研究了近等原子比的镍钛合金在磷酸盐缓冲溶液(PBS)中亚稳态点蚀的电化学行为特征.极化试验表明,镍钛合金在磷酸盐缓冲液中具有良好的钝化性和耐蚀性;恒、动电位极化时,亚稳孔的形核数目和峰值电流均随着电位的升高而增加;随着温度的升高,镍钛合金的自腐蚀电位Ecorr、亚稳态点蚀电位Em、稳态点蚀电位Eb均线性降低,形成亚稳孔的数目也呈现减少的趋势.阻抗测试表明,当外加恒电位不超过镍钛合金点蚀电位时,镍钛合金的电化学阻抗谱为一容抗弧;当电位超过合金的点蚀电位时,出现Warburg阻抗,电极过程由电化学控制转变为扩散控制;腐蚀前后钝化膜阻抗变化明显.SEM表面形貌可以看到镍钛合金表面沿着磨痕沟槽产生的小孔.

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.