划伤方法研究应力作用下硫代硫酸根对800合金再钝化动力学的影响

Repassivation Process on Stressed Alloy 800 in Simulated Crevice Chemistry Containing Thiosulfate

采用划伤方法研究应力作用下硫代硫酸根对800合金再钝化动力学的影响机理,采用C形环对试样进行应力加载。结果表明,划伤过程的最大电流与再钝化电流随电极电位的升高而升高,随着电位升高划伤部位的阳极溶解过程加快。与应力加载前对比,试样加载后划伤过程的最大电流与再钝化电流均增加,表明应力使金属的阳极溶解速度变快,同时使再钝化过程变难。硫代硫酸根可与应力协同阻止再钝化过程,这主要是由于硫代硫酸根的吸附与电化学还原成吸附硫,进而加快金属的溶解所致。

The repassivation kinetics of stressed Alloy 800 in simulated crevice chemistries containing thiosulfate is studied by scratch test, while the stress is exerted by a C-ring sample. Results indicate that, as the potential moves to anodic directions, the maximum current and repassivation current increase, which reveals that the anodic dissolution rate increases. Compared to the unstressed sample, the maximum current and repassivation current of the stressed sample are higher, indicating an increased anodic dissolution rate and a retarded repasivation process. The retard effect of thiosulfate on the repassivation of the alloy may be ascribed to that thiosulfate is adsorbed and then electrochemically reduced to elemental sulfur on the bare metal surface, which subsequently enhance the anodic dissolution.