KINETIC-MODEL OF ANODIC-OXIDATION OF TITANIUM IN SULFURIC-ACID

A kinetic model for the galvanostatic oxidation of titanium is proposed and compared with experimental results. The kinetic model takes account of the oxidation of titanium, the incorporation process, the evolution of oxygen, the avalanche process, the dissolution of titanium oxide and the capacitance effect of the double layer. The results indicate that the dissolution rate of titanium oxide is negligible and that the rate of oxygen evolution plays an important role in the anodic oxidation. The kinetic model is developed further for the following three special cases: Case 1: when the anodization time approaches zero dV/dt = K(I(t) - I0 - I(d)) Case 2: when the anodization time is larger than the transition time (tau) dV/dt = K(I(t) - I(e) - I(O2)* - I(d)) Case 3: when the anodization time is smaller than the transition time (tau) dV/dt = K(I(t) - I(e) - (xit/1 + xit) I(O2)* - I(d)) where K and xi are constants and I(t), I0, I(e), I(O2)* and I(d) are the applied current density, primary electron current density, rate of avalanche process, rate of oxygen evolution and dissolution rate of titanium oxide, respectively. The predictions of the proposed kinetic model correlate well with the experimental results.