Effect of Host Media on Microbial Influenced Corrosion due to Desulfotomaculum nigrificans
- PDF / 665,406 Bytes
- 9 Pages / 593.972 x 792 pts Page_size
- 89 Downloads / 194 Views
JMEPEG (2013) 22:1120–1128 DOI: 10.1007/s11665-012-0384-z
Effect of Host Media on Microbial Influenced Corrosion due to Desulfotomaculum nigrificans Suman Lata, Chhaya Sharma, and Ajay K. Singh (Submitted May 1, 2012; in revised form August 6, 2012; published online September 20, 2012) This article reports about the tests carried to investigate microbial-induced corrosion on stainless steels due to sulfate-reducing bacteria sp. Desulfotomaculum nigrificans in different host media. Stainless steel 304L, 316L, and 2205 were selected for the test. Modified BaarÕs media (BM), sodium chloride solution, and artificial sea water (SW) were used as test solutions in anaerobic conditions. Electrochemical polarization and immersion test were performed to estimate the extent of corrosion rate and pitting on stainless steels. SEM/EDS were used to study the details inside/outside pits formed on the corroded samples. Biofilm formed on corroded coupons was analyzed for its components by UV/Visible spectroscopy. Corrosion attack on the test samples was observed maximum in case of exposure to SW followed by NaCl solution, both having sulfide and chloride whereas stainless steel exposed to BM, having sulfide, showed minimum attack. Tendency of extracellular polymeric substances to bind metal ions is observed to be responsible for governing the extent of corrosion attack.
Keywords
Desulfotomaculum nigrificans, extracellular polymeric substances, sea water, sodium chloride, stainless steels
1. Introduction Sulfate-reducing bacteria (SRB), e.g., Desulfovibrio, Desulfotomaculum, and Desulfobulbus are anaerobic bacteria widely recognized to be among the most destructive microorganisms. They affect the materials through microbial influenced corrosion (MIC) causing localized attack on passive materials like stainless steels resulting in their unexpected failure (Ref 1-3). Such studies are important as they indicate about the possible bacterial attack through MIC on the industrial machinery in cases where these bacteria are likely to nurture. Thus, cooling circuits and power plant condensers of industrial plants are affected by MIC due to growth of these bacteria. To avoid it, chlorination has been used for preventing growth of biological organisms (Ref 4, 5). Stainless steel has been used increasingly for cooling water service in the chemical, petrochemical, and power utility industries because of its excellent corrosion resistance (Ref 6). However, in recent years, microbial activity is being recognized to play an important role in pitting stainless steel in many industrial environments (Ref 7). Sea water (SW) is used in many offshore industries for the cooling purpose and other activities. It contains higher amount of sulfide and chloride ions which promote corrosion of alloys (Ref 8, 9). Thus, corrosion on materials in these media could be due to combined effect of chemicals and the microbes together with the possibility of microbial activity getting influenced by the Suman Lata, Chhaya Sharma, and Ajay K. Singh, Materials Science Group, Depar
Data Loading...
