Influences of pH Value and Deposition Time on HA/TiO2 Coatings Deposited by Electrochemical Method

With titanium alloy after micro-arc oxidation as substrate, HA/TiO2 coatings were prepared by electrochemical method. The coatings were characterized by means of SEM and XRD. Variation of pH value of electrode/electrolyte was measured by means of pH microprobe during treatment, and the influences of pH value and deposition time on HA/coatings by this method were investigated. The results show that micro-arc oxidation treatment are helpful to obtain a good adhesion between HA and substrate, and HA crystals are well-distributed on the TiO2 film surface. The increasing of the pH value of treatment solutions results in higher crystallinity of HA crystals. During the process of deposition, pH value on the surface of the electrode increases at first and then decreases with deposition time, but pH value of electrolyte decreases with the deposition time. pH value has obvious influence on the morphology of HA crystals, and the size of HA crystal increases with the deposition time within certain limits. However, the size of HA crystal is abnormally large if the deposition time is too long.