Corrosion Resistance and Biocompatibility of Passivated NiTi

Equiatomic nickel-titanium (NiTi) or Nitinol possess a unique combination of properties, including superelasticity and shape memory, which are very attractive for biomedical applications. NiTi has been used in orthopedic and orthodontic implants for several decades and has contributed to significant improvements in these fields [1, 2]. This alloy is rapidly becoming the material of choice for selfexpanding stents, graft support systems, filters, baskets and various other devices for minimally invasive interventional procedures (Fig. 1) [1,3]. While the superior performance of NiTi over conventional engineering materials for implants is well documented [1,4,5], the high nickel content of the alloy (55 weight % Ni) and itspossible influence on biocompatibility continues to be an issue of concern. This concern is further complicated by the conflicting literature on corrosion resistance.

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