Impact of Desulfovibrio alaskensis biofilms on corrosion behaviour of carbon steel in marine environment

• SRP metabolic activity causes corrosion potential changes during biofilm formation.
• D. alaskensis corrosiveness depends on the way of its contact with the surface.
• SRP biofilms cause pitting of carbon steel.
• Extracellular proteins may be vital for surface colonisation and biofilm formation.

Sulfate reducing prokaryotes are associated with the steel deterioration. They build heterogeneous biofilms, capable of accelerating corrosion processes. In this study metabolic activity and the biofilm development of Desulfovibrio alaskensis were correlated to electrochemical response of carbon steel surface. In the exponential growth phase sulfide concentration reached its maximum of about 10 mM. This phenomenon was responsible for the parallel increase in the corrosion potential (Ecorr) up to − 720 mV (vs. SCE). Subsequently, during the intensive biofilm formation and development another Ecorr peak (− 710 mV vs. SCE) occurred. Decrease in Ecorr was registered during the biofilm maturation and kept stable, being 20 mV lower than in the control. While carbon steel was protected from the microbial attachment and exposed to metabolic products, only one potential maximum (− 730 mV vs. SCE) was recorded. Here Ecorr variations coincided with sulfide concentration changes and kept at 120 mV lower vs. the control. Weight loss examinations revealed corrosion rates, which did not exceed 0.05 mm/y. Confocal microscopy suggested the importance of extracellular proteins in the biofilm formation. Above 150 proteins were detected in the EPS matrix. Surface effects of biofilm and metabolic products were visualised, revealing the role of attached microorganisms in the localised corrosion.