Fe2+对碳钢硫酸盐还原菌腐蚀行为的影响

对比分析了Q235钢在无Fe2+的接菌培养基和Fe2浓度为30mg/L的接菌培养基中的腐蚀行为.使用光学显微镜跟踪观察Q235钢在两种介质中的表面形貌随时间的变化,用电化学阻抗谱研究Q235钢在两种培养基中的电化学行为.用聚焦离子束显微镜制作Q235钢在两种培养基中的腐蚀产物剖面,并用能谱对腐蚀产物进行成分分析.对电化学阻抗谱所得结果进行拟合,结果表明,Fe2会使Q235钢表面形成的生物膜电阻降低,电容升高,Q235钢反应电阻保持较低,从而使反应持续进行,铁不断溶解.培养基中加入30mg/L的Fe2+后,Q235钢表面附着的细菌显著增多,形成的生物膜厚而疏松,膜中混合有腐蚀产物硫化物,膜下的金属出现众多微小的点蚀.电化学阻抗谱拟合结果与形貌观察及成分分析结果吻合,Fe2+对Q235钢的SRB腐蚀反应具有催化作用.

Effect of Ferrous Ion on Sulfate-reducing Bacteria Influenced Corrosion of Mild Steel

In this investigation,we analyse the corrosion behavior of mild steel immersed in two inoculated cultures with different ferrous concentration-0mg/L and 30mg/L.The optical microscope and electrochemical impedance spectroscopy(EIS) were used to obtain the photos and EIS data of mild steel with different immersing time.The Focus Ion Beam(FIB) was used to observe and cut the corrosion products of mild steel.The EDS was used to analysze the composition of corrosion products.The EIS data was analyzed with equivalent circuit.According to The result of the analysis,the resistance of the biofilm formed on the surface of mild steel immersed in the culture without ferrous ion(sample I) was higher than that immersed in the culture with ferrous ion(sample II).On the contrary,the capacitivity of the biofilm formed on the surface of sample I was lower than that of sample II.From the FIB photos we can learn that compared with sample I,the amount of sticking SRB on the surface of sample II was greater,the biofilm formed on sample II was thicker and was more loose,the corrosion of sample II was more serious.With respect to the EDS result,there is S in the biofilm formed on sample II.To sum up the above,the result of EIS dovetailed with the results of optical microscope、FIB and EDS.Ferrous can speed up the SRB influenced corrosion of mild steel.