Investigation of carbon steel corrosion by oilfield nitrate- and sulfate-reducing prokaryotes consortia in a hypersaline environment

Microbiologically influenced corrosion (MIC) behavior of the AISI 1020 carbon steel caused by consortia of nitrate-reducing prokaryotes (NRP) and sulfate-reducing prokaryotes (SRP) was investigated separately in hypersaline seawater conditions. Microbiological analysis, surface images, characterization of corrosion products, weight loss, and electrochemical measurements were employed to monitor the corrosion process for 10 days at 40 degrees C. Compared to abiotic corrosion (control), the extent of corrosion was more aggravated in the conditions with microbial consortia. It corroborates the critical role of microbial activity in corrosion processes in natural and industrial environments since microorganisms are widely spread. Corrosion rates obtained from Tafel extrapolation were statically equal for both microbial consortia (0.093 +/- 0.009 mm.y(-1)); however, the maximum pit depth on the steel surface subjected to NRP-MIC was about 25% deeper (48.5 mu m) than that caused by SRP-MIC (32.6 mu m). In contrast, SRP activity almost doubled the number of pits on the steel surface (2.7 x 10(4) +/- 4.1 x 10(3) pits.m(-2)), resulting in more weight loss than NRP activity. In addition, SRP cells formed nanowires to support direct electron uptake from steel oxidation. This research contributes to the understanding of steel corrosion mechanisms in hypersaline environments with the prevalence of NRP or SRP, as oil reservoirs undergo nitrate injection treatments.

Automated summary

Microbiologically influenced corrosion (MIC) of AISI 1020 carbon steel caused by nitrate-reducing prokaryotes (NRP) and sulfate-reducing prokaryotes (SRP) in hypersaline seawater conditions was studied. Microbiological analysis, surface imaging, corrosion product characterization, weight loss, and electrochemical measurements were conducted to monitor the corrosion process. The extent of corrosion was more severe in the presence of microbial consortia compared to abiotic corrosion. Both NRP and SRP showed similar corrosion rates, but NRP-MIC resulted in deeper pits on the steel surface while SRP-MIC caused more weight loss.