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Corrosion Behavior of NiTiCo High Stiffness Shape Memory Alloys

Xu Huang, Dennis W. Norwich, and Michael Ehrlinspiel, Memry Corporation, Bethel, CT, USA

The corrosion behavior of high stiffness NiTiCo shape memory alloys was systematically investigated in the present study including straight wires, wire formed stents, and laser cut stents.  It was found that the corrosion behavior of NiTiCo alloys is comparable to that of binary NiTi.  This is attributed to the small amount of cobalt used in the ternary alloy.  Additionally, the corrosion resistance of high stiffness NiTiCo shape memory alloys is independent of the stent forming method.  To explore the galvanic corrosion susceptibility between NiTiCo and binary NiTi alloys, a NiTi sleeve was laser welded to a NiTiCo stent.  There was no galvanic corrosion observed in this NiTiCo-NiTi component even after the component was immersed in a phosphate buffered saline (PBS) solution at 37°C for three months.  This study will shed some light on the industrial applications of high stiffness NiTiCo shape memory alloys.

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