Effect of processing time on microstructure of surface and corrosion resistance of coatings resulting from plasma electrolytic oxidation on titanium alloy in hydroxyapatite nano-particles electrolyte

In this study, the effect of coating processing time on microstructure of surface and corrosion resistance of coatings resulted by plasma electrolytic oxidation (PEO) was investigated on substrate of TiAl6V4 alloy. The coating processes in hydroxyapatite nano-powder electrolytic were carried out in same conditions of constant voltage of 600V and three different times of 125, 250 and 350 seconds. Studying the microstructure of coatings identified that the coating formed in 125 (s) had more compact and steady structure with fine surface cavities and less porosity. X-ray diffraction pattern of coating demonstrates that this coating is consists of oxide phases of titanium (rutile and anatase) and hydroxyapatite. Also, the study of corrosion resistance of coatings by Potentiodynamic polarization and electrochemical impedance spectroscopy in corrosive solution of chloride sodium 3.5% showed that the coating formed in 125 s has the most noble corrosion resitance potential and the least ICorr and finally the highest resistance to corrosion.