Adaptive bidirectional extracellular electron transfer during accelerated microbiologically influenced corrosion of stainless steel

Microbiologically influenced corrosion is a major source of degradation of metals. Here, extracellular electron transfer is studied during pitting corrosion of stainless steel in the presence of an electroactive bacterium and a riboflavin electron shuttle, revealing bidirectional electron transfer. Microbiologically influenced corrosion of metals is prevalent in both natural and industrial environments, causing enormous structural damage and economic loss. Exactly how microbes influence corrosion remains controversial. Here, we show that the pitting corrosion of stainless steel is accelerated in the presence of Shewanella oneidensis MR-1 biofilm by extracellular electron transfer between the bacterial cells and the steel electrode, mediated by a riboflavin electron shuttle. From pitting measurements, X-ray photoelectron spectroscopy and Mott-Schottky analyses, the addition of an increased amount of riboflavin is found to induce a more defective passive film on the stainless steel. Electrochemical impedance spectroscopy reveals that enhanced bioanodic and biocathodic process can both promote the corrosion of the stainless steel. Using in situ scanning electrochemical microscopy, we observe that extracellular electron transfer between the bacterium and the stainless steel is bidirectional in nature and switchable depending on the passive or active state of the steel surface.

Automated summary

Microbiologically influenced corrosion is a significant source of metal degradation, with the extracellular electron transfer playing a crucial role in pitting corrosion of stainless steel. The presence of a riboflavin electron shuttle can accelerate the corrosion process, leading to a more defective passive film on the steel surface when the riboflavin amount is increased.