Corrosion is a key subject for more or less all classes of alloys that fall within the broad definition of stainless steels because these alloys were developed with the intention of preventing corrosion. This chapter provides an introduction to the fundamentals of electrochemical theory as it pertains to corrosion resistance of stainless steels. The discussion provides an overview of electrochemical reactions, Faraday's law, the Nernst equation, galvanic versus electrochemical cells, corrosion tendency, and Pourbaix diagrams.

This chapter concentrates on the better-known and widely studied phenomenon of pitting corrosion of passive metals. The discussion focuses on different parameters that influence pitting corrosion, namely environment, metal composition, potential, temperature, surface condition, and inhibitors. It also provides information on various stages of pitting: passive film breakdown, metastable pitting, pit growth, and pit stifling or death.

High-strength steels are susceptible to stress-corrosion cracking (SCC) even in moist air. This chapter identifies such steels and the applications where they are typically found. It provides information on crack growth kinetics and crack propagation models in which hydrogen embrittlement is the predominant mechanism. It explains how different application variables affect SCC, including loading mode, state of stress, type of steel, temperature, electrochemical potential, heat treatment, and deformation processes. It also compares SCC characteristics in different high-strength steels and discusses the influence of composition, steelmaking practice, and application environment.

Stress-corrosion cracking (SCC) in magnesium alloys was first reported in the 1930s and, within ten years, became the focus of intense study. This chapter provides a summary of all known work published since then on the nature of SCC in magnesium alloys and how it is related to composition, microstructure, and heat treatment. It describes the types of environments where magnesium alloys are most susceptible to SCC and the effect of contributing factors such as temperature, strain rate, and applied and residual stresses. The chapter also discusses crack morphology and what it reveals, provides information on proposed cracking mechanisms, and presents a practical approach for preventing SCC.

This chapter takes a practical approach to the problem of stress-corrosion cracking (SCC) in stainless steels, explaining how different application environments affect different grades of stainless steel. It describes the causes of stress-corrosion cracking in chloride, caustic, polythionic acid, and high-temperature environments and the correlating effects on austenitic, ferritic, duplex, martensitic, and precipitation hardening stainless steels and nickel-base alloys. It also discusses the contributing effects of sensitization and hydrogen embrittlement and the role of composition, microstructure, and thermal history. Sensitization is particularly detrimental to austenitic stainless steels, and in many cases, eliminating it will eliminate the susceptibility to SCC. The chapter includes an extensive amount of data and illustrations.

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 complex polarization characteristics of active-passive metals and addresses related problems in interpreting their corrosion behavior. It begins by presenting several experimentally derived polarization curves for iron, comparing and contrasting them with the iron-water Pourbaix diagram. It then explains how anodic polarization is extremely sensitive to the environment and, as a result, a reasonably complete curve for a given metal-environment system usually can only be inferred. It goes on to describe how such curves are constructed, demonstrating the procedures for a wide range of alloys and environments. The examples also show how factors such as alloy concentration, crystal lattice orientation, temperature, and dissolved oxygen affect corrosion behavior.

This chapter addresses the issue of stress-corrosion cracking (SCC) in carbon and low-alloy steels. It discusses crack initiation, propagation, and fracture in aqueous chloride, hydrogen sulfide, sulfuric acid, hydroxide, ammonia, nitrate, ethanol, methanol, and hydrogen gas environments. It explains how composition and microstructure influence SCC, as do mechanical properties such as strength and fracture toughness and processes such as welding and cold work. It also discusses the role of materials selection and best practices for welding.

This chapter outlines the major types of corrosion, their interactions, their complicating effects on fracture and wear, and some possible prevention methods. The types of corrosion considered in the chapter are galvanic corrosion, uniform corrosion, pitting corrosion, crevice corrosion, microbiologically influenced corrosion, stress-corrosion cracking, and corrosion fatigue.

This chapter focuses on stress-corrosion cracking (SCC) of metals and their alloys. It is intended to familiarize the reader with the phenomenological and mechanistic aspects of stress corrosion. The phenomenological description of crack initiation and propagation describes well-established experimental evidence and observations of stress corrosion, while the discussions on mechanisms describe the physical process involved in crack initiation and propagation. Several parameters that are known to influence the rate of crack growth in aqueous solutions are presented, along with important fracture features.

This chapter outlines the step-by-step processes by which materials are selected in order to prevent or control corrosion and includes information on materials that are resistant to the various forms of corrosion. The various forms of corrosion covered are general (uniform) corrosion, localized corrosion, galvanic corrosion, intergranular corrosion, stress-corrosion cracking, hydrogen damage, and erosion-corrosion. In addition, the economic importance of cost-effective materials selection is also considered.

This chapter is a detailed study of the localized corrosion behavior of steel, copper, and aluminum alloys. It applies the basic principles of electrochemistry, as well as materials science and solid and fluid mechanics, to explain the causes and effects of pitting, crevice corrosion, stress corrosion cracking, and corrosion fatigue. It describes the underlying mechanisms associated with each process and how they relate to the microstructure of the metal or alloy, the physical condition of the surface, and other factors such as the coupling of the metal to a dissimilar metal or surface film.

This chapter discusses the conditions and sequence of events that lead to stress-corrosion cracking (SCC) and the mechanisms by which it progresses. It explains that the stresses involved in SCC are relatively small and, in most cases, work in combination with the development of a surface film. It describes bulk and surface reactions that contribute to SCC, including dissolution, mass transport, absorption, diffusion, and embrittlement, and their role in crack nucleation and growth. It also discusses crack tip chemistry, grain-boundary interactions, and the effect of stress-intensity on crack propagation rates, and describes several mechanical fracture models, including corrosion tunnel, film-induced cleavage, and tarnish rupture models.

This chapter describes nondestructive evaluation (NDE) test methods and their relative effectiveness for diagnosing the cause of stress-corrosion cracking (SCC) service failures. It discusses procedures for analyzing various types of damage in carbon and low-alloy steels, high-strength low-alloy steels, hardenable stainless steels, austenitic stainless steels, copper-base alloys, titanium and titanium alloys, aluminum and aluminum alloys, and nickel and nickel alloys. It identifies material-environment combinations where SCC is known to occur, provides guidelines on how to characterize cracking and fracture damage, and explains what to look for during macroscopic and microscopic examinations as well as chemical and metallographic analyses. It also includes nearly a dozen case studies investigating SCC failures in various materials.