咪唑啉缓蚀剂膜抑制腐蚀介质扩散行为的MD研究

采用分子动力学模拟的方法,对5种1-(2-氨乙基)-2-烷基-咪唑啉缓蚀剂[(NH2)C2H4-C3H4N2-CH2(CH2)nCH3,n=5,7,9,11,13]抑制CO2腐蚀的缓蚀机理进行了研究.计算了4种腐蚀介质粒子(H2O,H3O+,Cl-和HCO-3)在不同缓蚀剂膜中的扩散系数,并从自由体积分数、腐蚀介质粒子与缓蚀剂膜的相互作用、膜的自扩散性能等方面对缓蚀剂膜抑制腐蚀介质粒子扩散行为的微观机理进行了分析.扩散系数的计算结果表明:缓蚀剂膜能有效抑制腐蚀介质的迁移,削弱其腐蚀能力;与中性H2O分子对比,缓蚀剂膜对H3O+,Cl-和HCO-3带电离子的扩散具有更强的抑制效果;随烷基链长的增加,5种缓蚀剂膜对腐蚀粒子扩散的抑制能力呈增强趋势.综合分子动力学计算结果,5种缓蚀剂缓蚀性能随着烷基链长的增加逐渐增强,理论评价结论与实验结论相吻合.

MD Study of Imidazoline Corrosion Inhibition Membranes Restrain Corrosive Medium Diffusion Behaviors

The inhibition mechanism of five 1-(2-aminoethyl)-2-alkyl-imidazoline compounds [(NH2)C2H4-C3H4N2-CH2(CH2)nCH3, n=5, 7, 9, 11,13] against CO2 corrosion was investigated by molecular dynamics simulation method. Diffusion coefficient of four corrosive medium particles (H2O, H3O+, Cl- and HCO -3 ) in inhibitor membranes was calculated and the diffusion mechanism was studied by analyzing free volume fractional, interaction energy and self-diffusion coefficient of membranes. Results of diffusion coefficient showed that the membranes could restrict the diffusion of corrosive medium particles effectively so as to slow down the corrosion processes, and the diffusion of H3O+, Cl- and HCO -3 was hindered more strongly than that of H2O. As the alkyl chain length increased, the ability of the membrane to hinder the diffusion of particles enhanced. With the help of the theoretical results, the inhibitor had preferable inhibition performance with the increase of alkyl chain length, which accorded well with experimental results.