In this study the surface characteristic of oxide films on Ti-6Al-4V alloy formed by an anodic oxidation treatment in H 2 SO 4 /H 3 PO 4 electrolyte was evaluated. The oxide film was formed under potentiostatic condition at potentials higher than the breakdown voltages. The effect of anodizing voltage on the corrosion and tribocorrosion behavior of material was also investigated. The corrosion of oxide layers was studied using electrochemical potentiodynamic polarization and electrochemical impedance spectroscopy(EIS) techniques, in 0.9wt% NaCl solution. Polarization curves showed a significant rise in the corrosion resistance after spark oxidation. Moreover the results exhibited more positive corrosion potential and higher corrosion current density at higher anodizing voltage. The obtained EIS spectra and their interpretation in terms of an equivalent circuit with the circuit elements representing the electrochemical properties of two oxide layers (composed of porous outer layer and dense inner layer), space charge region and diffusion, were in a good agreement. Evaluation of tribocorrosion of oxide layers produced at various anodizing voltages was studied in 0.9wt% NaCl measuring the free corrosion potential with respect to Ag/AgCl 2 reference electrode. It was observed that for samples anodized at lower voltages, the open circuit potential drops sharply down to negative values due to the removal of oxide films. But for samples anodized at higher voltages, the results indicated lower potential drop having a slower slop. After being tested, the surface of samples were investigated by SEM and EDS. Results obtained indicated that the oxide layer on samples anodized at lower voltages is totally removed, but for samples anodized at higher voltages the oxide layer is only locally removed within the wear track. Moreover, measurement of wear volume loss exhibited lower wear volume in samples anodized at higher voltages. These results indicated a better tribocorrosion behavior due to increasing the anodizing voltage. Morphology of the surface layers was studied by scanning electron microscope (SEM). The results indicated that the diameter of pores and porosity of oxide layer increase with anodizing voltage. The thickness of the layer was measured on the cross sections of samples by SEM. The results showed a linear increase of thickness with increasing the anodizing voltage. The EDS analysis of oxide films formed in H 2 SO 4 /H 3 PO 4 at potentials higher than breakdown voltage, demonstrated the precipitation of sulfur and phosphor elements from electrolyte into the oxide layer. The roughne measurement of oxide layer showed that in spark anodizing, the Ra and Rz parameters would increase with increasing anodizing voltage. Key Words: anodizing, breakdown voltage, tribocorrosion, EIS.