And Their Corrosion Inhibition On The Surface Of Aluminum Alloy

Aluminum alloy has been widely used in civil engineering,transportation and daily life.However,its corrosion has caused serious problems on environment and economy and so on.Therefore,the corrosion inhibition of aluminum alloy is the important topic to be solved in the field of theoretical research and industrial application.At present,the addition of corrosion inhibitors is a most extensive and practical method.Environmentally friendly green surfactants have become focus of the researchers.In this paper,amino acid surfactants were synthesized and their corrosion inhibition properties and mechanism on aluminum alloy in alkaline medium were investigated.Proton nuclear magnetic resonance?¹H NMR?and fourier transform infrared spectrometer?FT-IR?were used to characterize and verify structure of the synthesis matters containing glycine type(C₈H₁₇N?CH₂COONa?₂,C₁₂H₂₅N?CH₂COONa?₂ and C₁₄H₂₉N?CH₂COONa?₂,that was,RNC-n,n=8,12,14),rosin amino acid surfactants(C₂₆H₃₈NNaO₃,that was R-6).Then corrosion inhibition performances of these surfactants for 2024-T3 aluminum alloy in0.01 mol·L^-1 NaOH solution were investigated by static weight loss methods,electrochemical impedance spectroscopy?EIS?,potentiodynamic polarization tests and scanning electron microscopy?SEM?.Finally,the corrosion inhibition mechanism was explored by theoretical calculation of both quantum chemical calculation and molecular dynamics simulation?MD?.The main research contents were as follows:?1?Glycine type surfactants RNC-8 were synthesized by octylamine,sodium chloroacetate and sodium hydroxide.RNC-12 and RNC-14 with different carbon chain length were synthesized.Meanwhile,rosin amino acid surfactant?R-6?was synthesized through the reactions of disproportionated rosin,6-aminocaproic acid,thionyl chloride,4-dimethylamine pyridyl and so on.The results of ¹H NMR and FTIR showed that structures of synthesized surfactants in this experiment were correct,which provided material source for futher study on corrosion inhibition and mechanism of surfactants.?2?Static weight loss method and electrochemical method revealed that four inhibitors had a certain inhibition effect on 2024-T3 aluminum alloy in alkaline condition.The inhibition performance was from strong to weak in order:R-6,RNC-12,RNC-8,RNC-14,whose corresponding corrosion inhibition efficiencies were 92.95%,84.99%,78.28%,74.42%,respectively.SEM indicated the surface of aluminum alloy was smoothest after it was immersed in corrosion solution containing R-6 inhibitor compared with RNC-n?n=8,12,14?.?3?Quantum chemical parameters and MD simulations showed that HOMO-LUMO gap?E and corresponding adsorption energy E_adsorption of R-6 reached minimum compared with the other three surfactants.These results demonstated the abilities with contribution and acceptance electrons of R-6 were the strongest.And it was easy to form adsorption film on the metal surface.Thus,corresponding inhibition efficiency was optimum.In this paper,it has been confirmed that the corrosion inhibition effects of the amino acid surfactants?RNC-n/R-6?on 2024-T3 aluminum alloy were excellent in alkaline medium by experimental and theoretical studies,which not only provides basis for the selection of corrosion inhibitors in the aspect of metal anti-corrosion,but also illustrates the research value and application prospect of surfactant as green corrosion inhibitor.