十八胺在碳钢表面吸附和成膜的分子动力学研究

Study on Molecular Dynamics of the Adsorption and Film Formation of Octadecylamine on Carbon Steel Surface

华龙一号机组主给水系统大量使用P280GH碳钢管道,并应用十八胺(ODA)在管道内壁吸附形成缓蚀膜,ODA可高效抑制腐蚀,避免管道失效和蒸汽发生器(SG)严重结垢。但ODA在碳钢表面的吸附和成膜机理目前仍不明确,严重制约了ODA的性能优化和推广应用,针对该问题,采用分子动力学(MD)模拟开展研究。结果表明,ODA分子头部的氮原子与碳钢表面铁原子形成配位键,促使ODA分子吸附“锚定”。所形成缓蚀膜的微观构型与ODA浓度相关。浓度较低时,缓蚀膜呈ODA分子尾链间交织较差的单层构型,随着浓度增加,缓蚀膜逐渐演变为ODA分子尾链间紧密交织的复杂双层构型。在ODA浓度超过一定阈值后,缓蚀膜的构型不再显著变化,未吸附成膜的ODA分子最终积聚形成胶体微团。

P280GH carbon steel pipe is widely used in the main feedwater system of Hualong One unit,and octadecylamine(ODA)is applied to form a corrosion inhibition film by adsorption on the inner wall of the pipe.ODA can effectively inhibit corrosion and avoid pipe failure and serious scaling of steam generator(SG).However,the mechanism of adsorption and film formation of ODA on carbon steel surface is still unclear,which seriously restricts the performance optimization,optimization and application of ODA.In order to solve this problem,molecular dynamics(MD)simulation method is used to carry out the study.The results show that the nitrogen atoms at the head of the ODA molecule form coordination bonds with the iron atoms on the carbon steel surface,which promotes the adsorption and anchoring of the ODA molecule.The microscopic configuration of the corrosion inhibition film formed is dependent on the concentration of ODA.At low concentration,the corrosion inhibition film has a poorly interwoven single-layer configuration between ODA molecular tail chains,and as the concentration increases,the corrosion inhibition film evolves into a tightly interwoven complex bilayer configuration between ODA molecular tail chains.After the concentration of ODA exceeds a certain threshold,the configuration of the corrosion inhibition film no longer changes significantly,and the ODA molecules that are not adsorbed to form the film eventually accumulate to form colloidal micelles.