Evaluation of corrosion and tribocorrosion of plasma electrolytic oxidation treated Ti-6Al-4V alloy

In this study the corrosion and tribocorrosion of oxide films on Ti-6Al-4V alloy, prepared by an anodic oxidation treatment in H2SO4/H3PO4 electrolyte at potentials higher than the spark voltage, were evaluated. Polarization curves showed a significant increase in corrosion resistance after spark oxidation. Moreover, the results exhibited more positive corrosion potential and higher corrosion current density at higher anodising voltages. Tribocorrosion results indicated that for samples anodised at lower voltages, the open circuit potential drops sharply down to negative values. But samples anodised at higher voltages showed lower potential drop with slower slop. SEM and EDS of worn surfaces indicated that the oxide layer on samples anodised at lower voltages is totally removed, but for samples anodised at higher voltages, the oxide layer is only locally removed within the wear track. Moreover, measurement of wear volume of treated samples exhibited lower values on samples anodised at higher voltages.