Formation and characterization of calcium phosphate ceramic coatings on Ti-6Al-4V alloy

Abstract

This present work studies the electrochemical deposition of calcium phosphate ceramic (CPC) coatings on Ti-6Al-4 V alloy substrates. The deposition process was carried out in a phosphate electrolyte containing ammonium dihydrogen phosphate, calcium nitrate tetrahydrate, and hydrogen peroxide, which produces plenty of hydroxyl anions in the electrolyte without the hydrogen bubble liberation. In this experiment, the range of applied deposition voltages was determined based on the result of a cyclic voltammetry measurement. Under different applied voltages, the CPC coatings consisted of a mixed phase of hydroxyapatite, dicalcium phosphate dihydrate, portlandite, and titanium dioxide, which were verified from the results of XRD, XPS and FTIR analysis. Besides, there are two types of surface morphology of the CPC coatings: one is a needle-like structure, and the second is a network-like structure. In addition, the continuous current density (chronoamperometric) and surface morphology at different deposition times were also recorded to predict the growth mechanism of the CPC coatings. The result indicated that the film thickness of the CPC coating was proportional to the total charge and the deposition time. Moreover, the experimental tests were performed through the potentiodynamic polarization and EIS techniques to evaluate the corrosion resistance of the CPC coatings in the simulated body fluid.