Microbiologically influenced corrosion of SUS304L and SUS316L welds caused by aerobic and anaerobic bacteria in groundwater (II)

摘要

Microbiologically influenced corrosion was suspected in a corrosion failure of stainless steel (SUS316L) piping, carrying saline groundwater. Laboratory simulation studies were planned to find out the mechanism of the corrosion. Culturing of bacteria strains in the ground water revealed 7 different species. Six of them were aerobic and one of them was anaerobic microbe that is Sulfate Reducing Bacteria (Desulfovibrio sp.). They were incubated separately in liquid medium and exposure studies were conducted. Formation of biofilm on SUS316L coupons was observed when they were exposed to the test solution with Comamonas sp., Sphingomonas sp., Agrobacterium sp., and Desulfovibrio sp. Pitting corrosion sites were observed on SUS316L coupons exposed in Desulfovibrio sp. inoculated solution. Corrosion potential of SUS316L coupons became noble when they exposed to the solution with Nutrient broth (NB). When SUS316L coupons exposed to the solution without NB and the sterile solution, the increasing of corrosion potential was not seen. The corrosion potential decreased when exposed to the aerobic microbes inoculated solution. However, in case of Desulfovibrio sp. inoculated solution, it stagnated in early stages, and increased after that. It was thought from the above result that Desulfovibrio sp. with aerobic microbes that are able to formed biofilm could influence this MIC.