Kinetics of Oxide Growth of Passive Films on Transition Metals

Abstract

The objective of this article is to summarize the oxide growth mechanisms and rate controlling processes for typical transition metals such as Fe, Cr, and Ni in aqueous solutions. Kinetic expressions and mechanisms for oxide growth at potentials in the passive range as defined in Section 3.1 are described based on the Mott–Cabrera, Fehlner–Mott, point defect, and the generalized growth models. It is shown that oxide growth can be controlled by either the metal cation ejection rate at the metal/film interface, the transport kinetics of defects as charge carriers across the passive film, or the metal cation dissolution rate at the oxide/solution interface. Thin passive films (x < 10–20nm) may exhibit direct logarithmic, inverse logarithmic, parabolic, or linear growth with respect to time depending on which model is applied while thick films grow by parabolic kinetics.