Study On The Corrosion Inhibition Performance Of Mango Gum Graft Copolymer On J55 Carbon Steel In CO₂ Environmen

In this paper,mango gum graft copolymer was selected as the inhibitor,and the inhibitor was prepared by graft copolymerization of acrylamide,vinyl acetate and caprolactam with mango gum by chemical synthesis.The composition of the graft copolymer was characterized by nuclear magnetic resonance spectroscopy,Fourier transform infrared absorption spectroscopy and gel permeation chromatography,to identify whether the synthesis was successful.The corrosion inhibition of J55 carbon steel in 3.5%NaCl saturated CO2 solution was evaluated by static weight loss method,electrochemical impedance spectroscopy,potentiodynamic polarization curve,scanning electrochemical microscope and atomic force microscope,and the effect of mangifera grafted with different monomers on the corrosion inhibition of J55 carbon steel was compared.Finally,the inhibition mechanism of different mangiferin graft copolymer inhibitors was analyzed by thermodynamics,kinetics calculation and molecular dynamics simulation.The experimental results show that:(1)From infrared spectrum,nuclear magnetic resonance spectrum and gel permeation chromatography,it can be seen that the molecular weight distribution of the three graft copolymers is relatively narrow,and contains more C=O,C-O,C-N,N-H and other groups with lone pair electrons,which can provide electrons to the empty orbits of Fe,thus adsorbing on the surface of J55 carbon steel to form an adsorption film,so as to achieve the purpose of inhibiting corrosion.(2)The results of static weight loss test show that the inhibition efficiency of the copolymer inhibitor decreases with the increase of temperature and increases with the increase of concentration.When the temperature is 30℃ and the concentration is 400mg/L,the inhibition efficiency of the copolymer of three different monomers(acrylamide,vinyl acetate and caprolactam)grafted mango gum can reach 92.87%,90.66%and 87.20%.(3)It can be seen from the impedance spectrum and polarization curve that the inhibitor of mango gum graft polymer with different monomers is a kind of mixed inhibitor,their inhibition efficiency is different according to the grafting monomers,and the order of the difference is:acrylamide>vinyl acetate>caprolactam.The inhibition efficiency of mango gum copolymer with acrylamide as graft monomer is the best,and the inhibition efficiency is 80.94%and 78.50%respectively when the concentration is 100mg/L at room temperature,measured by electrochemical impedance spectroscopy and polarization curve.(4)The results of thermodynamics and kinetics show that their adsorption is a thermodynamic spontaneous process and exothermic process,which follows the Langmuir isotherm adsorption model and is mainly physical adsorption with a small amount of chemical adsorption.The reason for the difference of the corrosion inhibition performance of the graft copolymers of three different monomers is that the reaction activity of the three graft monomers is different,which leads to the difference of the grafting rate.Among them,there is a π-π conjugated system of acrylamide,and the amino group belongs to the electron absorption group,which reduces the density of double bond electron cloud,and is easy to be triggered by peroxide to produce active radicals,so it has higher reaction activity,more It is easy to graft with the hydroxyl group on the mango gum,which improves the grafting rate.(5)Mangiferin grafted copolymers with three different monomers can replace water molecules to adsorb on the Fe(110)surface in a parallel manner,which is the most stable adsorption mode,which is conducive to the adsorption of polymer molecules and metals through electrostatic stress or the formation of coordination bonds,and finally to the formation of a high coverage adsorption membrane.