The Electrochemical Properties of Titanium (2nd Report)

When the anodic polarization curves of titanium are measured in a solution wherein the corrosion potential of titanium varies to positive direction with time, the potential of titanium becomes constant between 1.7 to 1.9 volt (vs. S. C. E.) while the anodic current density is increased and the curve has an arrest. The arrest, which corresponds to the oxygen evolution potential, on the polarization curve can be found in neither measurement, the one performed in a solution in which the corrosion potential of titanium varies to negative direction with time and the other carried out with the titanium surfae pretreated so that the natural oxide film is reduced cathodically or chemically. From these experiments and electron diffraction studies, it is concluded that the oxide film of titanium produced by electrochemical oxidation is different from the natural oxide film formed in air, and that the former is of rutile type, non-conductive crystals and the latter is presumably of rutile type, conductive crystals. An anatase type TiO2 is formed only when titanium is oxidized in the solution without applied current.