采用扫描电化学显微镜( SECM)技术, 结合电导率和循环伏安测试, 研究了304不锈钢在NaCl溶液中的点蚀行为。结果表明, 点蚀早期阶段, 在不锈钢表面首先产生不稳定的电活性点; 点蚀形成的过程中, 这些电活性点或消失或成为稳定点蚀坑, 并同时出现新的电活性点。电活性点的产生与消失及点蚀的形成是同时发生的。NaCl溶液的电导率与其所含Fe2+浓度有关, Fe2+浓度越高, 超微电极探针检测到的稳态电流越大。

Pitting corrosion process of 304 stainless steel in NaCl solution was investigated using scanning electrochemical microscopy (SECM), combined with the measurements of electrical conductivity and cyclic voltammetry. The results showed that there were meta-stable electrically active sites on the surface of stainless steel in the initial pitting process. In the formation process of pits, some initiated meta-stable electrically active sites might disappear, some might propagate and finally become stable pits, while new ones might be induced. The generation, disappearance of meta-stable electrically active sites and formation of pits occurred simultaneously. The electrical conductivity of NaCl solution was related with the concentration of Fe2+ in the solution. The higher the concentration of Fe2+ in NaCl solution, the greater the steady-state current detected by superfine electrode probe.