直链羧酸型缓蚀剂的缓蚀机理研究

Study on Corrosion Inhibition Mechanism of Linear Carboxylic Acid Corrosion Inhibitor

直链羧酸型缓蚀剂是目前被广泛研究的有机缓蚀剂,羧酸分子中包含亲水的羧基和疏水的烷基链,是典型的表面活性剂型缓蚀剂。本文采用密度泛函理论,在B3LYP/6-31G(d,p)基组下对CH2=CH-(CH2)4COOH(C7)、CH2=CH-(CH2)8-COOH(C11)、油酸和蓖麻油酸四种具有不同碳链长度的直链羧酸型缓蚀剂进行结构优化和量子化学参数计算,进而从理论上研究羧酸缓蚀剂结构与缓蚀性能之间的关系。研究结果表明,缓蚀剂分子中碳链长度的增加会增强缓蚀效率,但对分子的能隙(35)E,硬度η、偶极距μ、化学势u、电子转移数(35)N影响较小。然而,C=C双键的位置对缓蚀剂的缓蚀性能有较大的影响,计算所得的最高占有轨道(HOMO)都分布在C=C双键及其相邻的碳原子,最低空轨道(LUMO)分布在羧基以及相邻的碳原子。通过对四种直链羧酸缓蚀剂的Fukui指数研究发现,四种直链羧酸缓蚀剂的反应活性中心都在C=C双键和-COOH羧基及其附近碳原子。最终得到四种直链羧酸缓释剂的缓蚀效率按照蓖麻油酸>油酸>C11缓蚀剂>C7缓蚀剂的循序逐渐下降。

Straight-chain carboxylic acid type corrosion inhibitors are currently widely studied organic corrosion inhibitors.The carboxylic acid molecule contains a hydrophilic carboxyl group and a hydrophobic alkyl chain.It is a typical surfactant type corrosion inhibitor.In this paper,four linear carboxylic acid corrosion inhibitors with different carbon chain lengths,CH2=CH-(CH2)4COOH(C7),CH2=CH-(CH2)8-COOh(C11),oleic acid and ricinoleic were optimized by using density functional theory under the B3LYP/6-31g(D,P)base group,and the relationship between the structure of carboxylic acid corrosion inhibitors and corrosion inhibition performance was studied theoretically.The research results show that the increase of the carbon chain length in the corrosion inhibitor molecule will enhance the corrosion inhibition efficiency,but has little effect on the molecular energy gap(35)E,hardnessη,dipole distanceμ,chemical potential u,and electron transfer number N.However,the position of the C=C double bond has a greater impact on the corrosion inhibition performance of the corrosion inhibitor.The calculated highest occupied orbitals(HOMO)are all distributed in the C=C double bond and its adjacent carbon atoms,and the lowest space Orbitals(LUMO)are distributed in carboxyl groups and adjacent carbon atoms.Through the Fukui index study of the four linear carboxylic acid corrosion inhibitors,it is found that the reactive centers of the four linear carboxylic acid corrosion inhibitors are all in the C=C double bond and-COOH carboxyl group and its nearby carbon atoms.Finally,the corrosion inhibition efficiency of the four linear carboxylic acid slow-release agents gradually decreased in the order of ricinoleic acid>oleic acid>C11corrosion inhibitor>C7 corrosion inhibitor.