Abstract
It has already been made clear that corrosion resistance of titanium is improved by change of passive film composition from TiO and Ti2O3 to TiO2. Therefore, in this paper, the effect of TiO2 coating on corrosion resistance of titanium was investigated Anodized, thermally oxidized and PdO/TiO2 coated titanium specimens were used. Anodized titanium showed the same corrosion resistance as polished titanium did. This is due to the fact that anodized film was consisted of hydrated TiO2 which dissolved in an HCl solution for short time. Corrosion resistance of titanium was significantly improved by thermally oxidation because of formation of TiO2 which was stable even in a highly acidic solution. PdO/TiO2 coated titanium showed an excellent corrosion resistance in HCl solutions. Moreover, crevive corrosion was suppressed by the coating. Many cracks were observed in PdO/TiO2 films and titanium substrate was exposed at the crack. However, titanium substrate is polarized anodically to passive potential region by PdO/TiO2 film because the coating film has high corrosion potential. This is a reason why PdO/TiO2 coated titanuim shows an excellent corrosion resistance.
