In-situ preparation of scholzite conversion coatings on titanium and Ti-6Al-4V for biomedical applications.

A scholzite (CaZn2(PO4)2·2H2O) coating was prepared in situ on commercially pure titanium (cpTi) and Ti-6Al-4V (Ti64) substrates using the chemical conversion technology, and its phase composition and microstructure, as well as mechanical, chemical and biological properties were investigated to explore potential applications as a bioactive coating on bone implants. It is indicated that the coating consists mainly of monoclinic scholzite crystals with nano-thick laminar morphology. The crystals on cpTi aggregate to flower-like particles with the diameter of 5-10μm, while form a network structure homogeneously on Ti64. The scratch test shows that the interfacial bonding strength between the coatings and substrates is higher than 40N. Electrochemical measurements indicate that the corrosion behavior of the coatings is not inferior compared with that of oxide film on substrates. MG63 osteoblast-like cells show good adherence and significantly proliferation and differentiation characteristics on the scholzite coated cpTi and Ti64 (p<0.05) in in-vitro cell tests, demonstrating the cytocompatibility of Ti is significantly improved by the scholzite coating. It is suggested that the scholzite coating might be a promising option in hard tissue replacements for early osteogenesis.