Novel Double Layer Hydroxyapatite (HA)/Ti Coating for Biocompatibility Improvement of Metallic Implants

A novel double layer composite coating composed of a hydroxyapatite (HA) top layer and a single Ti under layer on 316L stainless steel was formed using plasma spraying and physical vapour deposition processes, respectively. Structural characterisation techniques, including XRD, SEM, and EDX, were used to investigate the microstructure, morphology, and crystallinity of the coating. Corrosion behaviour of the coated specimens, as an indication of biocompatability, was also evaluated. Electrochemical potentiodynamic tests were performed in physiological solutions. The results indicate that the double layer HA/Ti coating on 316L stainless steel has a positive effect on the corrosion resistance. The decrease in corrosion current density was significant for these coated specimens and was much lower than the values obtained for uncoated and single HA coated specimens. These results have been compared with the results of the corrosion behaviour of HA coated and uncoated commercially pure Ti and Co-Cr alloys.