Multiphysics Modeling of Biochemical Interactions in Sulfate-Reducing Bacterial Biofilms and Their Effects on Carbon-Steel Corrosion

Sulfate-reducing bacteria (SRB) are anaerobic microorganisms that use sulfate as aterminal electron acceptor and generate reduced sulfur species, including bisulfide andhydrogen sulfide. Within biofilms on steel, biological activity interacts with transport, electrochemistry, mineral precipitation, and surface evolution. These coupled processes can accelerate localized corrosion or, under certain conditions, contribute to mineral layers that partly inhibit corrosion. This paper reviews key biochemical and electrochemical interactions involved in SRB-associated corrosion and proposes a continuum modeling framework coupling microbial growth, sulfate reduction, biofilm transport, aqueous speciation, iron dissolution, electron transfer, and mineral formation.The framework combines species-conservation equations, dual-substrate Monod kinetics, ionic transport, interfacial electrochemical kinetics, and Faraday’s law. A phase-field or moving-boundary formulation is proposed for representing localized metal loss. Cathodic depolarization, biocatalytic sulfate reduction, and extracellular electron transfer are treated as potentially coexisting mechanisms rather than universally exclusive explanations.The paper also identifies requirements for parameter estimation and validation, includingchemical profiles, electrochemical measurements, biofilm characterization, and localizedcorrosion measurements. The proposed equations define a research framework; quantitative prediction requires system-specific experimental calibration and independent validation.