In Vitro Corrosion Studies of Surface Modified NiTi Alloy for Biomedical Applications

This study evaluates the corrosion resistance and biocompatibility of surface modified NiTi alloy, which is widely used in biomedical applications due to its unique properties. The objective was to investigate the effects of surface modification techniques, specifically electropolishing followed by passivation, on the corrosion behavior of NiTi alloy. Methodology involved using a perchloric acid-based electrolyte for electropolishing under potentiostatic conditions, followed by passivation in an inorganic electrolyte. Characterization techniques, including scanning electron microscopy, atomic force microscopy, and X-ray photoelectron spectroscopy, were employed to analyze the modified surfaces. The results indicated that the passivated alloy exhibited a contact angle of 35.6°, approximately 58% lower than the mechanically polished sample, suggesting increased hydrophilicity. Electrochemical impedance studies demonstrated a threefold increase in barrier layer resistance for the passivated alloy, indicative of a more stable passive layer formed due to a thicker titanium oxide layer, which was about 18 times greater than that of electropolished samples. After immersion in Hanks’ solution for 1 day, the amount of nickel released from the passivated alloy was significantly reduced to 315 ppb, confirming enhanced stability of the passive layer and suggesting improved biocompatibility for biomedical applications.