The electrochemical scratch technique was used to compare the biocompatibility of Nitinol alloy and 316L Stainless Steel in vitro. The purpose of this study was to analyze the corrosion behavior of Nitinol medical devices or implants; specifically, to investigate the repassivation potential. Cylindrical samples of each alloy were tested in a corrosion cell with Hanks' and Ringer's solution at 37°C and 39.5°C. The samples, with a 600-grit surface finish, were subjected to a series of eight potential spikes, which disrupted the passive film. After each spike, the voltage was returned to the open circuit potential and maintained there for ten minutes. A decrease in current with time was an indication of repassivation, whereas, an increase in current with time indicated the onset of pitting. Success in biocompatibility was evaluated by comparing the tendency of each alloy to repassivate. The breakdown potential for Nitinol and 316L stainless steel was 0.3V and 0.2V respectively with the former displaying metastable pitting behavior. Maximum anodic currents recorded were 4.0 × 10 -5 Ams/cm 2 and 2.6 × 10 -3 Ams/cm 2 for Nitinol and 316 stainless steel respectively. It may be concluded that, under the same conditions, Nitinol is more resistant to pitting corrosion than 316L Stainless Steel.
