Hydroxyapatite Coatings for NiTi Implants

NiTi shape memory alloy cannot provide all the clinical requirements of an implant due to the high nickel content and bio-inert surface.  Thus, its surface is coated by bio-ceramics such as hydroxyapatite (HA) in different methods in order to improve biocompatibility and bioactivity. In the present study, a bio-active coating of HA using electrophoretic deposition technique was created on the surface of NiTi alloy to act as a barrier and prevent the diffusion of nickel ions in to the body fluid. A suspension was prepared by n-butanol as solvent and triethylenamine as dispersant. Coatings were deposited at different voltage of 40, 60 and 80 V for duration of 120s on the cathode. Then coated samples were sintered at 800 °C under argon atmosphere for 2 hrs. Evaluation of coatings was performed by X-ray diffraction techniques (XRD), scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDX). Bioactivity and corrosion behavior of HA coatings was studied within simulated body fluid (SBF) environment. The results showed, the sample coated at 60 V is dense, uniform, owing proper corrosion resistant, and also the ability for nucleation and growth of apatite layer in SBF.