Ionic conduction in anodic oxide films on titanium in mixed solutions of aqueous electrolytes and diethylene glycol

Abstract

Steady state kinetic data have been obtained for anodic growth of films on titanium in mixed solution (1:1 by volume) of 100 mol m −3 aqueous orthophosphoric acid with diethylene glycol (DEG), 100 mol m −3 aqueous sodium dihydrogen orthophosphate with DEG and 100 mol m −3 aqueous disodium hydrogen orthophosphate with DEG at different temperatures and current densities. The constant A in the Guntherschulze and Betz equation is temperature dependent while 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 Cabera and Mott. The data have been analysed in terms of Dignam's equation. The effects of current density, temperature and composition of electrolyte on various parameters of Dignam's equation have been examined.