The Effect of pH Value on the Corrosion Behaviour of Ti-6Al-4V and 316L SS Alloys under Physiological Environment

Abstract

The corrosion behaviour for stainless steel 316L and Ti-6Al-4V at pH 5.2 and 7.4 under simulated biological conditions either with or without the presence of proteins were investigated using electrochemical methods. The electrochemical tests were performed with and without the addition of bovine serum albumin (BSA) withconcentration of 10 g L-1 to the phosphate buffer solution (PBS) with two different phases of pH, which areacidic (pH 5.2) and neutral phase (pH 7.4) at 37 °C. The electrochemical methods used in this study were open circuit potential (OCP) and potentiodynamics polarization. The results of electrochemical tests showed that the corrosion potential (Ecorr) values of stainless steel at both pH values are slightly higher than Ti-6Al-4V in absence of BSA. The chromium (III) oxide (Cr2O3) film formed on stainless steel is more stable in neutral and also in acidic one without the presence of proteins. Meanwhile, the Ecorr of Ti-6Al-4V increases at acidic (-611.0 mV) and neutral pH (-585.0 mV) of human body in phosphate buffer solution (PBS) with addition of BSA, compared to test medium without the addition of proteins. This shows the interaction between proteins and surface of the Ti-6Al-4V have no significant effect onto its corrosion behaviour. However, the Ecorr of Ti- 6Al-4V at condition acidic pH with the absence of proteins, which is -740.0 mV showed the lowest corrosion resistance than stainless steel (Ecorr = -652.0 mV). In terms of corrosion rate values, stainless steel alloyshowed the best corrosion rate in neutral pH, which is 3.048 × 10-3 without addition of BSA in solution. But both alloys show greater corrosion rate at normal phase condition compared to acidic phase condition.