Chapter 9 - Oxidation, corrosion and surface treatment

Abstract

This chapter focuses on the oxidation, corrosion, and surface treatment of metals. Metal surfaces commonly oxidize in air at ambient temperatures to form a very thin oxide film (tarnish). This “dry” corrosion is limited, destroys little of the metallic substrate, and is normally not a serious problem. However, at elevated temperatures, nearly all metals and alloys react with their environment at an appreciable rate to form a thick, nonprotective oxide layer (scale). Molten phases may form in the scale layer, which are dangerous because they allow rapid two-way diffusion of reacting species between the gas phase and the metallic substrate. “Wet” or aqueous corrosion, in which an electrochemical attack proceeds in the presence of water, can also destroy metallic surfaces and is responsible for a wide range of difficulties in the industry. The chapter discusses the engineering importance of surfaces and thermodynamics of oxidation. It explains the kinetics of oxidation and several parameters affecting oxidation rates. The chapter concludes with a discussion of oxidation resistance and the electrochemistry of corrosion.