静水压力对Fe-20Cr合金点蚀行为的影响

基于统计学方法和随机理论，利用动电位极化曲线和恒电位测试技术研究静水压力对Fe-20Cr合金点蚀行为的影响。随着静水压力的增加， Fe-20Cr合金的击破电位降低，维钝电流密度减小，耐蚀性能变差。静水压力对Fe-20Cr合金点蚀产生和点蚀生长的研究表明：高的静水压力下，亚稳态点蚀发生的频率加快且向稳态点蚀发展的倾向增大，从而导致点蚀的产生速度加快，点蚀的孕育期缩短，但点蚀的产生机制并没有发生改变；静水压力的增加增大了点蚀的生长概率，高压下产生的点蚀更容易成长为大的腐蚀坑。

INFLUENCE OF HYDROSTATIC PRESSURE ON THE PITTING BEHAVIOR OF Fe-20Cr Alloy

The effect of hydrostatic pressure on pitting behavior of Fe-20Cr alloy in 3.5% NaCl solution was investigated by means of potentiodynamic polarization and potentiostatic technology. For the polarization curve measurement, the specimens were kept for 1 h in the NaCl solution at various hydrostatic pressures and then scanned in 0.333 mV/s, 3 mV/s, and 5 mV/s scan rate respectively. For the induction time measurement, the specimen was pretreated in Na₂SO₄ solution at a constant potential, -0.22 V, for 500 s. After pretreatment, the specimen was kept in the NaCl solution at various hydrostatic pressures, and a potentiostatic technique\linebreak(-0.22 V) was used to measure the anodic current trace. Experiment data was analyzed based on statistical and stochastic approaches. With the increasing of hydrostatic pressure, the pit corrosion resistance of Fe-20Cr alloy was deteriorated, which was distinguished by the decrease of E_crit and the increase of passive current density.The results also showed that there were obvious effects on processes of pit initiation and pit growth of Fe-20Cr alloy: (1) the pit generation rate was evidently increased compared with that under lower hydrostatic pressure resulting from the metastable pits' frequent initiation and increased tendency to stable pits. However, it seemed that pit generation mechanism showed no hydrostatic pressure dependence. (2) the probability of pit growth increased with the increasing of hydrostatic pressure, which implied that the metastable pit on Fe-20Cr alloy exhibited higher probability to become larger pit cavity during the same time interval than that under lower hydrostatic pressure.