Metastable Pitting Behavior of Ni/Ti Alloy in Phosphate Buffer Solution

The metastable pitting characteristics of Ni/Ti alloy in phosphate buffer solution(PBS) was studied by electrochemical methods.Polarization experiments showed that the Ni/Ti alloy had good capabilities of corrosion resistance and passivation in PBS.During polarization,the number of metastable pits and the peak current increased with increasing potential.With increasing the temperature,the values of Ecorr,Em and Eb were lowered,and the number of metastable pits decreased.The EIS experiments showed that EIS arc was a capacitive reactance and the impedance modulus was large when the potential was less than the pitting potential of Ni/Ti alloy.With the increase of potential,the impedance modulus decreased.But when the potential was over the pitting potential,the corrosion products overflowed from the small holes and the electrochemical process was controlled by the concentration instead of activation.Deep pits in the Ni/Ti alloy were observed after the polarization experiments.