The corrosion behaviour of mild steel (MS) was systematically investigated as a function of the alkyl chain length in the cation of 1-alkyl-3-methylimidazolium tricyanomethanide ([Cnmim]TCM, n = 2, 4, 6 and 8) ionic liquids (ILs) with respect to their potential application as a structural material and solvents for CO2 capture plants respectively. The surface of MS was examined by scanning electron microscopy, energy dispersive X-ray spectroscopy and micro-Raman mapping before and after immersion testing at temperatures of 70 and 80 °C for durations varying from 1 hour to 10 days. Corrosion initiates at the sites of MnS inclusions on the surface of MS, resulting in the formation of cavities due to the MnS dissolution, which may be surrounded by corrosion products containing magnetite (Fe3O4) and maghemite (γ-Fe2O3). The amount of the corrosion products generated around the inclusion sites decreased with the increase of the cation alkyl chain length, following the order [C2mim]TCM > [C4mim]TCM > [C6mim]TCM ≈ [C8mim]TCM. This was attributed to the corrosion inhibition effect of the ILs through adsorption on the metal surface and blocking active sites, with the inhibition efficiency increasing with the alkyl chain length. The underlying mechanism was associated with corrosion processes at active sites on the MS surface, such as sulphide inclusions, in the presence of residual water and oxygen in the IL. It was shown that increase of the water content in the ILs to about 50 000 ppm resulted in faster dissolution of the MnS inclusions. Finally, it was demonstrated that removal of oxygen from the IL significantly reduced the corrosion rate.
针对 1-烷基-3-甲基
咪唑鎓三
氰基
甲烷化物([Cnmim]TCM,n = 2、4、6 和 8)
离子液体(ILs)的阳离子中烷基链长度对低碳钢(MS)腐蚀性能的影响,系统地研究了它们分别作为结构材料和
二氧化碳捕集设备溶剂的潜在应用。通过扫描电子显微镜、能量色散 X 射线光谱和显微拉曼光谱,在 70 和 80 °C 温度下进行 1 小时到 10 天不等的浸泡测试前后,对 MS 的表面进行了检测。腐蚀从 MS 表面的 MnS 包裹体部位开始,由于 MnS 的溶解而形成空穴,空穴周围可能有含有磁
铁矿(
Fe3O4)和
镁锰铁矿(γ-
Fe2O3)的腐蚀产物。随着阳离子烷基链长度的增加,在包合物位点周围生成的腐蚀产物数量减少,其顺序为[C2mim]TCM > [C4mim]TCM > [C6mim]TCM ≈ [C8mim]TCM。这归因于 ILs 通过吸附在
金属表面并阻断活性位点而产生的缓蚀效果,缓蚀效率随烷基链长的增加而提高。其基本机理与
硫化物夹杂物等 MS 表面活性位点在 IL 中残留的
水和氧存在下的腐蚀过程有关。研究表明,将 IL 中的
水含量提高到约 50 000 ppm 会导致 MnS 内含物溶解更快。最后,研究还证明,从 IL 中去除
氧气可显著降低腐蚀速率。