The basic concept for most methods of corrosion protection is to remove one or more of the electrochemical cell components so that the pure metal or metal alloy of interest will not corrode. Another widely used corrosion protection approach is to change the nature of the anode so that it becomes the cathode (cathodic protection). This chapter briefly reviews these methods of corrosion protection. The factors affecting corrosion behavior are covered. In addition, the chapter provides information on coatings and inhibitors, which are used in corrosion protection.

Superalloys tend to operate in environments where they are subjected to high-temperature corrosion, oxidation, and the erosive effects of hot gases. This chapter discusses the nature of these attacks and the effectiveness of various protection methods. It describes the primary forms of oxidation, the development of protective oxides, and the conditions associated with mixed gas corrosion and hot corrosion attack. It discusses oxidation and corrosion testing, the equipment used, and various ways to present the associated data. It describes the effect of gaseous oxidation on different alloys, discusses the formation of oxide scale in the presence of mixed gases, and explains how alloy composition contributes to oxide growth. The chapter discusses the underlying chemistry of hot corrosion, how to identify its effects, and how it progresses under various conditions. It also discusses protective coatings, including aluminide diffusion, overlay, and thermal barrier types, and how they perform in different environments based on their ability to tolerate strain.

This article describes in detail the process of corrosion control by cathodic and anodic protection. The discussion covers the basic concept of cathodic and anodic protection systems, their types and equipment used, and the advantages, limitations, and applications of these protection systems. The types of cathodic protection systems include sacrificial cathodic protection and impressed-current cathodic protection systems. Some of the technical problems associated with cathodic protection include the effects of stray currents on the corrosion of adjacent metal structures, the effects of the chemical reactions occurring at the surface of the protected structure, and the effects of cathodic protection on coatings.

Organic coatings (paints and plastic or rubber linings), metallic coatings, and nonmetallic inorganic coatings (conversion coatings, cements, ceramics, and glasses) are used in applications requiring corrosion protection. These coatings and linings may protect substrates by three basic mechanisms: barrier protection, chemical inhibition, and galvanic (sacrificial) protection. This chapter begins with a section on organic coating and linings, providing a detailed account of the steps involved in the coating process, namely, design and selection, surface preparation, application, and inspection and quality assurance. The next section discusses the methods by which metals, and in some cases their alloys, can be applied to almost all other metals and alloys: electroplating, electroless plating, hot dipping, thermal spraying, cladding, pack cementation, vapor deposition, ion implantation, and laser processing. The last section focuses on nonmetallic inorganic coatings including ceramic coating materials, conversion coatings, and anodized coatings.

Managing corrosion continues to be a challenge for operators of modern boilers worldwide. This chapter addresses the corrosion-related problems that can occur in boilers burning municipal solid waste (MSW). It describes corrosion mechanisms associated with different environments and alloys. It also discusses corrosion protection methods for furnace waterwalls and superheater tubes in waste-to-energy boilers.

This chapter contains sample problems with worked solutions pertaining to the application of corrosion inhibitors. Correct answers require an understanding of potentiodynamic polarization scan (PDS) curves, the determination of corrosion current and inhibitor efficiency, and the development of a test plan to evaluate the long-term corrosion protection of a potential inhibitor.

Magnesium occupies the highest anodic position on the galvanic series and can be subject to severe corrosion. The corrosion problem is due to the impurity elements iron, nickel, and copper. However, the use of higher-purity magnesium alloys has led to corrosion resistance approaching that of some of the competing aluminum casting alloys. This chapter begins with a general overview of magnesium metallurgy and alloy designations and moves on to discuss in detail the nominal compositions, mechanical properties, heat treatment, fabrication, and corrosion protection of magnesium casting alloys and wrought magnesium alloys. It also discusses the nominal compositions, properties, and applications of commercially pure zinc, zinc casting alloys, and wrought zinc alloys.

Corrosion can be defined as a chemical or electrochemical reaction between a material, usually a metal, and its environment that produces a deterioration of the material and its properties. This chapter describes the effects and economic impact of corrosion in major industrial plants. The emphasis in this chapter, as well as in other chapters in this book, is on aqueous corrosion, or corrosion in environments where water is present. The chapter describes the classification of various forms of corrosion based on the nature of the corrodent, mechanism of corrosion, and appearance of the corroded metal. It discusses five primary methods of corrosion control, namely, material selection, coatings, inhibitors, cathodic protection, and design. Examples of the opportunities in corrosion control and the means to implement a program to capitalize on those opportunities are presented in a table. The chapter concludes with varied sources of information pertaining to corrosion and corrosion prevention.

This chapter discusses the ambient-temperature corrosion characteristics of aluminum metal-matrix composites (MMCs), including composites formed with boron, graphite, silicon carbide, aluminum oxide, and mica. It also discusses the effect of stress-corrosion cracking on graphite-aluminum composites and the use of protective coatings and design criteria for corrosion prevention.

Cold spray coatings technology has the potential to provide surface enhancement for applications in sectors such as defense and aerospace, oil and gas, power generation, medical, automotive, electronics, and railways. The ability to deposit clean metallic coatings is used in applications requiring corrosion/oxidation protection, erosion/wear protection, additive manufacturing, and fabricating free forms. This chapter discusses the function, advantages, and benefits of some of these applications.

Anodic protection is used on a smaller scale than other corrosion control techniques due to the fundamental electrochemistry involved. This chapter provides a brief history of the technique, discusses anodic protection use, and compares anodic and cathodic protection. The background and theory of anodic protection are summarized. In addition to briefly describing the various items used for each component of an anodic protection system, the chapter presents design concerns as well as applications of the system. Factors concerning the economic justification of anodic protection are also described.

This chapter covers the engineering aspects of corrosion inhibitors and their effect on corrosion reactions. It explains how different metallic salts and heterocyclic compounds influence chemical reactions on metal surfaces exposed to corrosive media or environments. It describes how to evaluate inhibition efficiency through weight loss measurements, linear polarization resistance tests, electrochemical impedance spectroscopy, electrochemical noise monitoring, and surface analysis. It demonstrates the use of potentiodynamic polarization curves, Tafel extrapolations, equivalent circuit models, and various methods for characterizing corrosion damage and protective surface films. It also discusses typical applications, industry trends, and the emerging role of high-throughput experimentation, quantitative modeling, and machine learning in the development of cleaner and more effective corrosion inhibitors.

This chapter begins with a brief review of the different types of surface treatments and coatings used in industry and their effect on properties and performance. It then discusses the importance of corrosion and wear treatments and the consequences of failing to properly implement them in critical industries such as mining, energy production, transportation, and mineral and chemical processing. The chapter also describes basic approaches to dealing with corrosion and wear in steel.

This chapter discusses the formation and control of aqueous corrosion in iron and steel. It also provides information on passivation, stress corrosion, rust, and direct oxidation.

This chapter discusses the application of high-pressure cold spray to the automotive industry field, with special attention to three applications: additive manufacturing, fabrication methods, and protective coatings. Various studies on the automotive application of cold spray are reviewed. The background and purpose of each application are presented and practical cases are discussed.

This chapter discusses the effect of composition on environmental resistance, machinability, and casting and forging, factors that are often considered when selecting a superalloy.