腐蚀介质在缓蚀剂膜中扩散行为的分子动力学模拟

采用分子动力学模拟方法,从缓蚀剂膜阻碍腐蚀介质粒子(H2O、H3O+和HCO3-)向金属表面扩散的角度,研究了4种1-R1-2-十一烷基-咪唑啉缓蚀剂(R1:羧甲基(A),羟乙基(B),氨乙基(C),氢(D))抑制碳钢CO2腐蚀的缓蚀机理,并对其缓蚀性能进行了理论评价.腐蚀介质粒子在不同缓蚀剂膜中的扩散系数、粒子与膜的相互作用能以及膜的自扩散性能的计算结果表明:4种缓蚀剂均可形成稳定的缓蚀剂膜,能有效阻碍腐蚀介质粒子向金属表面的扩散,达到抑制或延缓腐蚀的目的;随亲水支链(R1)极性的增加,缓蚀剂膜对腐蚀介质粒子扩散行为的抑制能力逐渐增强;同种缓蚀剂膜对正负离子H3O+和HCO3-比对中性的H2O分子具有更强的扩散抑制能力.综合计算及分析结果,4种缓蚀剂缓蚀性能的理论评价结果为ABCD,与文献实验结果吻合.

Molecular Dynamics Simulation of Corrosive Medium Diffusion in Corrosion Inhibitor Membrane

The corrosion inhibition mechanism of four 1-R1-2-undecyl-imidazoline inhibitors (R1: CH₂COOH (A), CH₂CH₂OH (B), CH₂CH₂NH₂ (C), H (D)) for carbon steel against carbon dioxide corrosion was investigated by molecular dynamics simulation, from the aspect of corrosive medium particle (H₂O, H₃O⁺, and HCO^-₃) diffusion to the metal surface hindered by the corrosion inhibitor membrane. The corrosion inhibition performance of these compounds was also evaluated by the theoretical method. The diffusion coefficients in various corrosion inhibitor membranes, the interaction energies between particles and membranes, and the self-diffusion performance of the membranes indicated that the four imidazoline inhibitors could form stable membranes, which could effectively limited the diffusion of corrosive medium particles to the metal surface, in order to inhibit or delay corrosion. With an increase in the polarity of the hydrophilic chain (R1), the ability of the membrane to hinder particle diffusion enhanced. The membrane was better at limiting the diffusion of charged particles (H₃O⁺ and HCO^-₃) than that of a neutral particle (H₂O). Based on the above analysis, we found that theoretically the corrosion inhibition performance of the four imidazoline inhibitors decreased as follows: A>B>C>D, which agrees with previous experimental results.