Laboratory investigation of microbiologically influenced corrosion of carbon steel in hydrotest using enriched artificial seawater inoculated with an oilfield biofilm consortium

© 2019 Elsevier Ltd Microbiologically Influenced Corrosion (MIC) is a major concern in hydrotest using untreated water. The hydrotesting process itself may last only hours, but the hydrotest water is often shut in for weeks or months. This allows biofilms to grow on pipe walls, which may eventually lead to pinhole leaks after the pipeline is commissioned. This laboratory study investigated MIC in hydrotest using an oilfield biofilm consortium to inoculate enriched artificial seawater to simulate hydrotest fluid. C1018 carbon steel coupons were placed in 120 mL anaerobic vials for incubation at 37 °C for up to 60 days. Experimental results showed that sulfate reducing bacteria (SRB), general heterotrophic bacteria (GHB) and acid producing bacteria (APB) formed robust biofilms on coupons that led to a weight loss of 7.1 ± 0.3 mg/cm 2 and maximum pit depth of 33.5 μm after 60 days. Electrochemical measurements were found to be consistent with the corrosion data

D-Tyrosine enhancement of microbiocide mitigation of carbon steel corrosion by a sulfate reducing bacterium biofilm.

Microbiocides are used to control problematic microorganisms. High doses of microbiocides cause environmental and operational problems. Therefore, using microbiocide enhancers to make microbiocides more efficacious is highly desirable. 2,2-dibromo-3-nitrilopropionamide (DBNPA) is a popular biodegradable microbiocide. d-Amino acids have been used in lab tests to enhance microbiocides to treat microbial biofilms. In this investigation, d-tyrosine was used to enhance DBNPA against Desulfovibrio vulgaris biofilm on C1018 carbon steel. After 7 days of incubation, the mass loss of coupons without treatment chemicals in the ATCC 1249 culture medium was found to be 3.1 +/- 0.1 mg/cm(2). With 150 ppm (w/w) DBNPA in the culture medium, the mass loss was reduced to 1.9 +/- 0.1 mg/cm(2) accompanied by a 1-log reduction in the sessile cell count. The 150 ppm DBNPA + 1 ppm d-tyrosine combination attained an extra 3-log reduction in sessile cell count and an additional 30% reduction in mass loss compared with 150 ppm DBNPA only treatment. The combination also led to a smaller maximum pit depth. Linear polarization resistance (LPR), electrochemical impedance spectrometry (EIS), and potentiodynamic polarization (PDP) tests corroborated the enhancement effects