ABSTRACT
Metals in service often give a superficial impression of permanence, but all except gold are chemically unstable in air and air-saturated water at ambient temperatures, and most are also unstable in air-free water. From initial encounters with the effects of corrosion processes, it may seem difficult to accept that they can be explained on a rational basis. The chapter discusses thermal oxidation which includes protective oxides and nonprotective oxides. Corrosion processes can interact with a stressed metal to produce fracture at critical stresses of only fractions of its normal fracture stress. Stress-corrosion cracking is restricted to particular metals and alloys exposed to highly specific environmental species. The chapter also discusses strategies for corrosion control that include passivity, conditions in the environment, cathodic protection, protective coatings and corrosion costs. The criterion for corrosion failure is therefore premature termination of the useful function of the metal by interaction with its environment, before the planned life has elapsed.
