Investigation of the Ag-Cu Ions' Effect on Microbial Activity of Sulphate Reducing Bacteria Leading to Corrosion

摘要

The microbiologically induced corrosion (MIC) of 316L stainless steel (SS) and the effects of Ag-Cu ions on microbial activities of Desulfovibrio sp. regarding to the corrosion of 316L SS were investigated. 316L SS coupons were exposed to the Desulfovibrio sp. cultures with and without Ag-Cu ions during 8, 24, 48, 72, 96, 120, 144, 168, 240, 360, 480, 600 and 720 h in a lab-scaled test systems. Control systems containing sterile Postgate's medium C (PC medium) without Desulfovibrio sp. in the absence and presence of Ag-Cu ions were set to work simultaneously with test systems. Test coupons were removed at each sampling time for enumeration of Desulfovibrio sp., determination of corrosion rate by the weight loss measurement method, and also carbohydrate and protein analysis from extracellular polymeric substances (EPS). Biofilm formation on the 316L SS surfaces were investigated by scanning electron microscopy (SEM). It was found out that Ag-Cu ions affected the growth curve of planktonic Desulfovibrio sp. and caused the entrance of planktonic cells to death phase earlier compared with the ions-free culture. In the presence of Ag-Cu ions, the amounts of carbohydrates and protein produced by Desulfovibrio sp. were significantly higher than that in the ions-free culture (respectively, p< 0.01 and p< 0.001). Desulfovibrio sp. was leading to corrosion of 316L SS in the presence and absence of Ag-Cu ions. However, results showed that Ag-Cu ions with the concentration of 0.3 ppm Cu and 0.13 ppm Ag, effected the metabolism of Desulfovibrio sp. and led to be more corrosive than ions-free culture.