316L不锈钢在南海环境中的缝隙腐蚀行为研究

目的研究316L不锈钢在南海环境中的缝隙腐蚀行为。方法利用自主设计的实海实验装置,在南海170m水深的位置开展316L不锈钢缝隙腐蚀实验。利用光学显微镜观察试样的腐蚀形貌,利用扫描电子显微镜(SEM)观察腐蚀产物膜的微观形貌,结合能谱仪(EDS)分析腐蚀产物膜的微区成分,并利用荧光显微镜观察缝隙腐蚀试样表面微生物的附着情况。通过对比点蚀试样与缝隙腐蚀试样的腐蚀形貌,并观察缝隙腐蚀试样腐蚀形貌随腐蚀时间的变化,分析研究316L不锈钢在南海环境中的缝隙腐蚀行为。结果实海工况下浸泡120 h后,点蚀试样腐蚀轻微,机械划痕清晰可见,缝隙腐蚀试样表面有腐蚀产物生成,并出现明显的局部损伤。随着腐蚀时间的延长,缝隙腐蚀试样表面的局部损伤发展为浅表局部腐蚀,缝隙口堆积锈红色腐蚀产物,并形成闭塞电池。腐蚀408h后,在Cl~-的催化及微生物膜的加速作用下,缝隙口生成许多细小的点蚀坑,并聚集形成点蚀带,缝隙内部呈现波纹状腐蚀形貌,缝隙外部腐蚀相对轻微。荧光照片可见缝隙腐蚀试样表面有微生物附着。结论316L不锈钢在南海环境中具有较高的缝隙腐蚀敏感性。

Crevice Corrosion of 316L Stainless Steel in Coastal Waters of South China Sea

The aim of this study is to investigate the crevice corrosion of 316 L stainless steel in coastal water of South China Sea.Crevice corrosion and pitting corrosion samples were immersed in coastal waters at the depth of about 170 m in South China Sea.Optical microscope,scanning electron microscopy,energy-dispersive spectrometry and fluorescence test were carried out to characterize the corrosion products of 316 L stainless steel.The results showed that 316 L stainless steel is susceptible to crevice corrosion in marine environment.After the initial 120 h of immersion,corrosion products and localized damage were observed on the crevice sample surface,while scratch marks were still clearly visible on the pitting sample surface.As the dissolved oxygen inside crevice depleted at the initial stage and the oxygen outside was difficult to diffuse inward,an oxygen concentration cell formed between the parts of steel insides and outside crevice,then the crevice corrosion was promoted.Because of the catalysis of Cl~-ions and metabolism of microorganism,steel inside crevice suffered from pitting corrosion.Corrosion products accumulated and a groove formed at crevice mouth after a longer period of immersion.