醇胺与羧酸阻锈剂分子的构效评估与机理分析

Evaluation and Mechanism Analysis of the Molecular-structure-property Relationship of Alcoholamine and Carboxylic Rebar Corrosion Inhibitors

钢筋阻锈剂是一种高性价比的钢筋防腐材料,在桥梁钢筋混凝土结构中应用广泛。有机阻锈剂的阻锈效率主要取决于其分子结构,然而受仪器设备分辨率所限,目前的相关研究多集中于宏观尺度的电化学响应分析,较少涉及微纳尺度的阻锈机理分析。因此,基于分子动力学技术,分别建立了阻锈剂与钢筋钝化膜的纳观尺度模型,模拟了醇胺类、羧酸类阻锈剂分子与钢筋钝化膜间的界面交互作用,揭示了原子尺度上的阻锈机理。基于阻锈剂-钝化膜分子动力学模型对其阻锈响应规律进行分析,确定2种有机分子均可有效阻碍氯离子在钢筋钝化膜表面的吸附和点蚀,其中羧酸类阻锈剂的阻锈效率更佳(75.8%)。通过深入探究2种阻锈剂与钢筋钝化膜基体吸附差异,研究发现:高极性的羧基官能团可与钢筋钝化膜表面的羟基发生强烈的静电吸引作用,使得羧酸类分子稳定地吸附在钝化膜表面,氯离子的吸附位点被大量占据,因而阻锈效率较高;而醇胺类分子由于官能团极性较弱,在界面上的吸附作用不显著;同时,分子模拟证明,阻锈剂中的极性官能团还能直接吸引氯离子,这一机制同样抑制了氯离子在钢筋表面的吸附和破坏;此外,电化学试验的结果与分子模拟一致,这表明分子模拟技术可在有机阻锈剂的分子设计与评估中发挥重要作用,继而为钢筋混凝土结构的耐久性设计提供科学依据与技术手段。

Rebar corrosion inhibitors are a high-cost performance rebar anti-corrosion technology that is widely used in bridge reinforced-concrete structures.The inhibiting efficiency of organic corrosion inhibitors mainly depends on the molecular structure of organic materials.However,the current related research mostly focuses on the macroscale electrochemical response analysis and less on the micro-nanoscale corrosion-inhibition mechanism analysis because of the resolution limitations of equipment.Therefore,in this work,based on molecular dynamics,nanoscale models of corrosion inhibitors and reinforcing-steel passivation films were established,the interactions at the interface between alcohol amine/carboxylic acid corrosion-inhibitor molecules and reinforcing-steel passivation film were simulated,and the corrosion-inhibiting mechanism at the atomic scale was revealed.According to the corrosion-inhibiting response analysis of the corrosion inhibitor-passivation film molecular-dynamic model,both organic molecules are considered to effectively hinder the adsorption and pitting of chloride ions on the surface of the steel passivation film in which the carboxylic acid corrosion-inhibitor efficiency is better(75.8%).In addition,by comparing the adsorption difference between the two corrosion inhibitors and reinforcing steel passivation-film matrix,the highly polar carboxyl functional groups is found to have a stronger electrostatic attraction with the hydroxyl groups at the surface of the reinforcing-steel passivation film,which leads to a more stable interfacial adsorption.Consequently,the chloride-ion adsorption sites are heavily occupied,which contributes to a higher corrosion-inhibiting efficiency.In contrast,the alcohol amine molecules do not exhibit significant adsorption at the interface because of the weak polarity of the functional group.Furthermore,the molecular simulations prove that the polar functional groups in the organic materials can directly attract chloride ions,and this mechanism inhibits adsorption and destruction of chloride ions at the surface of the rebar.Finally,electrochemical tests were performed,and the results agree with the molecular-simulation results.These results indicate that the molecular-simulation techniques can play an important role in the molecular design and evaluation of organic corrosion inhibitors and provides a scientific basis and technical means for the design of the durability of reinforced-concrete structures.