硫质量分数对船体钢诱发点蚀行为的影响研究

Effect of sulfur on pitting corrosion behavior of hull steel

采用腐蚀浸泡的方法研究了酸性氯离子环境下S质量分数对低合金船板钢耐蚀性的影响,探讨了非金属夹杂物诱发点蚀形核的机理。结果表明,杂质元素S对钢的耐蚀性具有不利影响。随着S质量分数的增加,钢的耐点蚀性能恶化。S元素损害耐蚀性主要与钢中的非金属夹杂物有关。不同种类夹杂物诱发点蚀的机理有显著差异。单一Mn S夹杂物与基体间存在缝隙,其诱导点蚀形核包括缝隙腐蚀和夹杂物溶解两个过程,Mn S夹杂物是最敏感的点蚀诱发源;MXS-Al_2O_3复合夹杂物同样能诱发低合金钢的点蚀形核,包裹在Al_2O_3外层的硫化物优先发生溶解,成为腐蚀介质的通道,从而引发局部腐蚀。Mn S-Al_2O_3夹杂物的点蚀形核能力大于Ca S-Al_2O_3夹杂物,Ca S遇到水容易发生水解并在夹杂物周边形成OH-,阻碍了坑内部的酸化,有利于抑制钢的耐局部腐蚀性能。

This paper was based on the media of 10% NaC1 solution whose pH was 0.85, and the effect of sulphur con- tent, the non-metallic inclusion on the corrosion behavior were studied. Results indicated that sulphur shows negative ef- fect for the corrosion resistance of steel. The pitting resistance worse with sulphur content increases, which is mainly at- tribute to the non-metallic inclusions in steel. There is significant difference for the mechanism of pitting initiation be- tween different kinds of inclusions. A micro-gap exists between substrate and single MnS inclusions, the pitting initiation processes of MnS contains the crevice corrosion and the dissolution of inclusions, MnS were seen to be the most sensi- tive inclusion to pitting corrosion; The pitting corrosion also can be induced by MxS-ALO3 composite inclusions, MxS which wrapped in the outer layer of Al2O3 dissolved preferentially, and which become the channels of corrosive media, then causing localized corrosion. The pitting nucleation sensitivity of MnS-A1203 is greater than CaS-Al2O3 inclusions. Ca treatment is an effective way to improve the resistance of localized corrosion. CaS is prone to hydrolysis in water and the formation of OH- around the inclusions hinders the acidification in the pit, and is beneficial to restrain the local corrosion resistance of the steel.