Dissolution Behaviour of Titanium Oxide in H ₂ SO ₄ and NaOH from Impedance. and Potential Measurements

The open-circuit behaviour of the anodic oxide film on titanium was studied in sulphuric acid and sodium hydroxide solutions by impedance and potential measurements. It was found that the film dissolves in sodium hydroxide and to a lesser extent in sulphuric acid. In both cases the measured capacitance, Cm, increases with time, t, according to Cm−1 = α – βt½ where α and β are coefficients dependent on the test solution. Thefilm was found to be duplex in nature. The outer layer is more defective than the inner one and therefore it is more susceptible to dissolution in both H2SO4 and NaOH.