Nitinol surface characteristics and corrosion behavior in different passivation media

In this study different passivation methods effect on the corrosion of the nitinol stents was investigated. All samples were electropolished, and then passivated by the following methods, hot air, HNO₃, H₂O₂ and a combination of HNO₃ and hot air. To understand the influence of the passivation on the corrosion resistance of nitinol, this study included oxide characteristics on different samples using TOF-SIM analysis of the surface. Electrochemical corrosion techniques have been used to evaluate the corrosion behavior of nitinol wire stents. A model of the corrosion vs the oxide characteristics on finished surface has been made. Results show that there are significant variations in the corrosion resistance of samples passivated with different methods. This same variation has been observed in oxide characteristics as well. Among all passivated samples H₂O₂ shows higher corrosion resistance than the other samples.