Microbiologically influenced corrosion (MIC) is one of typical reasons leading to a lot of damage of pipeline steels in the shale gas environments. MIC behavior and mechanism studies are important towards to steel protection. In this work, Citrobacter amalonaticus, a corrosive bacterium, was isolated from a shale gas well of China. And the corrosion behavior of N80 steel caused by C. amalonaticus was studied in simulated shale gas produced water at 60 °C making use of weight loss, surface analysis, electrochemical impedance spectroscopy (EIS), anodic potentiostatic polarization measurements, and potentiodynamic polarization curves. Results demonstrate that C. amalonaticus could accelerate the uniform and localized corrosion rates of N80 steel at 60 °C with values of (0.221 ± 0.016) and (0.557 ± 0.062) mm/y, respectively. Experimental results suggested that the adsorption of an organic inhibitor film on steel surface caused the corrosion rates of abiotic specimens going down. However, the existence of C. amalonaticus inhibited the adsorption of organic inhibitor film. The adhesion and biofilm formation of C. amalonaticus contributed to steel corrosion acceleration. The nucleation and growth of metastable pitting were enhanced by C. amalonaticus, thus causing a severe localized corrosion.
Keywords: Citrobacter amalonaticus; Localized corrosion; Microbiologically influenced corrosion; N80 steel; Shale gas.
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