Nitinol, a 50/50 alloy of nickel and titanium, is a shape-memory material that is widely used in the medical device industry.  Electrolytic polishing is a technique commonly applied to metals used in medical devices to remove defects and impurities in the oxide film as well as smooth and ensure greater uniformity of the surface and subsequently formed oxide.  The most widely used method for electropolishing nitinol includes  methanol/nitric acid at -30 oC.  The purpose of this work is to evaluate novel electropolishing conditions for nitinol that require less hazardous solutions and are favorable at room temperatures.  Nitinol wire was electropolished in a mixture of perchloric acid/acetic acid at room temperature.  Applied potential was varied between 30 and 60 V DC, and electropolish time was varied between 10 and 90 s.  The surface area of NiTi exposed to the solution was also varied.  The electropolishing conditions at 60 V DC and 90 s were effective in removing material and remodeling the wire surface to yield enhanced corrosion resistance by DC polarization scans.  However, repeated electropolishing with the same solution over time revealed greater corrosive effects toward the metal, indicative of perchlorate reduction and mediated by nickel(II) ion.

Efficacy of electropolishing nitinol with acetic acid/perchloric acid solutions

245th National Meeting (2013)

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