Characterization of anodic oxide growth on commercially pure titanium in NaTESi electrolyte

The present study examines the formation of anodic oxide films on commercially pure titanium in NaTESi electrolyte at a constant current density of 20 mA cm− 2. The barrier-type titanium oxide films of ~ 30, 37 and 67 nm thick are formed when anodized to 5, 10 and 20 V. However, a porous film of approximately 80.0 nm thick is developed after anodizing to 40 V. Significant sodium species were found throughout the oxides and the concentration increases with the increase of anodic voltage. The growth efficiency is reduced by increasing the anodic voltage, due to formation of crystalline phase in the oxide, which induces oxygen generation. The degree of crystallinity of the anodic oxide film formed on titanium is increased associated with the increase of the anodic voltage. The dielectric permittivity of the anodic oxide film is estimated as 2.35 based on the oxide thickness measured when anodized to 10 V.