ABSTRACT
In spite of the growing interest in the corrosion mechanisms of magnesium (Mg) and its alloys, key aspects have not been sufficiently clarified to date. Considerable recent research has addressed the relationships among the chemical composition, the presence and quantity of precipitates, inclusions or impurities and the microstructure of magnesium alloys and their corrosion resistance. However, the precise nature and properties of the thin, air-formed oxide film, which is approximately 3 nm thick, that spontaneously grows on the outermost surface in contact with the atmosphere and its effect on the corrosion of commercial magnesium alloys is still subject to debate. Differences in the thickness, uniformity and chemical composition of these films associated with the alloying element content or the surface conditions of the bulk material may provide basic corrosion-related information that is expected to increase the protective properties for Mg alloys. This entry provides an overview of our current understanding of air-formed oxide films on the surface of magnesium alloys and the possible relationship between the surface composition and degradation of the material. The protective capacity of certain of these thin surface films in different corrosive environments is critically discussed.
