Study On Synthesis,Inhibition Properties And Mechanism Of Aromatic Quaternary Ammonium Salt Organic Corrosion Inhibitors

Metal corrosion is common trouble during the acidification process,which causes considerable economic losses and waste of manpower and material in the oil and gas industry.At the same time,corrosion will greatly reduce the service life of metal equipment.Among kinds of anti-corrosion techniques,using inhibitors is one of the most economic and effective means for protecting against corrosion in acidification process.Corrosion inhibitors have the advantages of low dosage,simple operation,low cost,remarkable effect and wide adaptability,and have been widely concerned and applied by various industries.However,with the deepening and systematization of corrosion inhibitor research,a large number of traditional corrosion inhibitors have been unable to meet industrial needs due to various defects(high toxicity,poor adaptability and poor adsorption performance).Thus green,functional and efficient corrosion inhibitors are beginning to be favored.Therefore,corrosion inhibitors with simple design and excellent performance are the focus and hotspot of current research.In this paper,five kinds of cationic quaternary ammonium salts with excellent corrosion inhibition performance were prepared by using aromatic rings as raw material.The corrosion inhibition of the prepared inhibitors on Q235 steel surface in 1 mol/L hydrochloric acid solution and its adsorption behavior on Q235 steel surface were studied by means of a series of methods.In this thesis,a series of aromatic cyclic quaternary ammonium salt type corrosion inhibitors were synthesized by using 4,4-bipyridine,4,4’-bis(chloromethyl)-1,1’-biphenyl,alpha’-Dichloro-p-xylene,quinoline,4-chloromethyl styrene and benzyl chloride as raw materials.The corrosion inhibition of the prepared inhibitors on Q235 steel in 1 mol/L hydrochloric acid solution and its adsorption behavior on Q235 steel surface were studied by means of weight loss method,electrochemical technique,surface analysis and quantum chemical calculation.Finally,the adsorption mechanism of the prepared inhibitors was explained.The weight loss experiment results show that the prepared inhibitors are mixed inhibitor that inhibits both cathode and anode,and the inhibition efficiency increases with the increase of inhibitor concentration,and decreases slightly with the increase of temperature.The adsorption of the prepared inhibitors on the carbon steel surface is exothermic,following the Langmuir’s adsorption isotherm,which is a mixed adsorption based on chemical adsorption.The values of ΔSads0 are positive,and change can be ignored at various temperatures,suggesting that the adsorption of the prepared inhibitors is a process of entropy increment.According to the activation energy parameter Ea,after the addition of the prepared inhibitors,the activation energy of the system was significantly increased,which greatly hindered the occurrence of corrosion.The results of electrochemical experiments show that after adding the target corrosion inhibitor,the corrosion current density value icorr is significantly reduced,and the corresponding charge transfer resistance value Rct is significantly increased.The surface topography test results show that the target corrosion inhibitor forms a dense adsorption film on the surface of Q235 steel,which protects the carbon steel from H+corrosion.Quantum chemical calculation results further reveal the corrosion inhibition mechanism and reactive sites of the target corrosion inhibitor on the surface of Q235 steel.In addition,in order to evaluate the applicability and practicability of the prepared inhibitors in actual production,in this paper,the partition coefficients and thermodynamic parameters of two cationic quaternary ammonium salt corrosion inhibitors in oil-water two-phase were also studied,and the effects of different factors on the distribution of corrosion inhibitors in oil-water two-phase were investigated.The results show that the temperature and corrosion inhibitor concentration can promote the distribution ability of corrosion inhibitor in oil-water medium,and the salt concentration and oil-water ratio will hinder the distribution ability of corrosion inhibitor in oil-water medium.