STABILITY OF THE ANODIC OXIDE FILM FORMED ON TITANIUM IN DEAERATED NEUTRAL SOLUTIONS

摘要

Properties and stability of the anodic oxide films formed on Ti in various neutral electrolyte solutions were investigated by using impedance measurements. The anodic oxide film was found to be reduced when it was polarized at the potential lower than 0.5 V after the film formation at higher potential. The electric resistivity of the film and the thickness of the space charge layer in the film were gradually decreased accompanying with the reduction. This phenomenon is probably related with the hydration of the film, and the rate of such processes was accelerated by SO_4~(2-) ion in solution. The films formed in the solution containing SO_4~(2-) showed thinner space charge layer, higher donor density, and porous surface. Probably SO_4~(2-) ion is incorporated into the oxide film and induces high concentration of defects affecting the structure of the anodic oxide film.