Quantitative Ohmic model for transient growths of passivating films

By employing a Tafel equation for the behavior of the metal/film interface and an Ohmic model for the film itself, it is proposed a qualitatively and quantitatively description for the initial voltammetric transient growths of passivating films on non-noble metals, when they give rise to thin passivating films. General equations are deduced and, as an example of their application, they are used to interpret data obtained during voltammetric growth of ZnO on Zn in a boric/borate buffer solution. The analysis permits the determination of the Flade potential (EF) of the Zn/ZnO/boric–borate system and the exchange current density and transfer coefficient at the Zn/ZnO interface. In relation to the film itself, it is possible to study, during the transient, the dependence of its ionic specific resistivity on the potential, growth rate, and thickness. All these results are interpreted physically.