Controlled Potential Electrodeposition of Calcium Phosphate on Ti6Al4V

Abstract

Calcium phosphate (CP) coatings on Ti6Al4V alloy substrates were grown at controlled potential (from ) during electrochemical deposition (ECD) for different times (20 and ). The thickness, structure, and chemical composition of the coatings were investigated by X-ray diffraction, infrared spectroscopy, and scanning electron microscopy. The results showed that the thickness (ranging from ) varies linearly with the square root of deposition time. The hexagonal hydroxyapatite (HA) structure was the main phase at potential of ECD for a period of . The current density–time curves showed that the CP deposition progresses due to initial reduction of the alloy surface oxide layer, after which reduction of nitrate ions and water takes place on the active free surface sites. An increase of pH produced near the electrode surface gives rise to CP precipitation at the electrode surface. The kinetics of this process is enhanced by sufficiently negative potentials. Such potentials determine the structure and composition of ECD products. The coating morphology exhibits an interlocking network of thin, nonoriented, blade-like crystallites and some cloud-like patches, which should provide a relatively large surface area.