This chapter discusses the factors influencing the corrosion resistance of bulk materials, namely alloying, metallurgical factors, and mechanical treatments.

This chapter addresses the general effects of composition, mechanical treatment, surface treatment, processing, and fabrication operations on the corrosion resistance of aluminum and its alloys. Different types of surface treatments covered include claddings, anodizing, and conversion coatings. The processing steps that can have relatively significant impact on corrosion resistance are homogenization, rolling, extrusion, quenching, aging, and annealing.

This chapter discusses the effects of metallurgical factors on the corrosion resistance of magnesium alloys. The factors are chemical composition, heat treating, grain size, and cold-work effects. The chapter describes the causes of corrosion failures in magnesium alloys, namely heavy-metal contamination, blast residues, flux inclusions, and galvanic attack.

Stainless steels and nickel-base alloys are recognized for their resistance to general corrosion and other categories of corrosion. This chapter examines the effects of specific alloying elements, metallurgical structure, and mechanical conditioning on the corrosion resistance of these alloys. Some categories of corrosion covered are pitting, crevice, intergranular, stress-corrosion cracking, general, and high-temperature corrosion.

Titanium and its alloys are used chiefly for their high strength-to-weight ratio, but they also have excellent corrosion resistance, better even than stainless steels. Titanium, as the chapter explains, is protected by a tenacious oxide film that forms rapidly on exposed surfaces. The chapter discusses the factors that influence the growth and quality of this naturally passivating film, particularly the role of oxidizing and inhibiting species, temperature, and alloying elements. It also discusses the effect of different corrosion processes and environments as well as hydrogen, stress-corrosion cracking, liquid metal embrittlement, and surface treatments.

This chapter discusses the sintering process for stainless steel powders and its influence on corrosion resistance. It begins with a review of sintering furnaces and atmospheres and the effect of temperature and density on compact properties such as conductivity, ductility, and strength. It then describes the relationship between sintered density and corrosion resistance and how it varies for different types of powders and operating environments. The chapter also explains how stainless steel powders respond to different sintering atmospheres, including hydrogen, hydrogen-nitrogen, and vacuum, and liquid-phase sintering processes.

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 covers the tribological properties of stainless steel and other corrosion-resistant alloys. It describes the metallurgy and microstructure of the basic types of stainless steel and their suitability for friction and wear applications and in environments where they are subjected to liquid, droplet, and solid particle erosion. It also discusses the tribology of nickel- and cobalt-base alloys as well as titanium, zinc, tin, aluminum, magnesium, beryllium, graphite, and different types of wood.

This chapter is dedicated mostly to the metallurgical effects on the corrosion behavior of corrosion-resistant alloys. It begins with a section describing the importance of alloying elements on the corrosion behavior of nickel alloys. The chapter considers the metallurgical effects of alloy composition for heat-resistant alloys, nickel corrosion-resistant alloys, and nickel-base alloys. This chapter also discusses the corrosion implications of changing the alloy microstructure via solid-state transformation, second-phase precipitation, or cold work. It concludes with a comparison of corrosion behavior between cast and wrought product forms.

This chapter is dedicated mostly to the metallurgical effects on the corrosion behavior of corrosion-resistant alloys. It begins with a section describing the importance of alloying elements on the corrosion behavior of nickel alloys. The chapter considers the metallurgical effects of alloy composition for heat-resistant alloys, nickel corrosion-resistant alloys, and nickel-base alloys. This chapter also discusses the corrosion implications of changing the alloy microstructure via solid-state transformation, second-phase precipitation, or cold work. It concludes with a comparison of corrosion behavior between cast and wrought product forms.

This chapter discusses the corrosion behavior of titanium, the types of corrosion that can occur, and the effect of alloying on corrosion resistance. It explains that, due to its tenacious oxide film, titanium has excellent corrosion resistance in oxidizing environments and that the resistance can be extended into the “reducing-acid” region by adding a small amount of palladium. It describes how different grades of titanium respond to different forms of attack, including uniform, crevice, and galvanic corrosion. It also identifies applications where corrosion is often a concern.

This chapter examines the hot corrosion resistance of various nickel- and cobalt-base alloys in gas turbines susceptible to high-temperature (Type I) and low-temperature (Type II) hot corrosion. Type I hot corrosion is typically characterized by a thick, porous layer of oxides with the underlying alloy matrix depleted in chromium, followed (below) by internal chromium-rich sulfides. Type II hot corrosion is characterized by pitting with little or no internal attack underneath. As the chapter explains, chromium additions make alloys more resistant to all types of hot corrosion attacks.

This chapter describes a number of corrosion testing methods for sintered stainless steels, including immersion, salt spray, and electrochemical tests, ferric chloride and ferroxyl tests, and elevated-temperature oxidation resistance tests. It also provides corrosion resistance and performance data from various sources.

Aluminum is protected by a barrier oxide film that, if damaged, reforms immediately in most environments. Despite this inherent corrosion resistance, there are conditions where aluminum alloys, like many materials, are subject to the effects of stress-corrosion cracking (SCC). This chapter describes those conditions, focusing initially on the effects of alloying elements and temper on solution potential and how it compares to other metals. It then addresses the issue of intergranular corrosion and its role in SCC. It explains how factors such as stress loads, grain structure, and environment determine whether or not stress-corrosion cracking develops in a susceptible alloy. It also provides stress-corrosion ratings for many alloys, tempers, and product forms and includes information on hydrogen-induced cracking.

The challenge of materials selection is to achieve adequate performance at the lowest possible cost. Corrosion resistance is not the only property to be considered in making materials selections. Typical requirements and some of the procedures involved in making a selection and some of the factors that must be considered when determining the corrosion performance of a given material are listed in this chapter. The various steps that might be included in a materials selection process are then examined. These include a review of operating conditions and design, the selection of candidate materials, the in-depth evaluation of each candidate material, fabrication requirements, follow-up monitoring, and final materials selection. Material considerations such as cost, materials properties, and processing and fabrication requirements are subsequently covered. Finally, the chapter provides information on materials selection under general corrosion conditions and under conditions of localized corrosion forms such as pitting, crevice corrosion, and stress-corrosion cracking.

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 discusses various factors that affect corrosion of stainless steel weldments. It begins by providing an overview of the metallurgical factors associated with welding. This is followed by a discussion on preferential attack associated with weld metal precipitates in austenitic stainless steels as well as several forms of corrosion associated with welding. The effects of gas-tungsten arc weld shielding gas composition and heat-tint oxides on corrosion resistance are then covered. Microbiological corrosion of butt welds in water tanks is also illustrated. In addition, the chapter provides information on corrosion of ferritic and duplex stainless steel weldments.

This chapter discusses corrosion prevention methods used with aluminum and its alloys. The methods range from relatively straightforward measures, such as proper handling and storage, to advanced early warning corrosion monitoring systems for military aircraft. The chapter summarizes the basic factors that influence design for corrosion resistance and discusses the use of conversion coatings, organic coatings, porcelain enameling, and electroplating. It also discusses corrosion monitoring methods used in chemical processing and refining industries.

This chapter covers the corrosion behavior of beryllium in aqueous environments. It describes the chemical reactions that drive the corrosion process, the conditions required for equilibrium, and the factors that affect corrosion resistance. It discusses the stability of the native oxides that form on the surface of beryllium and their ability to withstand acids, bases, and corrosive agents found in rain and seawater. It explains how carbides, inclusions, ions, and impurities contribute to corrosion damage, particularly pitting, and how corrosion reduces the ductility and fracture strength of certain beryllium alloys.