Depassivation–repassivation behavior of type-312L stainless steel in NaCl solution investigated by the micro-indentation
Depassivation–repassivation behavior of type-312L stainless steel in NaCl solution investigated by the micro-indentation
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DOI：
10.1016/j.corsci.2008.11.020
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发表时间：
2009-07
影响因子：
8.3
通讯作者：
Takatoshi Yamamoto;K. Fushimi;M. Seo;S. Tsuri;Tetsuo Adachi;H. Habazaki
中科院分区：
文献类型：
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作者：
Takatoshi Yamamoto;K. Fushimi;M. Seo;S. Tsuri;Tetsuo Adachi;H. Habazaki
采用原位显微压痕技术研究了含钼6%的312L不锈钢、304和316L不锈钢在氯化钠溶液中的再钝化行为。通过辉光放电发射光谱(GDOES)对钝化膜的深度剖析，验证了在312L不锈钢表面形成的钝化膜的高稳定性。在296K的0.9moldm−3NaC l溶液中，316L和3304型不锈钢只有在0.3V(SHE)以下才发生钝化，超过0.3V(SHE)就会发生点蚀。相比之下，312L不锈钢没有发生点蚀。尽管三种不锈钢的耐点蚀性能有很大差异，但在0.3V(Se)下的显微压痕测试表明，三种不锈钢的再钝化动力学是相似的。不锈钢中钼的存在不影响再钝化动力学。使破裂的312L不锈钢表面重新钝化所需的电荷随着电位的增加而近似线性增加，即使在接近过钝化区的电位下钝化电流显著增加。不管钝化状态的稳定性如何，再钝化都不会伴随着钢的显著溶解。对在不同电位下形成的312L不锈钢钝化膜的深度剖析表明，钼物种在钝化膜的外层富集层，在外层之下存在富铬层。312L不锈钢外层含钼酸盐可阻挡氯离子的渗透，提高其抗局部腐蚀的能力。
Repassivation behavior of type-312L stainless steel containing 6% of molybdenum was examined in NaCl solution using in situ micro-indentation technique, together with type-304 and 316L stainless steels. High stability of the passive film formed on the type-312L stainless steel was also examined by depth profiling analysis of passive films using glow discharge optical emission spectroscopy (GDOES). In 0.9moldm−3NaCl solution at 296K the type-304 and 316L stainless steels are passive only up to 0.3V (SHE), above which pitting corrosion occurs. In contrast, no pitting corrosion occurs on type-312L stainless steel. Despite the significant difference of the pitting corrosion resistance, the repassivation kinetics of the three stainless steels, examined by micro-indentation at 0.3V (SHE), is similar. The presence of molybdenum in the stainless steel does not influence the repassivation kinetics. The charge required to repassivate the ruptured type-312L stainless steel surface increases approximately linearly with the potential, even though the passivity-maintaining current increased markedly at potentials close to the transpassive region. Repassivation occurs without accompanying significant dissolution of steel, regardless of the stability of passive state. Depth profiling analyses of the passive films on the type-312L stainless steels formed at several potentials revealed that molybdenum species enrich in the outer layer of the passive film, below which chromium-enriched layer is present. The permeation of chloride ions may be impeded by the outer layer containing molybdate, enhancing the resistance against the localized corrosion of the type-312L stainless steel.