咪唑啉衍生物对钢在酸中的缓蚀作用与电子密度和前线轨道能量的关系

THE RELATIONSHIP OF CORROSION INHIBITION EFFICIENCY ON STEEL IN ACIDS WITH ELECTRON DENSITY AND THE ENERGY OF FRONTIAL ORBITAL OF IMIDAZOLINE DERIVATIVS

关于二苄基亚砜、硫脲及其它含氮的有机化合物或其混合物对铁在 HF 酸中缓蚀作用已有一些报导。本工作研究含 N、S 或 O 的咪唑啉衍生物对钢(20A,A3,X20)在HF 酸、HCl 酸和柠檬酸中的缓蚀作用。用量子化学的 CNDO/2方法计算了各咪唑衍生物分子中原子的电子密度,同时也计算了前线轨道(HOMO、LUMO)的能量。将计算结果和用失重法测出的腐蚀速度和缓蚀效率进行比较,表明1-氨乙基-2-十一烷基咪唑啉-硫脲缩合物(SM-型化合物)的缓蚀效率最高,是一种性能优良的缓蚀剂。

The inhibition efficiency of imidazoline derivatives containing N,Sor O for steel in hydrofluoric acid,hydrochloric acid and citric acid was studied.The electron density of various atoms and the energy of HOMO, LUMO in the molecules are computed by CNDO/2 method. The experimental results shown that the inhibition efficiency decreases in the following order:2-undecyl-1-(trithioureido)-ethyl-imidazoline (SM-3)>2-undecyl-1-(dithioureido)-ethyl-imidazoline(SM 2)>2- undeeyl-1-(monothioureido)-ethyl-imidazoline(SM-1)>2-undecyl-1- (carboxyethylthioureido)-ethyl-imidazoline(PSM-1)>2-undecyl-1- (carboxyethyl-amino)-ethyl-imidazolne(pAI)>2 undecyl-1-(mul eylamido)-ethyl-imidazo line(MAI)>2-unecyl-1-(aminoethyl)- imidazoline(UAEI). The inhibition efficiency of SM-2 at diffierent concentrations and temperates in 0.166 mol/L citric acid for 20A steel agrees well with Arrhenius formula,i.e.P=A exp(-E/RT),where P is the efficiency of corrosion inhibition and T,the temperature(K).This indicates that the mechanism of corrosion inhibition of SM-type inhibitors is chemical adsorption on the metal surface. The chemical adsorption of SM-type inhibitors on metal surface is explained with computational results by CNDO/2 method.In the mol- ecules of SM-type inhibitors,there are two unsaturated centres:the π-bond on the imidazoline-ring and on the thiourea group.These two centres form feed-back bonds on metal surface with a result of chief donative effect of electron.