316L不锈钢焊缝腐蚀微电池的形成机理

Evolved Mechanism of Corrosion Micro-Cell at the Welding Seam of 316L Stainless Steel

为了探究316L不锈钢焊缝腐蚀微电池的形成机理,通过微观组织观察及电化学试验进行了分析。采用扫描电镜(SEM)对焊件三区(焊缝区、热影响区、母材区)的形貌及元素组成进行了观察分析,采用金相显微镜观察微观组织,并确定晶粒度及非金属夹杂物及其分布。结果表明:316L不锈钢焊缝形成腐蚀微电池的倾向与元素组成、非金属夹杂物和晶粒度大小等因素紧密相关;焊缝三区腐蚀电位、腐蚀电流不同,耐蚀性能差异较大,因而腐蚀电位最低的热影响区与腐蚀电位最高的母材区在电解液中比较容易形成腐蚀微电池,且热影响区可视为此微电池的阳极,腐蚀进程较快。

In order to study the evolved mechanism of micro-cell corrosion formation at the welding seam of 316L stainless steel,the microstructure observation and electrochemical analysis were employed.The morphology and element composition of welding three-zones containing weldmetal zone,heat-affected zone and base metal zone were observed and analyzed by scanning electron microscope （SEM）,and the metallographic microscope was used to characterize the microstructure and ascertain the grain fineness,non-metallic inclusion and their distribution.Results showed that the formation of corrosion micro-cell at the welding seam of 316L stainless steel was closely related to element composition,non-metallic inclusion and grain size.At the different zones,the corrosion potentials and corrosion current densities were different,and the corrosion resistance differed greatly.Therefore,the heat-affected zone with the lowest corrosion potential and base metal zone with the highest corrosion potential could easily make up corrosion micro-cell,and the heat-affected zone regarded as the anode of micro-cell was corroded faster.