NaCl+HCl溶液中Ce对双相不锈钢腐蚀行为的影响

Effect of Ce on corrosion behavior of duplex stainless steel in NaCl+HCl solution

为了研究酸性NaCl溶液中双相不锈钢的耐腐蚀性能,以含微量稀土Ce的UNS S31803双相不锈钢为研究对象,采用电化学阳极极化和交流阻抗相结合的方法测试其在NaCl+HCl混合溶液中的耐腐蚀性能。利用扫描电镜(SEM)观测腐蚀后的形貌特征,采用电子探针(EPMA)检测合金元素与杂质元素的分布特征,分析Ce元素的加入对双相不锈钢电化学腐蚀行为的影响机制。结果表明,钢中存在两相的选择性腐蚀并伴有局部点蚀,其中铁素体相是腐蚀较严重的相;阳极极化测试与交流阻抗测试结果相吻合,Ce拓宽了试验钢的钝化区间;Ce通过净化钢液、降低S和P元素在相界的偏聚及使Cr、Ni和Mo等合金元素在两相中的分布更均匀等作用,提高了钢的耐腐蚀性能。

In order to study corrosion resistance of duplex stainless steels in acid NaCl solution,corrosion resistance of UNS S31803 duplex stainless steel containing Ce in NaCl+HCl solution was tested by electrochemical anodic polarization and electrochemical impedance spectroscopy(EIS).The morphological characteristics after corrosion were observed by scanning electron microscope(SEM),the distribution characteristics of alloying elements and impurity elements were detected by electron probe micro-analyzer(EPMA),and the effect mechanism of Ce containing in the duplex stainless steels on the electrochemical corrosion behavior was analyzed.The results indicate that there is selective corrosion of two phases and local pitting corrosion in steel,and ferrite phase suffers more serious pitting corrosion.The results of anodic polarization and EIS are agreed very well,and the passivation range increases because of adding Ce.The corrosion resistance is improved due to the purification of molten steel,the reduction of S and P segregation at the phase boundary and the more uniform distribution of alloy elements such as Cr,Ni and Mo in the two phases by the addition of Ce.