Surface pre-treatments of Ti-Nb-Zr-Ta beta titanium alloy: The effect of chemical, electrochemical and ion sputter etching on morphology, residual stress, corrosion stability and the MG-63 cell response

Abstract

Pre-treatment methods for titanium alloys are of great importance, both as regards the treatment of the surfaces of the implant and as regards the pre-deposition phase of the coating processes and the surface modifications. We have investigated the impact of chemical, electrochemical and ion sputter etching on the surface properties, the corrosion stability and the MG-63 cell response of Ti-35Nb-7Zr-5Ta alloy. In the initial state, the samples have a mechanically polished surface. The pre-treatments that were applied led to significant morphological changes in microscale and also in nanoscale. The wettability of the pre-treated surfaces varied from hydrophilicity to hydrophobicity. Changes in contact angle were controlled by surface chemistry rather than changes in morphology and roughness. Native oxides and suboxides of alloying elements with a predominant amount of Nb2O5 were found to provide high corrosion stability of Ti-35Nb-7Zr-5Ta alloy after mechanical polishing, after chemical etching and after electrochemical etching. Significantly reduced corrosion resistance in a physiological saline solution was observed for the ion sputtered surface. A decreasing trend in the cell spreading area correlated with increasing surface roughness and decreasing polarization resistance. There is discussion of the causes of the changes in surface properties and cell behaviour.