Sulfate-reducing Bacteria Influenced Corrosion Of Marine Steel And Its Control

In this paper, sulfate-reducing bacteria (SRB) influenced corrosion of marine steel and its control in seawater and sea mud environments were studied, concerned of corrosion mechanism, occurrence and transformation process of corrosion products and the influence of cathodic protection on corrosion of steel in sea mud containing SRB.SRB was cultured and enriched originated seamud from Jiaozhou Bay, Qingdao. Desulfotomaculum was identified by molecule biology analysis and morphology of SRB was observed by fluorescence microscopy and transmission electron microscopy(TEM).The corrosion-restrained to corrosion-accelerated process of marine steel was studied in seawater and sea mud environments containing active SRB by weight-loss and galvanic corrosion methods, electrochemical impedance spectra(EIS), electronic probe microanalyzer(EPMA) and TEM, including the attachment of SRB, transformation of oxides to sulphides influenced by SRB metabolic products, and morphology and composition identification of corrosion products. Besides, formation and extension of pitting corrosion influenced by SRB from the point of view of corrosion interface between substrate and corrosion products and biomineralization of single crystalline ferric oxide cube in medium inoculated SRB were also discussed. The reliability of cathodic protection on carbon steel buried in sea mud containing SRB was evaluated with emphasis on EIS under different cathodic protection potentials. The relationship among cathodic protection potential, corrosion rate and bacteria activities was summarized by EIS results, weight-loss test and number-calculation of bacteria by most probability number(MPN) method. -950mV (CSE) or even lower potential was needed to ensure of effective protection. The growth activities and stability of SRB were low under higher cathodic protection potential.