Microbially Influenced Corrosion of various types of stainless steel welds and joints.

在污水处理厂启动后的短短两个月内，焊缝就发生了故障。在失效分析开始时，认为裂纹腐蚀是焊接缺陷的主要原因。但是，估计焊缝的腐蚀速度太快了。然后，进行了冶金失效分析，以了解这种行为。最后得出焊缝局部腐蚀是一种微生物影响腐蚀（MIC）的结论。利用不锈钢焊缝和从受mic影响的污水处理厂获得的残液进行了实验室规模试验的第一阶段。测试样品暴露在液体中，并在恒温培养箱中保存。在316L、308N（约0.2%质量氮）和308焊缝金属上发现了腐蚀坑。在腐蚀坑附近观察到大小不一的细菌菌落，并对细菌类型进行了鉴定。对鉴定出的细菌进行了腐蚀能力评价试验。评价了所用不锈钢的MIC敏感性。

The failure in the weld joint occurred in as little as, two months from the start-up of the sewage treatment plant. At the beginning of the failure analysis, crevice corrosion was considered as the main reason since the welding defects. But, the estimated corrosion rate of the welds was too fast. Then, metallurgical failure analysis to understand this behavior was carried out. Finally, it was concluded that the localized corroion on the welds was a kind of Microbiologically Influenced Corrosion (MIC).The first stage of a laboratory scale test using the stainless steel welds and the residual liquid obtainable from the MIC-affected effluent treatment plant was performed.The test samples were exposed in the liquid and kept in an incubator at constant temperature. Corrosion pits were found on 316L,308N (0.2% mass nitrogen approximately) and 308 weld metal. The colonies of bacteria several mum in size near the corrosion pits were observed and the types of the bacteria was identified. The evaluation test of corrosion ability of the identified bacteria was planned. MIC susceptibility of the stainless steels used was evaluated.