Microbiologically Influenced Corrosion Behavior Of Friction Stir Welded S32654 Super Austenitic Stainless Steel In The Presence Of Acidithiobacillus Caldus Sm-1 Biofilm

The microbiologically influenced corrosion (MIC) susceptibility of friction stir welded (FSW) S32654 super austenitic stainless steel (SASS) in the presence of acid producing bacterium Acidithiobacillus caldus SM-1 was investigated by surface analysis techniques and electrochemical measurements. The average depth of pits shown on the FSW coupon surface was 2.8 +/- 0.5 mu m after 14 days of immersion in A. caldus SM-1 broth, which was similar to that of the control base metal (BM) coupon (2.7 +/- 0.6 mu m). The results of electrochemical measurements showed that control BM and FSW coupons had very close corrosion rates in both abiotic and biotic media. The results indicated that the FSW process did not decrease the corrosion resistance of S32654 SASS. In addition, A. caldus SM-1 significantly accelerated the general corrosion and pitting corrosion of control BM and FSW coupons. The lowest pH value of A. caldus SM-1 inoculated medium arrived at 1.81 +/- 0.09 after 14 days of incubation. The acceleration of corrosion rate may be attributed to the generation and enrichment of aggressive acidic metabolites of A. caldus SM-l underneath the biofilm.