The Effect of pH on the Corrosion Rate of 316L Stainless Steel, Nitinol, and Titanium-6%Aluminium-4%Vanadium in Hank’s Solution

Nowadays, the application of 316L Stainless Steel, Nitinol and Ti-6Al-4V alloys as biomaterials have become popular due to their implant performance and durability. In this research work, the effect of pH on the corrosion rate of 316L Stainless Steel, Nitinol and Ti-6Al-4V alloys have been investigated. An electrochemical method was applied in order to investigate the corrosion behaviour of these biomaterials under simulated biological condition. The potentiodynamic polarization were performed in a Hank’s solution at pH value 7.4 (neutral) and 5.2 (acidic). SEM, XRD, microhardness and surface roughness were also carried out to characterise the corroded surface. The potentiodynamic polarization results showed that both Ti-6Al-4V and 316L stainless steel had high corrosion rate at pH 5.2 (acidic) as compared to pH 7.4 (neutral). The corrosion rate for Ti-6Al-4V alloys at pH 7.4 was 22.80×10-3 mmpy before it increased to 23.65×10-3 mmpy at pH 5.2. Similar behaviour was observed for 316L stainless steel where at pH 7.4 and increase the corrosion rate increasing from 2.387×10-3 mmpy at pH 7.4 to 5.325×10-3 mmpy at pH 5.2. However different corrosion behaviour was observed for Nitinol as the corrosion rate decreasing from 17.65×10-3 mmpy to 16.04×10-3 mmpy at pH 7.4 and 5.2, respectively. Hence, the decrease of pH value was found to not cause any significant effect on the corrosion resistance of Nitinol as compared to 316L SS and Ti-6Al-4V alloys.