Inhibition Property And Mechanism Of Imidazole Ionic Liquids For Metals In Hydrochloric Acid Medium

Imidazole ionic liquids are widely applied in many fields such as organic syntheses,catalytic reaction and electrochemistry due to its splendid properties as simle synthetiseing process,stable physical and chemical properties,high conductivity and environment-friendly.However,the corrosion inhibition property of imidazole ionic liquids on metals and alloys has been rarely reported,especially that of 1-hexyl-3-methylimidazolium tetrafluoroborate?[HMIM]BF₄?and 1-hexyl-3-methylimidazolium hydrogen sulfate?[HMIM]HSO₄?used as corrosion inhibitor of 7075 aluminum alloy?AA7075?,70 carbon steel and 304 stainless steel?304 SS?.Thus,[HMIM]BF₄ and [HMIM]HSO₄ have been used as corrosion inhibitors in this thesis,and their corrosion inhibition property and mechanism on 7075 aluminum alloy?AA7075?,70 carbon steel and 304 stainless steel?304 SS?in 1.0 mol·L-1 HCl solution have been studied by weight loss,polarization curve and electrochemical impedance spectroscopy measurements.Following are the main conclusions:Both [HMIM]BF₄ and [HMIM]HSO₄ show a good corrosion inhibition to AA7075,70 carbon steel and 304 SS in 1.0 mol·L-1 HCl solution.Under the same concentration,the inhibition property of [HMIM]HSO₄ is better than that of [HMIM]BF₄.The inhibition efficiency of the two ionic liquids both increase with increasing of inhibitor concentration.The maximum corrosion inhibition efficiency of [HMIM]BF₄ on the three metals and alloys can reach 90.5%?92.7% and 93.3%,while that of [HMIM]HSO₄ can reach 95.1%?94.4% and 96.7%.The potentiodynamic polarization curves demonstrate that the inhibitors act as mixed-type inhibitors to inhibit both anodic metal dissolution process and cathodic hydrogen evolution reactions.The result of the SEM observation has shown that the surface of the metal specimen is smoother after the addition of ionic liquids.This proves good inhibition effects of the two ionic liquids.Based on the calculation and analysis of the standard adsorption gibbs free energy ? Gads and the standard enthalpy ? Hads,and the activation energy Ea of the corrosion process,the adsorption of [HMIM]BF₄ or [HMIM]HSO₄ on AA7075,70 carbon steel and 304 SS surface obeys Langmuir adsorption isotherm and contains a mixture of both physical adsorption and chemical adsorption,but mainly physical adsorption.What's more,the results also show that the respective value of ?Gads and ?Hads of the adsorption of the two ionic liquids on surface of each the three metals are similar,which indicates the adsorption is mainly affected by the cation,the influence of anion is small.By analyzing the mechanism of metal corrosion in hydrochloric acid,considering the molecular structure of [HMIM]BF₄ and [HMIM]HSO₄,the corrosion inhibition mechanism has been studied in this paper and the adsorption structure model has been drawn out.