Synthesis And Corrosion Inhibition Of A New Imidazoline Corrosion Inhibitor

Metal corrosion is becoming a serious question which has seriously affected the production and life of human beings.However,using of corrosion inhibitors can effectively decrease the rate of metal corrosion.Imidazoline inhibitor is an excellent corrosion inhibitor with the advantage of friendly to environment,easily to prepare and high efficiency at low concentration.In this paper,three kinds of bis-imidazoline intermediates were synthesized and then reacted with benzyl chloride to obtain the corresponding bis-imidazoline inhibitors,including PIM-2-IMP,PIM-4-IMP and PIM-8-IMP.The products were analyzed by FT-IR,UV-Vis,NMR and elemental analysis.The effects of different reaction conditions on the yield of products were studied by orthogonal experiments,and the optimum synthesis conditions were determined.The corrosion inhibition properties of the three kinds of bis-imidazoline compounds on N80 steel in 15%HCl solution were studied by static weight loss method and electrochemical method.In addition,the adsorption modes of three kinds of corrosion inhibitors on the surface of N80 steel were studied,respectively.Finally,three kinds of bis-imidazoline intermediates were calculated with density functional theory?DFT?by quantum chemistry method.The experimental results show that the reaction time of both amidation and cyclization are4 hours.And the amidation temperature were 170?,180?and 190?,while the cyclization temperature were 190?,220?and 240?,respectively,corresponding to the increasing number of carbon atoms in the chain.The corrosion experimental results show that all the three kinds of bis-imidazoline corrosion inhibitors have good corrosion inhibition performance for N80 steel in HCl solutions.The inhibition efficiency increases with the number of carbon atoms increasing in the chain.At the fixed temperature,the inhibition effect was enhanced with increasing of the concentration of corrosion inhibitor.Interestingly,the inhibition efficiency can achieve to 98%in 15%HCl solutions using 6 mmol/L PIM-8-IMP.According to the results of experiments,the adsorption of three kinds of corrosion inhibitors are in accord with the Langmuir isotherm adsorption model,and the physical adsorption and chemical adsorption occur simultaneously on the metal surface.According to electrochemical test results,three imidazoline inhibitors belong to mixed inhibitor.Quantum chemical parameters such as the lowest unoccupied molecular orbital energy(E_LUMO),the highest occupied orbital energy(E_HOMO),the global hardness???and the energy gap??E?etc.were calculated using DFT at B3LYP/6-3111++G level.The relationship between the inhibitive performance and quantum chemical parameters were investigated.And the results showed that the inhibition efficiency is getting higher with increasing of ELUMO,as well as?E and?,based on the structure-activity relationship.