Corrosion resistance of Ti-6Al-4V alloy finished by an advanced ELID grinding system

Metallic biomaterials, such as titanium alloys and stainless steels, require enhanced chemical stability, which is dependent on the quality and thickness of the oxide layer on a material surface. Therefore, if we can form a thick and stable oxide layer during machining, it is very effective in improving the surface properties. This will also help us to skip other surface treatment and allow for significant saving in energy and procedure. The author previously proposed a new ELID grinding system, in which a direct current of extremely short pulses are applied to the workpiece being ground. In this study, to ensure the fabrication of a surface with desirable characteristics for biomaterials, three types of specimens, which were processed with different surface finishing methods were prepared. The processed surfaces were analyzed by performing ultimate analysis using an Energy Dispersive X-ray analyzer (EDX). To measure the thickness of surface oxide layers, detailed observations were performed by using an X-ray Photoelectron Spectroscopy (XPS). In order to investigate corrosion resistance, electrochemical corrosion tests were carried out using a three electrode electrochemical cell connected to a computer driven potentiostat. EDX and XPS analysis indicated a significantly thicker oxide layer for surfaces modified by the proposed technique. The results of corrosion resistance testing suggest that surfaces finished using this technique inhibit a pitting of the surface and prevents dissolution of metal-ions because of the thick oxide layer. Consequently, the proposed technique improves chemical properties compared to those of polished and conventional ELID ground surface.