Synthesis And Corrosion Inhibition Properties Of Amino Acid Schiff Base Of Magnesium Alloy Inhibitor

Metal corrosion is a global problem,showing an adverse effect on the economic growth of both developed and developing countries adversely.A great deal of metal-containing materials are wasted due to the corrosion,which results in huge economic losses and personal safety worldwide.Therefore,there is an extensive attention on corrosion in academia and industry.In recent years,magnesium and its alloys have received wide attention because of their good properties,such as low density,high specific strength,good electrical conductivity,and other excellent properties.Magnesium alloy materials have a wide range of applications in aerospace,military industry,automotive industry,electronics and other industries.However,owing to the poor corrosion resistance of magnesium and its alloys,their applications are limited tremendously in many fields.Therefore,it is necessary to study the anticorrosion methods of magnesium and its alloys.Corrosion inhibitor technology,is one of the practical methods for protecting metals from corrosion in a corrosive environment,due to its low cost,easy operation,and good effect.Corrosion inhibitors have been successfully applied to the protection of various metal materials,such as carbon steel,aluminum alloy,and copper.But there are relatively few studies on corrosion inhibitors for magnesium and its alloys.In addition,the environmental friendliness of corrosion inhibitors is also considered.It is of great value and significance to find a kind of novel and eco-friendly corrosion inhibitors for the application and development of magnesium alloys.In this paper,a class of amino acid Schiff base organic corrosion inhibitors were synthesized through experimental methods,and their corrosion inhibition effects on magnesium alloys were studied.Specific research is as follows:Firstly,eight kinds of novel amino acid Schiff bases were prepared by the condensation reaction of Aryl-pyrazolealdehyde with glycine,?-alanine,L-histidine and L-phenylalanine,respectively,which are referred to as AMSB-1,AMSB-2,AMSB-3,AMSB-4,AMSB-5,AMSB-6,AMSB-7 and AMSB-8,respectively.Elemental analysis,nuclear magnetic resonance,infrared spectroscopy,and mass spectrometry were used to characterize the structure of eight amino acid Schiff bases.Secondly,the corrosion resistance of eight kinds of amino acid Schiff bases on AZ31B magnesium alloy in 0.05 wt.%NaCl solution was investigated by AC impedance spectroscopy anddynamic potential polarization test methods.The electrochemical results show that all amino acid Schiff bases have good corrosion inhibition efficiencies of more than 80%,all of which are the mixed corrosion inhibitors,inhibiting the reaction of cathode and anode.Then,the influence of sodium(E)-3-((1-(4-fluorophenyl)-5-hydroxy-3-methyl-lH-pyrazol-4-yl)methyleneamino)propanoate(AMSB-6)concentration on the corrosion inhibition performance was discussed through AC impedance spectroscopy and dynamic potential polarization test methods.It is found that the optimal concentration is 5 g/L and the corrosion inhibition efficiency reaches 96.7%.The adsorption model analysis shows that the adsorption of AMSB-6 conforms to the Langmuir adsorption isotherm,and the corresponding ?G0ads is-28.87 kJ·mol-1,which indicates that the adsorption process of AMSB-6 is a physicochemical mixed adsorption process Scanning electron microscopy results show that the corrosion inhibitor is adsorbed on the surface of magnesium alloy.Compared with the blank sample,the corrosion marks are reduced significantly.The results of atomic force microscopy reveal that the roughness of the sample treated with corrosion inhibitor is also decreased remarkably.The methods of energy spectrum analysis and X-ray powder diffraction prove that AMSB-6 forms a protective film by adsorbing on the surface of AZ31B magnesium alloy to inhibit its corrosion.Finally,the corrosion inhibition effect of AMSB-6 on the AZ31B magnesium alloy in the atmospheric environment simulation fluid was explored.The electrochemical method was used to study the inhibitory effect of AMSB-6 concentration and temperature on the AZ31B magnesium alloy.The results of electrochemical experiments showed that with the increase of AMSB-6 concentration,the corrosion inhibition efficiency gradually increases,and the highest corrosion inhibition efficiency reches 81.3%at a concentration of 20 mmol/L.But as the temperature increases,the efficiency of the corrosion inhibitor gradually decreases.The corrosion inhibitor efficiency drops to 39.1%at 50?.The results of polarization curves and adsorption isotherms indicate that AMSB-6 is an anode-type corrosion inhibitor with Langmuir adsorption behavior in the atmospheric environment simulation fluid,and the main adsorption method is physicochemical adsorption.Scanning electron microscope and energy spectrum analysis prove that AMSB-6 has a good corrosion inhibition effect on AZ31B magnesium alloy.The structure of corrosion products was analyzed by X-ray powder diffraction method,and a possible corrosion inhibition mechanism was proposed.AMSB-6 is combined with magnesium through physical and chemical adsorption to form a protective film that prevents the corrosion of corrosive ions on the magnesium alloy and reduces the corrosion of the magnesium alloy.This shows that the amino acid Schiff base AMSB-6 is a potentially valuable magnesium alloy corrosion inhibitor.