Ionic conduction in anodic oxide films on titanium in aqueous electrolytes

Abstract

Steady state kinetic data for anodic growth of films on titanium in aqueous solutions of disodium hydrogen orthophosphate, monosodium dihydrogen orthophosphate and ortho-phosphoric acid at different temperatures have been obtained. The constant (A) of Guntherschulze and Betz equation is temperature-dependent while constant B is temperature-independent. The constant A also depends on the nature of the electrolyte. The data indicate a temperature-independent Tafel slope which rules out the applicability of the single-barrier theory of Cabrera and Mott. The data have been analysed in terms of Dignam's equation. There is an appreciable (2.5%-12.5%) contribution of the quadratic term. The effects of current density, temperature and composition of electrolyte on various parameters of Dignam's equation have been examined