The Effect of Metallographic Preparation on the Surface Characteristics and Corrosion Behaviour of Ti-6Al-4V Alloy in Simulated Physiological Solutions

Abstract

This study aimed to determine the effect of surface metallographic preparation (grinding, diamond polishing, and chemo-mechanical polishing using silica and hydrogen peroxide) on the surface roughness, morphology, chemical composition, and electrochemical behaviour of Ti-6Al-4V alloy. Roughness decreases from ca. 0.2 μm to 0.02 μm from grinding to polishing. A typical α + β microstructure can be observed only after chemo-mechanical polishing. The average composition of ca. 6 wt% Al, 4 wt% V, and rest Ti was determined regardless of the surface preparation. X-ray photoelectron spectroscopy revealed that the thickness of the oxide layer formed on chemo-mechanical polished samples is half that of ground samples. The metallographic preparation largely affects the corrosion behaviour of Ti-6Al-4V, which was investigated using electrochemical impedance spectroscopy and potentiodynamic polarisation in 0.9 wt% NaCl and artificial saliva at 37°C. At the open circuit potential, the chemo-mechanically polished Ti-6Al-4 samples showed superior corrosion resistance over ground samples. At potentials over 2.5 V vs Ag/AgCl, increased current densities were noted for chemo-mechanically polished samples, presumably related to the oxidation to a thicker oxide.