ELECTROCHEMICAL RESPONSE OF TITANIUM AND CHROMIUM MIXED OXIDES ON TITANIUM SUBSTRATES

The electrochemical response of base titanium electrodes covered with surface films of mixed Ti(IV) and Cr(III) oxides has been studied. The electrodes were prepared from mixtures of their respective hydroxides deposited on Ti substrates, followed by a thermal treatment. An oxidation process at about 1.62 V (vs. SCE) was observed involving the Cr(III) species present in the surface oxide film and giving rise to Cr(VI) species in the solution (electrolyte pH 9.0). The current response and the electro-oxidation efficiency depended on the preparation of the mixed TiO2+Cr2O3 oxides and the amount of Cr(III) deposited. Thermal analysis experiments were performed on pure and/or mixed Ti(IV) and Cr(III) hydroxide samples to interpret more clearly the process occurring when the substrates covered with the hydroxide films are subjected to high temperatures. © 1990.