| Aluminum alloys have been widely used owing to the advantages of low density,high strength,excellent electrical and thermal conductivity,good plasticity and formability,no low-temperature brittleness,easy processing,recycling,energy saving and environmental protection.However,as the intermetallic compounds in aluminum alloys can be used as anodes or cathodes,they are susceptible to local corrosion in natural and operating environments,which will affect the smooth travel of equipment and even lead to catastrophic consequences.Thus,the study on the corrosive protection of aluminum alloy has a great significance for the social and economic development as well as the basic research.Adding corrosion inhibitor into solution is a simple and effective strategy for the corrosion protection of aluminum alloy.With an increase in the awareness of the environmental protection and the national sustainable development strategy,the development of corrosion inhibitor becomes higher and higher,not only being efficient and stable,but also exhibiting the environmental protection.In this regard,using natural amino acids as raw materials to construct a highly corrosion-resistant,multi-functional,green and environmentally friendly corrosion inhibitor can not only achieve efficient protection of aluminum alloys,but also meet the needs of social sustainable development.Meanwhile,inorganic/organic coatings are currently widely used as one of the most effective protective methods for aluminum alloys.The multifunctional amino acid modified corrosion inhibitor is used as an anionic intercalant or functional component to be added into the inorganic/organic film to construct a multifunctional high corrosion resistant film on the surface of aluminum alloy,which is important for expanding the application fields of aluminum alloy materials.Therefore,the main researchful contents and results of this dissertation are as follows:(1)Using L-aspartic acid as raw material,a single guanidine modified amino acid:2-guanidinosuccinic acid(GSA)was prepared.Its structure and purity were characterized by Sakaguchi reaction,nuclear magnetic resonance(NMR),mass spectrometry(LC-MS),and Fourier transform infrared spectroscopy(FT-IR);Through weight loss analysis,potential polarization curve analysis(Tafel)and electrochemical impedance spectroscopy(EIS),this research systematically studied the corrosion inhibition efficiency and corrosion inhibition of 2-guanidinosuccinic acid on aluminum alloy in simulated seawater.At the same time,the bactericidal efficiency of 2-guanidinosuccinic acid was tested by UV-vis spectrophotometer(UV-vis)OD600 value test and colony plate counting method(CFU)of bacterial colony statistics.The research results show that 2-guanidinosuccinic acid,as an anodic corrosion inhibitor,achieves corrosion protection of aluminum alloys by inhibiting the anodic dissolution of aluminum alloys in seawater corrosion media.The corrosion inhibition efficiency is as high as 93.1%.At the same time,due to the guanidine functional group,2-guanidinosuccinic acid can also be used as an efficient fungicide(MIC90 = 60mg/L),and it has broad application prospects as a multifunctional antibacterial corrosion inhibitor.(2)Based on the characteristics of hydrotalcite as a nano-container that it is easily modified by anion modification and has excellent corrosion resistance,2-guanidinosuccinic acid(GSA)was used as an anionic intercalant to prepare a high corrosion resistance,self-repairing,self-antibacterial aluminum alloy surface multifunctional lithium aluminum hydrotalcite conversion coatings(GLDHs).The composition and structure of the hydrotalcite conversion film were analyzed by X-ray diffraction spectroscopy(XRD)and Fourier transform infrared spectroscopy(FT-IR);the surface morphology,film thickness and attachment of the conversion film were tested by scanning electron microscope(SEM).The anti-corrosion ability of the conversion coating was evaluated through electrochemical potential polarization analysis(Tafel)and neutral salt spray test(NSS).Through the scanning electron microscope(SEM)and energy spectrum(EDS),X-ray photoelectron spectroscopy(XPS),Inductively coupled plasma mass spectrometry(ICP-MS)and element analyzer,electrochemical potential polarization(Tafel)and electrochemical impedance spectroscopy(EIS)analysis,scanning vibrating electrode analysis(SVET),we comprehensively studied the self-repairing ability of GLDHs,and discussed the possible mechanism of its self-repair process.Through the UV-vis spectrophotometer(UV-vis)OD600 value test and the colony plate counting method(CFU)of bacterial colony statistical analysis,the self-antibacterial ability of the GLDHs was explored,and the possible mechanism of its self-antibacterial performance was discussed,as well.The research results show that the multifunctional hydrotalcite conversion coatings(GLDHs)have excellent corrosion resistance that can withstand 300 hours of salt spray,the rapid self-repair ability of completing the self-repair process within 28 days,and the ability to maintain more than 95% self-antibacterial efficiency after the self-repair process is completed.In this way,this multi-functional aluminum alloy surface treatment process has broad application fields and development prospects.(3)A series of monoguanidine modified amino acid corrosion inhibitors were prepared using glutamic acid,L-asparagine,glutamine and serine as raw materials.The structure and purity of the product were characterized by Sakaguchi reaction,nuclear magnetic resonance(NMR),mass spectrometry(LC-MS)and Fourier transform infrared spectroscopy(FT-IR).The corrosion inhibition behavior of five amino acid raw materials and five amino acid modified corrosion inhibitors on aluminum alloy was studied by electrochemical impedance spectroscopy(EIS).The anti-bacterial efficiency of each amino acid modified corrosion inhibitor was tested by UV-Vis spectrophotometer(UV-Vis)OD600 value test and colony plate counting method(CFU).Through the calculation of density functional theory,the optimized geometric structure and electronic distribution in the molecular orbitals of five amino acid raw materials and five amino acid modified corrosion inhibitors are obtained.Through global reaction activity analysis and local reaction activity analysis,it is confirmed that the experimental results are highly consistent with theoretical calculations,and combined with the electrochemical experimental results,five amino acid raw materials and five amino acid modified corrosion inhibitors are constructed in aluminum schematic diagram of the adsorption on the surface of the alloy material.(4)With 4-amino-2-((hydrazine methylene)amino)-4-oxobutanoic acid(AOA)as anionic intercalant,and 1H,1H,2H,2H-perfluorooctyltriethoxysilane(PFOTES)as surface modifier,a dual-modified multifunctional lithium aluminum hydrotalcite conversion coating(AFLDHs)on aluminum alloy surface with high corrosion resistance,anti-biofouling and self-antibacterial performance was prepared.The composition and structure of the hydrotalcite conversion coating were analyzed by Fourier transform infrared spectroscopy(FT-IR),X-ray diffraction spectroscopy(XRD),X-ray photoelectron spectroscopy(XPS),energy spectrum(EDS)and Mapping.The surface morphology of the conversion film was characterized by scanning electron microscope(SEM).The corrosion resistance of the conversion coating was evaluated by salt immersion test,neutral salt spray test(NSS),electrochemical impedance spectroscopy(EIS)and Kelvin probe analysis(SKP).Through atomic force microscope(AFM)and water contact angle(CA)tests,the superhydrophobicity and anti-biofouling performance of the conversion film were studied.Through a series of antibacterial experiments,the self-antibacterial ability of the conversion film was studied,and the possible mechanism of its anti-biofouling and self-antibacterial performance was discussed.Experimental results show that dual-modified hydrotalcite conversion coatings(AFLDHs)have high corrosion resistance,high anti-biofouling and excellent self-antibacterial properties.This research combines super-hydrophobic surface modification with anti-bacterial and anti-biofouling functions,and provides a new way to expand the anti-corrosion and multi-functional application of aluminum and aluminum alloys. |
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