Electrodeposition of cobalt-substituted calcium phosphate coatings on Ti22Nb6Zr alloy for bone implant applications

This work investigates the electrodeposition of cobalt-substituted calcium phosphate coatings on Ti22Nb6Zr alloy designed for bone implant applications. Several electrolytic solutions are tested with various amounts of cobalt. The impact of the addition of hydrogen peroxide (H2O2) to the electrolyte is also explored. The scanning electron microscope observations highlight the specific morphology of the coatings electrodeposited from the solutions with cobalt ions and H2O2. The X-ray diffraction analyses reveal that the substituted calcium phosphate coatings are made of an apatite phase of low crystallinity. The corrosion behaviour of the coated alloys is studied from polarization curves in Hank's solution at 37 degrees C, a physiological solution that simulates the body fluids. The cobalt-substituted calcium phosphate coatings protect the surface of the titanium alloy against the corrosion reactions induced by the aggressive physiological environment. The specific effect of the cobalt substitution is discussed and the corrosion results are compared to those obtained from unsubstituted coatings synthesized in the same experimental conditions. At last, the biocompatibility of this new implant surface is assessed in vitro by determining the cells survival after 24 h, 48 h and 72 h in contact with the electrodeposited coating. (C) 2019 Elsevier B.V. All rights reserved.