Surface Activation of Ni-Ti Alloy Using Electrochemical Process for Biomimetic Deposition of Hydroxyapatite Coating

Electrochemical depositions of calcium phosphide layer on Ni-Ti alloy in concentrated simulated body flood (SBF×5) were carried out by cathodic electrodeposition. This layer was deposited on Ni-Ti alloy substrate under 10mA/cm2 current density for 2 hours at room temperature. Then, in order to investigate the bioactivity of the pre-calcified samples, they were put in SBF for 1 and 3 days at room temperature. The microstructure, chemical composition, and bioactivity of the coatings were evaluated using scanning electron microscopy(SEM), energy dispersive spectroscopy(EDS), X-ray diffraction(XRD) and Fourier transform infrared spectroscopy(FTIR) techniques. Results showed that the activation of the surface of the Ni-Ti alloy by electrochemical process can significantly enhance the biomimetic deposition during time. On the other hand, by increasing immersion time of pre-calcified samples in SBF from 1 to 3 days, the biomimetic coating uniformly covered the surface of the sample. The ratio of the Ca/P for the pre-calcified sample after immersion in SBF for 3 days was about 1.5 which is very close to the Ca/P ratio of stoichiometric hydroxyapatite.