The oxidation of metals

A detailed review of the principles governing the oxidation of metals is presented. The initial stage of the oxidation process involves the chemisorption of oxygen, frequently followed by dissociation and at least partial ionization. Ordered surface adsorption structures occur on many metals, although amorphous structures are found on some metals. Intermediate sub-oxides or 'pseudo-oxides' form prior to the formation of a stable oxide. Considerable oxygen solution occurs in some metals with the formation of internal superlattice domains and sub-oxide platelet structures. Oxide nuclei form at the surface of most metals, the density of nuclei depending on the oxidation temperature and oxygen pressure, and nucleation theory is important for understanding this behavior. The growth of continuous oxide films or scales is considered in terms of various rate limiting processes. A large number of rate laws including linear, parabolic, cubic and quartic as well as logarithmic relations have been derivied. Most of the rate laws derived seem to be satisfactory only over a very limited oxide thickness range.