In order to improve the surface bioactivity of NiTi bone implant and corrosion resistance, hydroxyapatite coating
with addition of 20 wt% silicon, 1 wt% multi walled carbon nano-tubes and both of them were deposited on a NiTi
substrate using a cathodic electrophoretic method. The apatite formation ability was estimated using immersion
test in the simulated body fluid for 10 days. The SEM images of the surface of coatings after immersion in simulated body fluid show that the presence of silicon in the hydroxyapatite coatings accelerates in vitro growth of
apatite layer on the coatings. The Open-circuit potential and electrochemical impedance spectroscopy were measured to evaluate the electrochemical behavior of the coatings in the simulated body fluid at 37 °C. The results
indicate that the compact structure of hydroxyapatite-20 wt% silicon and hydroxyapatite-20 wt% silicon-1 wt%
multi walled carbon nano-tubes coatings could efficiently increase the corrosion resistance of NiTi substrate.