改性咪唑啉类缓蚀剂缓蚀机理的分子模拟

Molecular simulation of imidazoline corrosion inhibition by modification

基于密度泛函理论和分子动力学分别研究了油酸咪唑啉(C17)、季铵化改性咪唑啉(QI)和环氧乙烷改性咪唑啉(EOI)的反应活性、吸附方式、吸附强度和最优吸附构型,揭示了3种缓蚀剂的缓蚀机理.结果表明:3种缓蚀剂分子的反应活性区域主要分布在咪唑环、头基的N原子以及苯环上;3种缓蚀剂分子的缓蚀能力大小为QI>EOI>C17;根据缓蚀剂与金属成键原子态密度可知,咪唑环中N原子的s轨道和p轨道与Cu原子的d轨道发生杂化耦合,形成化学键.本文评价了3种咪唑啉类缓蚀剂的缓蚀性能,明确了咪唑啉类缓蚀剂的缓蚀机理,提供了一种高效的缓蚀剂设计、评价和筛选思路.

In this article, density functional theory and molecular dynamics are used to study the molecular activity and adsorption mechanism of three imidazole molecular corrosion inhibitors including traditional imidazoline oleic acid imidazoline(C17), quaternized modified imidazoline(QI) and ethylene oxide modified imidazoline(EOI). The molecular frontier orbital energy, Fukui index and atomic charge of the three corrosion inhibitor molecules are obtained through DMol3 quantum chemistry calculation, showing that the reactive regions of the three corrosion inhibitor molecules are mainly distributed on the imidazole ring, the N atom of the head group and the benzene ring. The order of the corrosion inhibition performance of three corrosion inhibitor molecules is QI>EOI>C17. Through the calculation of the optimal configuration, we find that the three corrosion inhibitor molecules get attached to the surface of metal mainly relying on the N atoms on the imidazoline ring, and the adsorption strength is consistent with the corrosion inhibition performance of the corrosion inhibitor. According to the density of state of the bond atom between corrosion inhibitors and the surface of metal, s orbital and p orbital of N atom on imidazole ring and d orbital of Cu atom are hybridized and coupled to form chemical bond, i.e., corrosion inhibitor molecules form a film on the surface of metal. Using molecular dynamics simulation, the interaction between corrosion inhibitor molecules and the surface of metal was studied, and the corrosion inhibition performance and mechanism of conventional imidazoline and modified imidazoline were compared. The results show that the corrosion of metal is due to the interaction balance between H2O molecules in the dense layer of water on the surface of metal and the corrosive medium. When there are corrosion inhibitor molecules in the system, the corrosion inhibitor molecules replace part of the H2O molecules in the dense water layer on the surface of metal, i.e., reduce the number of particles for the interaction balance. Therefore, the contact probability between the metal surface and the corrosive medium particles is reduced, and the corrosion gets inhibited. In addition, the existence of corrosion inhibitor reduces the diffusion rate of corrosion particles on the surface of metal and the contact probability between corrosion particles and the metal, thus inhibiting the corrosion of the metal. This work evaluated the corrosion inhibition performance of three imidazoline corrosion inhibitors, clarified their corrosion inhibition mechanism, and provided an efficient way for the design, evaluation and selection of corrosion inhibitors.