Current-time dependence in self-organized TiO2 layers synthesis by electrochemical anodization

Titanium based modified surfaces with TiO2 self-organized layers were synthesized by us using electrochemical anodization in phosphate/fluoride electrolyte, at a potential of 20 V, applied with a sweep rate of 0.1 V/s. On Ti6Al4V surfaces manufactured by conventional procedures (turning, milling, polishing) we developed uniform and highly organized nanotubular layers, with nanotubes diameter of 50-100 nm. On surfaces with prior preparation by sand blasting and acid etching (SLA) our oxide layer have a nanoporous structure, with nanopores diameter in 25-65 nm range. The current - time characteristics were recorded by us, and the link between current evolution and the morphology of developing oxide layers was investigated. In the initial potentiodynamic stage of the anodization the current has an initial increase, due to the irregular nanoscale structure initiation, then a drop, caused by regular nanopore/nanotube layer formation. In the potentiostatic stage, after self-organization occurred, by using optimized anodization process parameters the nanotubes growth continues in steady current densities conditions.