Theoretical Study On Structure And Corrosion Inhibition Performance Of Imidazoline Corrosion Inhibitor

Due to their special structure and excellent corrosion inhibition effiency, imidazoline and its derivatives have been extensively used in the field of corrosion and protection of metals. The studies on imidazoline have attracted more attention of researchers. In this thesis,1-(2-thioureaethyl)-imidazoline was used as the basic structure to study the relationship between structures and inhibition efficiencies of of2-alkyl-l-(2-thioureaethyl)-imidazolines,2-aryl-l-(2-thioureaethyl)-imidazolines and undecane-1-(2-thioureaethyl)-imidazolines. The geometry structures, molecular frontier orbits, global parameters and local parameters of31molecules were calculated at the B3LYP/6-311+G*level. Molecular mechanics and molecular dynamic simulation were carried out to study the adsorption of1-(2-thioureaethyl)-imidazolines with different alkyl chain lengths n=11,13,15on the Fe(100) surface. The main conclusions were drawed as following:1. The effects on alkyl groups, aryl groups and hydrophilic groups of imidazolines were studied by density functional theory (DFT). The results shown that the global activitities of six1-(2-thioureaethyl)-2-alkyl-imidazolines with different carbon chain lengths n=9,11,13,15,17,19were distributed on the imidazole ring and the hydrophilic branch. Their local activitities were distributed on the N1and N3atoms of the imidazole ring and the N8、C9、N10and S11atoms of the thioureaethyl groups. Carbon chain length had significant effect on the reaction activity. The global activities of twelve1-(2-thioureaethyl)-2-aryl-imidazolines are different from each other. Their local activitities were distributed on the N1、C2and N3atoms of the imidazole ring and the N8、C9、N10and S11atoms of the thioureaethyl group. Aryl groups have some effect on the active distributions. The global activitities of fourteen imidazoline derivatives(including molecule2) were distributed on the imidazole ring and the hydrophilic branch. Their local activitities were located on the N1and N3atoms of the imidazole ring and the N、C、O and S atoms of the hydrophilic group. The hydrophilic groups showed a certain amount of effects on the active distributions.2. Through the analysis of the relationship between structures and inhibition efficiencies of2-undecyl-l-(2-thioureaethyl)-imdizolines, the model equation I=2441.75-1605.78ΔE+3186η+615-1.14QNI with correlation coefficient0.9938was established. The results can been used to predict efficiencies of inhibitors with similar structures.3. The adsorptions of1-(thioureaethyl)-2-alkyl-imidazolines with different alkyl chain lengths n=11,13,15on the Fe(100) surface were studied by molecular mechanics and molecular dynamics simulation. The cohesive energy of1-(2-thiourea-ethyl)-2-pentadecyl-imidazoline is89.12kJ-mol"1, and its adsorption energy is344.97kJ-mol-1, the solvent energy of1-(2-thioureaethyl)-2-pentadecyl-imidazoline is32.90kJ-mol"1, its adsorption energy in solid decreased to302.23kJ-mol-1, which indicates the adsorption of which on the Fe(100) surface is the most stable.