Inhibiting Biocorrosion of Pipeline Steel in the Presence of Zinc Molybdate Nanocrystals within a CO2 Saturated Desulfovibrio Desulfuricans bacterial Culture Under Carbon Source Deprivation

Abstract

Even with limited organic carbon sources in oilfields, the presence of sulphate reducing bacteria (SRB) intensifies microbiologically influenced corrosion (MIC), consequently leading to compromised material integrity. On pipeline steel substrates with active biofilms, Feo is subsequently utilized as an alternative donor by SRBs during energy metabolism. In this work, the survival of Desulfovibrio desulfuricans (ATCC 27774) SRB cells and their impact on the pipeline steel (API 5L X70) corrosion within simulated CO2-saturated oilfield-produced water with different concentrations of organic carbon source have been investigated. Cell counts reduced with the level of carbon source reduction after incubation, but more cells survived at moderate carbon starvation compared to extreme conditions. To combat MIC, we have introduced different concentrations of zinc molybdate (ZnM) crystals against bacterial growth, synthesized from a new chemical route. The rate of MIC reduces more than 80 times in the presence of ZnM crystals under anaerobic conditions, and this has been attributed to the cellular growth inhibitive effect of ZnM. The extent of SRB colonization of steel was monitored within duration of study using confocal laser scanning microscopy after staining with appropriate Live/Dead dyes. Steel biocorrosion mechanism is elucidated by means of electrochemical impedance spectroscopy, potentiodynamic polarization and surface analyses. Adhering corrosion products on steel in the presence of D. desulfuricans biofilm are predominantly FeO films and FeS/MnS aggregates; this has been confirmed by X-ray photoelectron spectroscopy. Severe anodic steel dissolution is observed on steel within the test culture without ZnM, and this is attributed to SRB-led MIC and CO2 corrosion. Here, the energy needed for cellular survival was harnessed by a combination of Feo oxidation and sulfate reduction even after carbon source starvation. The degree of biocorrosion inhibition increases with ZnM crystal concentration and as more bacterial cells die off within the culture media.