Electroactive Bacteria Associated With Stainless Steel Ennoblement in Seawater

Abstract

Microorganisms can increase the open-circuit potential of stainless steel immersed in seawater of several hundred millivolts in a phenomenon called ennoblement. It raises the chance of corrosion as the open-circuit potential may go over the pitting corrosion potential. Despite the large impact of the ennoblement, no unifying mechanisms have been described as responsible for the phenomenon. Here we show that the strict electrotroph bacterium “Candidatus Tenderia electrophaga” is detected as an ennoblement biomarker and is only present at temperatures at which we observe ennoblement. This bacterium was previously enriched in biocathode systems. Our results suggest that “Candidatus Tenderia electrophaga,” and its previously described extracellular electron transfer metabolism coupled to oxygen reduction activity, could play a central role in modulating stainless steel open-circuit potential and consequently mediating ennoblement.

Influence of dissolved oxygen content on the bacteria‐induced ennoblement of stainless steels in seawater and its consequence on the localized corrosion risk

“…Above 100 ppb of DOC, biofilm‐induced ennoblement was detected, increasing the risk of localized corrosion, and therefore promoting the use of more resistant alloys. The bacteria correlated with the ennoblement were related to hydrocarbon‐degrading bacteria, which were also found in another study about the role of temperature on the bacteria‐induced ennoblement, and associated with electroactive bacteria by other authors . Future studies should consider and further investigate the role of hydrocarbon‐degrading bacteria to understand their relation with the ennoblement of stainless steel.…”

“…Among the biomarkers, some are related to the known hydrocarbon‐degrading bacteria like Alcanivorax , Polycyclovorans , Algiphilus , and Thalassolituus . It should be noticed that this type of bacteria was also identified in a study about the temperature effect on stainless steel ennoblement . A member of the Alcanivoraceae family was also found in a biocathode experiment where bacteria are fed by a cathode as a sole electron donor source .…”

“…These results suggest that the microorganisms responsible for the ennoblement are probably not of the same nature worldwide, or that they adapt to the different local environments. The nature of the bacteria associated with the ennoblement was investigated in another study and suggests the involvement of electrotrophic bacteria, which are able to catalyze the oxygen reduction with the current provided by the cathode …”

A graphenic and potentiometric sensor for monitoring the growth of bacterial biofilms

“…This study showed a negative correlation between bacterial growth on the working electrode surface and OCP, with a significant reduction of this latter during the exponential phase. Previous studies demonstrated that the direction of the potential change depends on the microorganism, the material where the biofilm develops and the environment [42,56]. Here, the OCP shift towards more negative values as the bacterial concentration increases may be explained by the interaction of a variety of factors.…”

Electrochemical Bacterial Enrichment from Natural Seawater and Its Implications in Biocorrosion of Stainless-Steel Electrodes

“…Indeed, biocorrosion of SS has been linked with the action of autotrophic metabolism [36][37][38]. This type of corrosion is frequently associated with the ennoblement of the OCP involving iron-oxidizing bacteria, manganese-oxidizing bacteria [36,38], and, more recently, electro-autotrophic bacteria able to use an electrode (i.e., a SS coupon) as the electron donor to reduce oxygen [37,39,40]. Furthermore, the ennoblement of SS plates exposed to natural seawater typically shifts the OCP by +200 to +300 mV (vs. Ag/AgCl), bringing it closer to the pitting corrosion potential [37].…”