采用电化学阻抗谱(EIS)、极化扫描和循环伏安(CV)等电化学技术,结合SEM表面形貌分析技术,研究高强度低合金X80管线钢在富Fe酸性红壤环境中的硫酸盐还原菌(SRB)腐蚀行为及电化学过程。结果表明,酸性红壤环境中,环境适应期(前7 d) SRB对腐蚀电化学过程没有明显影响;SRB生长期的呼吸代谢活动导致X80钢的自然腐蚀电位降低,显著促进了管线钢的腐蚀过程;SRB通过胞外铁呼吸可与红壤颗粒表层FeOOH/Fe₂O₃等铁氧化物发生作用,引起FeOOH/Fe₂O₃的微生物异化还原,该过程中,SRB作为电子传输媒介,参与Fe和氧化铁间的电子转移,该机制是SRB促进局部腐蚀电化学过程的主要原因。提出了SRB促进红壤中管线钢微生物腐蚀(MIC)与胞外铁呼吸机制之间的联系。

Corrosion of buried pipeline in iron-rich clay mineral, such as the red soil, is a great issue for safety and economy concern in various industrial applications, e.g. oil/gas, water, sewerage disposal systems, which may partly attribute to the active Fe oxides constituents residing in the clay. Although various parameters on metallic corrosion in red soil have been widely studied, some soil properties affecting corrosion are still not fully understood, such as synergistic action of sulfate reducing bacteria (SRB) and Fe oxides in iron-rich clay. Anaerobic SRB, which reduce sulfate to sulfide, have long been associated with corrosion of steel and have been the focus of most research on biocorrosion. Recently, there have been numerous studies showing that SRB can reduce oxidized metals, such as Fe(III), Mn(IV), and some SRB are capable of coupling metal reduction to growth, so Fe(III) reduction in clay minerals by SRB will have great impacts on corrosion processes. Most of previous studies focused on the single parameter, such as microbial activities, Fe oxides, but neglected their synergistic action. In this work, to further mechanistic understanding the synergistic action between SRB and Fe oxides, the indoor immersed experiment was desinged. Open circuit potential (E_OCP), electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and polarization potential scanning were used to monitor the corrosion electrochemical process of the X80 pipeline steel electrode. Microscopic surface observation was studied by SEM. The results showed that, SRB had no significant effect on the electrochemical process during the environmental adaptation period (the initial 7 d). The decrease of E_OCP and electrochemical impedance (|Z|) of the X80 steel was resulted by the SRB iron respiration activity in the growing period, which significantly promoted the corrosion process of the steel. The SRB acts as an electron transport medium to participate in the electron transfer between Fe and iron oxide, which may lead to the electrochemical reduction of the iron oxides in the surface of red soil particles by the action of extracellular iron respiration, and it's the main reason to promote the local corrosion electrochemical process. The relationship between the corrosion of the material in the Fe-rich red soil and the microbial extracellular iron respiration was proposed.