稀土Ce对316L不锈钢耐腐蚀性能的影响

Effect of Rare Earth Element Ce on Corrosion Resistance of 316L Stainless Steel

采用失重分析,扫描电镜(SEM),能谱分析(EDS),电化学阻抗谱(EIS)和动电位极化实验(DP)等方法研究稀土元素Ce对316L不锈钢在3.5%(质量分数) NaCl腐蚀环境中耐腐蚀性能的影响。结果表明,添加适量的稀土元素Ce可有效减小316L不锈钢在3.5%NaCl溶液中的重量损失,降低其腐蚀速率,减小腐蚀表面点蚀坑的尺寸与数量,提高316L不锈钢在3.5%NaCl溶液中的腐蚀电位,降低其腐蚀电流密度,增大容抗弧半径,提高耐蚀性能。因此,本文确定提高316L不锈钢在3.5%NaCl溶液中耐腐蚀性能的最佳稀土元素Ce含量为0.015%(质量分数),并进一步揭示了Ce改善316L不锈钢耐腐蚀性能的主要原因:Ce可有效降低有害元素S在晶界处偏聚,净化晶界;改善夹杂物的形貌,减小夹杂物的尺寸。

Corrosion resistance of 316L stainless steels without and with addition of rare earth element Ce in 3.5%（mass fraction） NaCl solution was studied by means of mass change measurement,polarization curve measurement, EIS and SEM etc. Results show that the moderate addition of Ce can effectively decrease the mass loss and the corrosion rate of the 316L stainless steel, while diminish the size and quantity of corrosion pits on the steel surface. Accordingly, the moderate addition of Ce can reduce the corrosion current density, while enhance the free corrosion potential and the capacitive reactance of the steel. In other word, the moderate addition of Ce can enhance the corrosion resistance of the 316L stainless steel. Among others, the 316L stainless steel with the addition of 0.015%（mass fraction） Ce exhibits the best corrosion performance. The above beneficial effect of Ce addition may be ascribed to that rare earth Ce effectively reduce the segregation of S impurity at grain boundaries, refine the morphology of inclusions and decrease the inclusion size in the modified 316L stainless steel.