咪唑离子液体对铜在硫酸溶液中的缓蚀作用

采用动电位极化和电化学阻抗谱技术研究了三种新型烷基咪唑离子液体, 1-丁基-3-甲基咪唑硫酸氢盐(BMIM]HSO₄), 1-已基-3-甲基咪唑硫酸氢盐(HMIM]HSO₄), 1-辛基-3-甲基咪唑硫酸氢盐(OMIM]HSO₄), 对铜在0.5 mol·L_-1 H₂SO₄溶液中的缓蚀作用. 实验结果表明: 咪唑离子液体能有效抑制铜在硫酸溶液中的腐蚀, 相同浓度下的缓蚀效率大小顺序为OMIM]HSO₄>HMIM]HSO₄>BMIM]HSO₄. 动电位极化表明三种咪唑化合物的加入对铜的阴阳极腐蚀过程均有抑制作用, 属于混合型缓蚀剂. 电化学阻抗谱用带两个常相位原件的等效电路对含两个时间常数的体系进行拟合, 发现咪唑化合物的添加会引起电荷传递电阻和双电层电容等阻抗参数的变化, 表明此类化合物通过吸附于铜电极与溶液界面起到缓蚀作用, 且这种吸附符合Langmuir吸附等温关系. 吸附过程热力学计算说明咪唑化合物在铜表面发生了自发的物理吸附.

Effect of Alkylimidazolium Ionic Liquids on the Corrosion Inhibition of Copper in Sulfuric Acid Solution

The effects of three newly synthesized alkylimidazolium based ionic liquids: 1-butyl-3-methylimidazolium hydrogen sulfate (BMIMJHSO4), 1-hexyl-3-methylimidazolium hydrogen sulfate (HMIM] HSO4), and 1-octyl-3-methylimidazolium hydrogen sulfate (OMIM]HSO4), on the corrosion inhibition of copper in 0.5 mol·L-1 H2SO4 solution were investigated using potentiodynamic polarization and electrochemical impedance spectroscopy. All the measurements show that these alkylimidazolium ionic liquids are excellent inhibitors for copper in sulfuric acid media and the effectiveness of these inhibitors decreases as follows: OMIM]HSO4>HMIM]HSO4>BMIM]HSO4 at the same concentration. Potentiodynamic polarization studies indicate that the three inhibitors are mixed type inhibitors and that both the cathodic and anodic processes of copper corrosion are suppressed. The electrochemical impedance results were evaluated using an equivalent circuit in which two constant phase elements (CPE) were offered for these systems with two time constants. Changes in impedance parameters (charge transfer resistance and double layer capacitance) with the addition of the inhibitors also suggest that these imidazolium based molecules act by adsorbing at the copper/solution interface. The adsorption of these imidazolium based compounds on the copper surface in an acidic solution is found to fit the Langmuir adsorption isotherm. Thermodynamic calculations reveal that the adsorption of inhibitors on the metal surface occurs by a physisorption-based mechanism involving a spontaneous process.