| Mg is one of the most abundant elements in the crust and the lightest structural metal material Mg and Mg alloy have the advantages of high specific strength,specific stiffness,good thermal conductivity,good electromagnetic shielding,damping,shock absorption,machinability,low processing cost and easy recovery,which are indispensable materials for human economic and social development and people's production and life.However,Mg and its alloys are prone to corrosion in the environment due to their high chemical activity,low electrode potential and poor chemical stability.Although there are many corrosion protection methods for Mg alloys,the technology of adding corrosion inhibitors is a simple,practical,cost-effective and widely applicable method for Mg and its alloys.Today,people's awareness of environmental protection is becoming stronger and stronger.Therefore,it is one of the hot spots to find green and efficient corrosion inhibitors for Mg alloy.Ionic liquids(ILs)have the advantages of non-volatile non combustible,strong conductivity,high viscosity at room temperature,large heat capacity,low vapor pressure,stable properties and environmental friendliness.As a green and environmentally friendly corrosion inhibitor for Mg alloy,it has attracted extensive attentionIn this paper,three kinds of quaternary ammonium ionic liquids([N 8,8,8,,2][NTf2],[N8,8,8,14][NTf2]and[N8,8,8,Bn][NTf2])were synthesized.The inhibition effects of three quaternary ammonium ionic liquids on AZ31B Mg alloy in 0.05 wt.%NaCl solution(simulated marine atmosphere)were studied by electrochemical impedance,potentiodynamic polarization curve,adsorption model,surface analysis and theoretical calculation.The main research work and results are as follows:1.Two kinds of quaternary ammonium ionic liquids[N8,8,8,12][NTf2]and[N8,8,8,14][NTf2]with different chain lengths were synthesized and their corrosion inhibition effect on AZ31B Mg alloy in 0.05 wt.%NaCl solution was studied.The results showed that[N8 8,8,12][NTf2]and[N8,8,8,14][NTf2]ionic liquids had a certain protective effect on AZ31B Mg alloy in 0.05 wt.%NaCl solution,and the corrosion inhibition efficiency increased with the increase of the corrosion inhibitor concentration.When the corrosion inhibitor concentration was 10 ppm,the corrosion inhibition efficiency reached the highest,but when the corrosion inhibitor concentration continued to increase,the corrosion inhibitor efficiency decreased instead,the corrosion inhibition efficiency of the corrosion inhibitor would not always increase with the increase of the corrosion inhibitor concentration.When the concentration of inhibitor[N8,8,8,12][NTf2]was 10 ppm,the inhibition efficiency was 83%,when the concentration of inhibitor[N8,8,8,14][NTf2]was 10 ppm,the inhibition efficiency was 90%.By comparing the inhibition efficiency of the two inhibitors,it could be seen that[N8,8,8,14][NTf2]ionic liquid with longer chain length had better corrosion inhibition effect.At the same time,the potentiodynamic polarization curves showed that[N8,8,8,12][NTf2]and[N8,8,8,14][NTf2]were cathodic corrosion inhibitors.The Langmuir isotherms showed that the adsorption of[N8,8,8,12][NTf2]and[N8,8,8,14][NTf2]ionic liquids on AZ31B Mg alloy surface was mainly physical adsorption.The results of surface analysis and theoretical calculation also showed that[N8,8,8,14][NTf2]had better corrosion inhibition effect on AZ31B Mg alloy in 0.05 wt.%NaCl solution2.Ionic liquid[N8,8,8,Bn][NTf2]was synthesized and its corrosion inhibition effect on AZ31B Mg alloy in 0.05 wt.%NaCl solution was studied by electrochemical experiment,adsorption model,surface analysis and theoretical calculation.The results showed that the inhibition efficiency of[N8,8,8,Bn][NTf2]for AZ31B Mg alloy in 0.05 wt.%NaCl solution increased with the increase of[N8,8,8,Bn][NTf2]concentration,and the maximum inhibition efficiency was 91.6%when the concentration of[N8,8,8,Bn][NTf2]was 50 ppm In addition,the results of the potentiodynamic polarization curve proved that[N8,8,8,Bn][NTf2]belonged to the cathode type corrosion inhibitor.The adsorption of[N8,8,8,Bn][NTf2]on the surface of AZ31B Mg alloy was mainly physical adsorption,and it conformed to the Langmuir adsorption mode3.The corrosion inhibition of AZ31B Mg alloy immersed in 50 ppm[N8,8,8,Bn][NTf2]diluted with absolute ethanol for different times in 0.05 wt.%NaCl solution was also studied by electrochemical and surface analysis methods.The results showed that the longer the immersion time,the higher the corrosion inhibition efficiency.When the immersion time increases from 96 h to 192 h,the inhibition efficiency decreased slightly,and the maximum inhibition efficiency was 91.5%. |
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