Polarization Behaviour of Titanium in Sulphuric Acid Solutions

Abstract

When the anodic polarization properties of titanium are investigated in a solution in which the corrosion potential of titanium varies to the positive direction with time, the potential of titanium becomes constant between 1.7 and 1.9 volts (vs.S.C.E.), while the anodic current density is increased and the polarization curve has a plateau. The plateau, which shows the oxygen evolution potential, on the polarization curve can be found neither in the measurement performed in a solution in which the corrosion potential of titanium varies to the negative direction with time, nor in the measurement with the titanium surface which has been pretreated to reduce the natural oxide film 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 the rutile type and non-conductive crystals and the latter is presumably of the rutile type but conductive crystals. An anatase type TiO₂ is formed only when titanium is oxidized in the solution using no current.