Low-Voltage Polarization in AOT Solution to Enhance the Corrosion Resistance of Nitinol

Abstract

In this work, the corrosion behavior of bare nitinol (NiTi) alloy in Ringer's solution containing different concentrations of sodium bis(2-ethylhexyl) sulfosuccinate (AOT) was first studied in order to determine whether the surfactant acts as a corrosion inhibitor. Results of potentiostatic and potentiodynamic experiments allowed concluding that AOT is a pitting corrosion inhibitor for NiTi. In a second stage of this research work, NiTi was treated under potentiostatic control (2.00 V) for 1 h in 0.10 M AOT solutions of pH 8.4 and 12. Static and rotating electrodes were used. The influence exerted by this treatment on the passive behavior of the alloy was studied in Ringer's solution using different electrochemical and surface analysis techniques. The best anticorrosion performance was obtained using a rotating electrode and AOT solution of pH 8.4. The thin oxide layer grown potentiostatically consists of TiO2, while no Ni was found in the outermost layer. The presence of this oxide layer allows reducing the amount of Ni and Ti released at open circuit potential conditions and at very positive potentials where pitting corrosion of the bare alloy occurs.