The fabrication and characteristics of hydroxyapatite film grown on titanium alloy Ti-6Al-4V by anodic treatment

To improve the growth of hydroxyapatite (HA) coating on the Ti-6Al-4V substrate, a solution containing calcium acetate (CA), calcium glycerophosphate hydrate (Ca-GP), and different concentrations of Na2SO4 as the electrolyte for anodic treatment was investigated in this study. The results found that the anodic method is suitable for Ti-6Al-4V titanium alloy to form an HA coating with the electrolyte consisting of CA, Ca-GP, and Na2SO4. These anodic oxide films display a greater rough structure on the surface of films and the addition of Na2SO4 into the electrolyte during the anodic oxidation process contributes to an increase in the atomic ratio (at%) of Ca in the anodic film. These Ca-containing films are considered bioactive and tend to dissolve into simulated body fluid (SBF) solution and then enhance the degree of the supersaturation of SBF solution with respect to the apatite. Therefore, increasing the concentration of Na2SO4 increases the growth of HA following immersion into SBF. In addition, prior to immersion into SBF solution, the contact angle measurement using an SBF droplet was also investigated for HA growth. The results indicate that when the contact angle of anodic surface is larger, the formation time of HA coating is shorter and it will easily grow a thicker HA. (C) 2020 Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.orgilicenses/by-nc-nd/4.0/).