Anodization of a Medical-Grade Ti-6Al-7Nb Alloy in a Ca(H ₂PO ₂) ₂-Hydroxyapatite Suspension

Abstract

The electrochemical parameters used for surface treatments should be individually determined for each titanium alloy. In this paper, the parameters for the anodization of a medical-grade Ti-6Al-7Nb alloy in hydroxyapatite suspensions were determined. It was found that formation of a favorable porous oxide layer occurred for the plasma electrolytic oxidation process in a Ca(H ₂PO ₂) ₂ solution with 150 g/dm ³ hydroxyapatite particles at 350 V and 450 V. The differences in the morphology, chemical and phase composition caused variability in the average surface roughness (up 4.25 μm) and contact angle (strongly hydrophilic) values. Incorporation of the hydroxyapatite ceramic particles into formed TiO ₂ layer also influenced the layer thickness and adhesion of the layers to the substrate. The oxide layers formed on the Ti-6Al-7Nb alloy were between 5.19 and 31.4 μm in thickness with an average range of approximately 8–15 μm. The formation of a ceramic layer under controlled electrochemical parameters allows the design of a bioactive surface of implants for bone tissue. The hydroxyapatite particles may promote the osseointegration process. Thus, in this study, the formation of ceramic composites on medical-grade Ti surfaces is presented and discussed.