From Bacon to barriers: a review on the passivity of metals and alloys

Passivity of metals and alloys is a phenomenon of utmost technical importance as it prevents many construction materials from rapid deterioration. For the majority of metals , passivity is based on the spontaneous formation of a thin oxide layer (the passive film), in a specific environment. This film can slow corrosion (dissolution) reactions by many orders of magnitude. The present review tries to give an overview of several important aspects and factors that influence film formation, stability and breakdown. Emphasis is on chemical stability and its connection to thermodynamic, kinetic and electronic aspects of the metal/oxide/environment system. Although some metals (e.g. Fe) and alloys (e.g. Fe/Cr) are treated with greater depth, the focal point is the description or general mechanistic approaches - for specific systems the reader is referred to secondary literature.