Bioactive surface modification of newly developed β-type titanium alloy for biomedical applications by electrochemical treatment

In order to produce a novel bioactive beta-type titanium alloy -Ti-29Nb-13Ta-4.6Zr - and pure titanium for biomedical applications, an electrochemical treatment involving anodic oxidizing and cathodic polarization was applied to the alloy in calcium nitrate solution under various conditions. For creating a hydroxyapatite (HAP) coating on the alloy, the treated alloy and pure titanium were dipped into simulated body fluid (SBF) and then into 1.5SBF, wherein the concentration of constituents was 1.5 times that of SBF. The characterization and morphology of HAP formed on the alloy were examined in comparison with those of pure titanium. In Ti-29Nb-13Ta-4.6Zr, the formability of HAP in SBF after the electrochemical treatment is less than that in pure titanium. The thickness of a calcium hydroxide layer formed by the cathodic polarization can be controlled by the cathodic potential. In both pure titanium and Ti-29Nb-13Ta-4.6Zr, the formability of HAP increases up to a certain increase in the thickness of the oxide layer formed by the anodic oxidizing. Therefore, the formability of HAP decreases due to a reduction in the formability of the calcium hydroxide layer. The number of hydroxyl groups on the surface of Ti-29Nb-13Ta-4.6Zr is less than that in pure titanium after the anodic oxidizing. The tensile bonding strength of HAP in Ti-29Nb-13Ta-4.6Zr is similar to that in pure titanium.