Surface characterization of implant materials cp Ti, Ti-6Al-7Nb and Ti-6Al-4V with different pretreatments

The biocompatibility of commercially pure titanium and its alloys is closel y related to their surface properties, with both the composition of the pro tecting oxide film and the surface topography playing an important role. Su rfaces of commercially pure titanium and of the two alloys Ti-6Al-7 Nb and Ti-6Al-4V (wt %) have been investigated following three different pretreatm ents: polishing, nitric acid passivation and pickling in nitric acid-hydrog en fluoride. Nitric acid treatment is found to substantially reduce the con centration of surface contaminants present after polishing. The natural 4-6 nm thick oxide layer on commercially pure titanium is composed of titanium oxide in different oxidation states (TiO2, Ti2O3 and TiO), while for the a lloys, aluminium and niobium or vanadium are additionally present in oxidiz ed form (Al2O3, Nb2O5 or V-oxides). The concentrations of the alloying elem ents at the surface are shown to be strongly dependent on the pretreatment process. While pickling increases the surface roughness of both commerciall y pure titanium and the alloys, different mechanisms appear to be involved. In the case of commercially pure titanium, the dissolution rate depends on grain orientation, whereas in the case of the two alloys, selective alpha- phase dissolution and enrichment of the beta-phase appears to occur. (C) 19 99 Kluwer Academic Publishers.