Screening Of Hybrid Corrosion Inhibitor For Aluminum Alloy In NaCl Medium And Study On Its Corrosion Inhibition Performance

Aluminum alloys occur obvious pitting corrosion in the medium containing NaCl,which seriously limits its service safety.Adding corrosion inhibitor to the corrosive medium is a simple and feasible protection method.In this paper,multi-scale theoretical calculations which containing quantum chemical（QM）calculation,molecular dynamics（MD）simulation and Monte Carlo（MC）simulation were used to search green corrosion inhibitor with high-efficiency from arginine（Arg）,glutamine（Glu）,and asparagine（Asp）.Then,the selected corrosion inhibitor was compounded with inorganic rare earth corrosion inhibitor.The optimum concentration and corrosion inhibition mechanism of this hybrid corrosion inhibitor were studied by the combination of experimental methods which containing weight loss method,electrochemical test,and microstructure and composition analysis and theoretical calculation method which containing crystal morphology calculation and MC calculation.The main results are as follows:QM results showed the inhibition efficiency was closely related to the distribution of electron orbital and electrostatic potential charge.MC results showed that the adsorption energy in aqueous environment for Arg,Glu,Asp was-209.39 kcal·mol^-1,-69.39 kcal·mol^-1,-66.89 kcal·mol^-1,respectively.Arg had the highest absolute value of adsorption energy,so it had the best blocking effect for corrosive particles.MD results showed that the relative concentration peaks of Cl^-in NaCl solution containing Arg,Glu,Asp molecules were 17.45（?）,18.96（?）,20.06（?）,respectively,and the diffusion coefficients of Cl^-in the corresponding films are 5.18×10^-8 cm²·s^-1,8.01×10^-8cm²·s^-1,1.22×10^-7 cm²·s^-1,respectively.This indicated that among the three molecules,Arg could most effectively reduce the aggregation degree of Cl^-and inhibit its diffusion rate to the aluminum surface.Therefore,the theoretical calculation results showed that the Arg had best corrosion inhibition effect among the three molecules.Weight loss testing results showed that the optimum concentration of the hybrid corrosion inhibitor was 3 mM CeCl₃ with 4 mM Arg,the corresponding inhibition efficiency was 83.78%.Polarization curve results showed the hybrid inhibitor belonged to mixed-type corrosion inhibitor.In the optimal concentration,the pitting potential increased by 208 mV compared with that of 3.5%NaCl solution,which showed the hybrid corrosion inhibitor could significantly improve the pitting corrosion resistance of 5052 aluminum alloy.The electrochemical impedance spectroscopy results indicated the hybrid corrosion inhibitor effectively enhanced the charge transfer resistance of5052 aluminum alloy,which reduced the corrosion rate of 5052 aluminum alloy and inhibited the pitting corrosion.Crystal morphology calculation showed the most stable surface of CeO₂ was{111}surface.MC calculation results showed the CeO₂ film increased adsorption energy of Arg molecules compared with single Al₂O₃ film.Combining the experimental and theoretical results,the inhibition ability of the hybrid inhibitor was attributed to the formation of CeO₂/Al₂O₃-Arg complex films,which dramatically hindered the diffusion of Cl^-and blocked active sites of corrosion reaction.