages of directly adding the inhibitor as a pigment can now be overcome by using microcapsules or nanocontainers that store both organic and inorganic inhibitors without any negative impact on the organic material matrix. The top paint should not only have good weather resistance and aging resistance but also must have the necessary decorative effects. It can provide a protective layer for the primer layer. Therefore, the top paint used outdoors must be selected with excellent weather resistance, such as alkyd, polyester, fluorocarbon, polysiloxane, polyacrylate, and polyurethane polymers.

1.1.1 Mechanisms of Corrosion Protection Coatings

The corrosion of metal materials involves three basic processes that occur in parallel: metal dissolution, the reduction of the cathode depolarizing agent, and the conduction of electronic and ionic currents in the cathode and anode [12]. As long as one of the processes is blocked, the metal corrosion rate decreases and the corrosion is suppressed. The protection mechanism of organic coatings is achieved by inhibiting one or more of the abovementioned steps. Some generally recognized anticorrosion mechanisms of coatings are listed below [13]:

(1) Shielding effect: The corrosion reaction of metals requires the presence of water, oxygen, and ions. When these corrosive media penetrate the coating to the coating–metal interface and accumulate at a certain concentration, metal corrosion occurs. The significance of the existence of organic coatings is to effectively prevent or slow down the direct contact between water, oxygen, and the metal matrix, thereby preventing or slowing down the occurrence of corrosion, which requires the coating to have good water resistance, oxygen permeability resistance, and wet adhesion

[14]

. When there is less water and oxygen on the substrate surface, the anode and cathode reactions of corrosion are slow, and the corrosion current is reduced. At the same time, flake pigments, such as mica powder and peeling scales, can be added to the coating. These flake pigments can cut off the pinhole channels in the coating and shield the diffusion of water, oxygen, and ions to the metal substrate

[15]

. Coatings can effectively block the mutual diffusion of corrosive ions, effectively preventing the generation of corrosion products by their moist‐resistant adhesion.

(2) Cathodic protection: When added to the coating, a large amount of metal powder can function as a sacrificial anode in the corrosion process, while the metal substrate acts as the cathode. The metal powder contained within the coating corrodes as a sacrificial anode in the corrosion process of the organic coating/metal system, thus delaying the initiation and development of matrix metal corrosion and effectively protecting the cathode metal [

16

,

17

]. For example, Zn powder can be used for this purpose because Zn has a more negative electrode potential than common metals, such as iron, steel, and aluminum alloys. Moreover, the corrosion products of Zn (the basic zinc chloride and zinc carbonate) can fill pores in the coating, tighten the coating layer, and further reduce the corrosion rate.

(3) Coating adhesion: Coating adhesion is an important characteristic that affects the performance of the corrosion resistance

[18]

. When the adhesion becomes weaker at the coating–metal interface, more corrosive media can leak into the area, and the coating may even fall off. Therefore, stronger coating adhesion (especially after encountering water) can significantly enhance the corrosion resistance of metals.

1.1.2 Failure Type and Failure Mechanism of Corrosion Protection Coatings

Serious coating defects, such as peeling, cracks, loss of mechanical strength, and foaming, occur between the coating and metal interface, which not only affect the aesthetics but also compromise the protection [19]. Figure 1.1 shows the microstructure of corrosion products formed at defects in organic coatings in different systems. The four samples were corroded to different degrees owing to surface defects.

The failure of the organic coating itself does not involve electrochemical corrosion or produce electrical current; rather, it occurs through aging caused by physical and chemical changes. To fundamentally strengthen the protective performance of organic coatings, accurately predict the coating life, and reduce the occurrence of accidents, it is important to find out the failure mechanism of the coating. The microscopic failure mechanism of organic coatings can be divided into four categories:

(1) Aging: Physical aging refers to the deterioration of a coating's protective properties. Swelling, infiltration of corrosive media, and cracking may occur under the action of environmental media and external stress during the coating's service

[20]

. In chemical aging, macromolecules in the chain or network structure are gradually degraded into smaller units, cross‐linked, or undergo other chemical reactions under the actions of light, heat, acid, alkali, and oxygen during the coating's service. Aging facilitates the penetration of external corrosive media and degrades the chemical and physical properties of the coating.

Figure 1.1 Microstructure of corrosion products on defects in organic coatings of different systems.

(2) Hydrolysis: When exposed to external corrosive media, organic coatings expand, causing bubbles or layer damage due to decomposition reactions. Hydrolysis is a typical decomposition reaction [

21

,

22

]. The water resistance of organic coatings depends strongly on their molecular structures.

(3) Photo‐oxygen degradation: The organic coating in outdoor service is subjected to the double action of sunlight and oxygen, and the organic coating will undergo photo‐oxygen aging. Photons with enough energy from light will trigger a light reaction, causing polymer excitation or bond breakage, and the second energy of the light wave will be absorbed.

(4) Thermal failure: When the coating is exposed to high temperatures for a long time, decomposition, aging, and weight loss can easily occur

[23]