Solid State Ionics, Vol.78, No.1-2, 69-78, 1995
The Ionic Conductance of Barrier Anodic Oxide-Films on Indium
Formation and growth of thin anodic films on indium in a slightly alkaline berate buffer solution has been studied using galvanostatic and cyclic voltammetry techniques. In the galvanostatic conditions, oxide film growth occurs by activation-controlled ionic conduction by high electric field across the film, according to the exponential law. The following kinetic parameters of film growth have been examined : (i) the electric field strength, which is of the order of 10(6) V cm(-1), (ii) the reciprocal capacity (the unitary formation rate), (iii) the constants A and B of the exponential law, (iv) the height of energy barrier for ion transport in the oxide phase, (v) the effective activation distance for the ionic jump over the energy barrier, and (vi) the pre-polarization oxide thickness. Using cyclic voltammetry, evidence has been given for primary passivation of indium in dynamic conditions. The oxide film formation process is under ohmic resistance control. The change in ohmic resistance is caused by the nucleation and spread of the oxide as a layer on the metal surface.