Development of a model system to investigate the effects of surface roughness and media on marine biofilm formation and microbiologically influenced corrosion

The energy sector continues to face corrosion challenges, with significant pipeline failures due to microbiologically influenced corrosion (MIC). This study aims to develop a representative model system in which inoculae relevant to operating pipelines can be cultured to investigate biofilms and MIC on carbon steels. Two identical anaerobic CDC reactors ran simultaneously for 28 days; one
inoculated with a multi-species marine consortium and the other uninoculated. Carbon steel (UNS G10180) discs were used with two surface roughness profiles, Ra of 1.33±0.71 μm and 0.44±0.03 μm, as received and polished, respectively. Test media were either artificial seawater supplemented with yeast extract (1 g/L) or ATCC 1249 growth media. Molecular microbiological assessment, plus optical
analysis and electrochemical tests were performed (see Figure 1). As expected, biofilms have a marked impact on the corrosion mechanism and reactor environment. Sulfide concentrations initially increased in the inoculated reactors (523±118 μmol/L). Additionally, there was a negative shift in corrosion potential, attributed to microbe attachment and biofilm formation/growth. Localised and
shallow pits (see Figure 2) were clearly discernible in the biotic media, whereas only uniform corrosion was evident for the abiotic media. Electrochemical impedance was used to characterize the interfacial properties. This study provides insight into the role of biofilm formation on MIC and the importance
of using multiple lines of evidence (MLOE), incorporating a multidisciplinary approach to develop understanding of the mechanistic relationship between the biofilm and metallic degradation. These insights will support a move towards evidence-based biocide dosing and influence recommendations for new industry standards.