Study On Synthesis,Corrosion Inhibition And Mechanism Of Imidazoline Derivatives

Adding corrosion inhibitor is one of the most economical and effective way in many methods of corrosion prevention.Corrosion inhibitors are widely used in industrial processes such as pickling and acidification of oil wells,which can effectively slow down the corrosion of pipelines and equipment by media.Many studies have shown that the most widely used organic corrosion inhibitors generally contain N,O,S and other heteroatoms,which usually exist in imidazole ring,quinoline and other heterocyclic ring.In addition,the organic corrosion inhibitor with special unsaturated ? bond also has good corrosion inhibition effect.Imidazoline corrosion inhibitors are widely used in industry due to the presence of N heterocyclic and unsaturated bonds in their structure,and their preparation is simple,green and efficient.However,due to the poor water solubility,they can't be well dispersed or dissolved in water-borne corrosive media,so their corrosion inhibition performance are also limited.Therefore,the modification of imidazoline to improve its hydrophilicity is one of the key points of the study.In this paper,based on the study of imidazoline oleate corrosion inhibitor(IMO-1,IMO-2),in order to improve their poor dissolution effect,a series of imidazoline derivatives were synthesized.It includes three kinds of corrosion inhibitor,such as bisebutenyl gemini imidazoline corrosion inhibitor(DBIA),polyetheryl gemini imidazoline corrosion inhibitor(PGI)and two kinds of triazinyl gemini imidazoline corrosion inhibitor(IPT-1,IPT-2).The 1HNMR and IR had been used to characterize the structure of the several kinds of corrosion inhibitors,and through the weight lose experiment testing the corrosion rate of these corrosion inhibitors.Then,further tests were carried out with electrochemical experiments,such as chemical impedance and polarization curve.In addition,the activation energy and adsorption method of the corrosion process were analyzed by contact angle measurement,adsorption thermodynamics,kinetic,and isotherm adsorption curve fitting.Finally,combining with quantum chemistry calculation,the mechanism model of adsorption and inhibition of corrosion inhibitor are proposed.The results showed that the solubility of these corrosion inhibitors was improved to different degrees compared with IMO-1 and IMO-2.The results of weight lose experiment show that several imidazoline inhibitors have good corrosion inhibition effect,among which DBIA has the best corrosion inhibition effect,followed by PGI and IPT-2.Therefore,the method of quaternization and the introduction of polyether chain structure can not only increase the dispersity of imidazoline,but also ensure that the corrosion inhibition rate of imidazoline does not decrease.The results of electrochemical analysis showed that the modified corrosion inhibitor molecules bonded to the surface of Q235 steel through various interactions such as imidazoline ring,triazine ring and polyether chain after dissolution and dispersion,which established a tight barrier on the interface and hindered the corrosion behavior.These corrosion inhibitors are all anodic corrosion inhibitors for inhibiting the anode,and they can form monolayer adsorption on the surface of Q235 steel.The adsorption process is mainly chemisorption,spontaneous exothermic process and accompanied by entropy increase.The quantum chemical calculation shows that the modified corrosion inhibitor has multiple active sites in the molecular structure,which can form coordination bonds with the empty Fe orbitals in Q235 steel,thus resulting in stable adsorption.The contact angle test results show that the designed corrosion inhibitor can enhance the hydrophobic property of Q235 steel surface,and the surface morphology test shows that several corrosion inhibitors can play an effective role in alleviating the corrosion of Q235 steel,and make the surface of the metal sample is smooth and bright as before.To sum up,in order to improve the solubility of imidazoline oleate corrosion inhibitor in aqueous medium,water soluble groups can be introduced into its molecules,such as polyethyl chain,quaternary ammonium group,triazine ring,hydroxyl group,etc.As well as the structural design refer to geminic surfactants also can improve the effect.The structure of the imidazoline derivatives formed after the design optimization,not only its dissolution effect has been effectively improved,but also can maintain the excellent corrosion inhibition performance of the imidazoline corrosion inhibitor,it provides a good idea for the design of corrosion inhibitor molecules.