Evolution of passive film behavior on mechanically polished NiTi shape memory alloy during forward martensitic transformation

The corrosion property of Nickel-titanium (NiTi) shape memory alloy is investigated during forward martensitic transformation between 40C and 0C. The Differential Scanning Calorimetry technique is used to find the forward and reverse martensitic transformation temperatures. NiTi shows the present of martensitic phase at near room temperature by cooling from 80C. The change in corrosion behavior is monitored by electrochemical Open Circuit Potential (OCP) during phase transformation. Cyclic potentiodynamic polarization method is used to identify the corrosion compound of NiTi. Corrosion rate at each temperature extracted from polarization data and activation energy for corrosion reaction in martensite and austenite phase are calculated based on an Arrhenius relation between corrosion current density and reciprocal temperature.