Effects of temperature and voltage on formation of electrolysis induced chemical conversion coating on titanium surface

Abstract Zinc phosphate chemical conversion technology (PCC) has attracted more attention as a potential surface modification method of biomedical metal. However, it is difficult to prepare a phosphate coating on titanium (Ti) by the traditional PCC methods due to the presence of the passive oxide layer on its surface. In this research, a practical phosphate chemical conversed coating was prepared on Ti by means of electrolysis induced phosphate chemical conversion (EPCC) method. The effects of temperature as well as voltage on the formation, microstructures, properties and the deposition mechanism of coatings are investigated. The results show that the temperature and voltage play important roles in determining the phase composition and crystal structure of the coatings. The coatings obtained by EPCC treatments at 30 °C mainly consist of Zn while that of 90 °C are mainly composed of hopeite grown preferentially along (020) and (040) planes. The results also show that the mechanism of formation of different coatings can be attributed to the influence of process parameters on hydrogen overpotential. Besides, the corrosion resistance of the EPCC coatings is improved by increasing temperature and decreasing voltage.