如图 1(a) 所示，在不同的浸泡时间后，开路电位 (OCP) 值在整个测试过程中经历了频繁的变化。 OCP 的演变，即进行 EIS 测量的值，总结在图 1（b）中。 很明显，由于浸泡过程中腐蚀产物的形成，浸泡后的所有OCP值都高于0h时的值。 还可以看出，48 h、240 h 和336 h 的OCP 值逐渐下降，其趋势与其他曲线不同。 这种现象可能归因于样品表面腐蚀产物的分解。 OCP 在不同浸泡时间的变化表明样品表面的成分或形态不断变化。

As shown in Fig. 1(a), after different immersion periods, theopen circuit potential (OCP) values underwent frequent variationsthroughout the tests. The evolution of OCP, the values at which theEIS measurement was carried out, was summarized in Fig. 1(b). Itwas obvious that all the OCP values after immersion were higherthan that at 0 h due to the formation of corrosion products in thecourse of immersion. It also can be seen that the OCP values for 48 h,240 h and 336 h decreased gradually, the trends of which were dif-ferent from other curves. The phenomena may be attributed to thebreakdown of the corrosion products on sample surfaces. The vari-ations of OCP at different immersion period indicated the constantchange in composition or morphology of the sample surfaces.