咪唑啉与其中间产物酰胺缓蚀性能的比较

使用油酸和二乙烯三胺在不同温度下合成了油酸基酰胺（A1）、油酸基咪唑啉（AM）以及既含有酰胺又含有咪唑啉（A2）的3种缓蚀剂。采用电化学阻抗谱（EIS）和极化曲线对3种合成产物在CO₂饱和的质量分数3.5%的NaCl溶液中进行缓蚀性能评价。EIS和极化曲线结果表明：A1、A2和AM均能对Q235钢在该介质中的腐蚀起到显著的抑制作用；3种合成产物的缓蚀效率由高到低为AM > A2 > A1，说明咪唑啉的缓蚀效果比酰胺的好。通过量子化学的方法研究了咪唑啉分子和酰胺分子的缓蚀机理，理论计算结果表明：与酰胺分子相比，咪唑啉分子的成键能力更强，从而更容易吸引电子，与Fe基体更容易发生相互作用。通过Hirshfeld计算了咪唑啉和酰胺分子中原子的Fukui指数并分析了其反应活性位点，Fukui指数的分析结果与分子前线轨道HOMO和LUMO的分析结果一致。

Comparison of the corrosion inhibition performance of imidazoline and its intermediate amide

Three kinds of corrosion inhibitors A1, A2 and AM were synthesized by a step-heating method. Three-stage step heating of a mixture of oleic acid and diethylenetriamine in the molar ratio of 1:1.2 successively afforded an oleic acid amide (A1), which on further heating underwent cyclization to form a mixture (denoted A2) of an imidazoline and unreacted A1, followed by-at the highest temperature-complete conversion to the imidazoline (denoted AM). The products were characterized by infrared spectroscopy. Electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization curves methods were used to evaluate the corrosion inhibition performance of A1, A2 and AM in a 3.5% (mass concentration) NaCl solution saturated with carbon dioxide. EIS and potentiodynamic polarization curves showed that A1, A2 and AM can all significantly inhibit the corrosion of Q235 steel under these conditions. The corrosion inhibition efficiency was found to decrease in the order AM > A2 > A1, indicating that the imidazoline has better corrosion inhibition than the amide. The mechanism of corrosion inhibition of imidazoline molecules and amide molecules was studied theoretically by quantum chemistry calculations. The calculations showed that the imidazoline molecules have stronger bonding ability, stronger electron attracting ability, and a stronger interaction with Fe matrix than the amide molecules. The Fukui index of atoms in imidazoline and amide molecules was calculated by the Hirshfeld method and the reactive sites in imidazoline and amide molecules were analyzed. The results of the Fukui index analysis were consistent with the results of the molecular frontier orbital HOMO and LUMO analysis.