Study On Corrosion Inhibition Performance And Mechanism Of Imidazole Ionic Liquid On 10# Carbon Steel In Acidic Environment

10#carbon steel has excellent properties in terms of plastic toughness and welding performance and is often used in industrial fields.Sulfuric acid and hydrochloric acid are often used as chemical cleaning agents for carbon steel,but acid has serious corrosion hazards to carbon steel（CS）,which not only brings economic losses,but also causes production accidents.The problem of acid corrosion on carbon steel has always been a research hotspot for scientific researchers.In the process of industrial chemical pickling,corrosion inhibitors（CIs）are often added to protect metals.However,traditional corrosion inhibitors are highly toxic and cause serious environmental pollution,which will cause great harm to the environment,ecology and human health.Ionic liquids（ILs）have become potential inhibitors because of their heteroatoms（N,O,S）and heterocyclic structure.In recent years,there have been many research reports on ILs as pickling corrosion inhibitors,but there are very little researches on the differences in the anti-corrosion performance of ILs in different acids and the mechanism of corrosion inhibition is not clear.Therefore,this study first synthesized[C16DMIM][PF₆]ionic liquids,and then targeted at 1M HCl and 1MH₂SO₄ pickling environments.This work has troughed the weight loss method,electrochemical test,scanning electron microscopy（SEM）test,quantum chemistry（QC）and molecular dynamics（MD）.Using simulation method systematically studied the inhibition performance of[C16DMIM][PF₆]on 10#carbon steel.In the end,in order to solve the problem of subpar inhibition performance of ILs in H₂SO₄environment,selecting CH₂O,CH₄N₂S and KI to combined with ILs,and make a thorough inquiry in synergistic corrosion inhibition behavior of 10#carbon steel.The relevant research content and conclusions are as follows:（1）The static weight loss experiment and SEM characterization portray that the ILs can effectively adsorb on the surface of carbon steel.The greater the concentration of[C16DMIM][PF₆]ILs,the lower the corrosion rate of 10#carbon steel,and the higher the protective efficiency of ILs on carbon steel,but ILs has a higher corrosion inhibition efficiency（IE）in HCl solution,which connotes that the effect of CIs in different acids is different,and ILs have a better protection in HCl media for carbon steel than H₂SO₄environment（2）The electrochemical impedance and polarization test results signify that[C16DMIM][PF₆]ILs is a mixed inhibition type corrosion inhibitor.In the two acid solutions,as the concentration of ILs increases,the corrosion current density (I_corr) of carbon steel is significant reduced.On the contrary,the charge transfer resistance (I_corr) on the steel surface increases significantly,which indicates that the corrosion inhibition efficiency of ILs is increasing,and ILs has a significant protective effect on carbon steel.The results of electrochemical test and static weight loss are consistent.It is also found that carbon steel protected by ILs will be more resistant to corrosion in HCl.（3）Quantum chemical（QC）calculations and molecular dynamics（MD）calculations illustrate that ILs corrosion inhibitors mainly interact with the surface of carbon steel through imidazole rings containingπbonds,and the protonated ionic liquids are firmly adsorbed on carbon steel to form a dense layer of protective membrane.（4）The calculation results of adsorption thermodynamics highlight that the adsorption model of ILs in acid systems obey the Langmuir adsorption isotherm.The calculated values of ΔG_ads⁰ are all negative,indicating that the adsorption is spontaneous,and the process is dominated by physical and chemical adsorption.（5）The results of the research on the properties of compound corrosion inhibitors（CIs）through a series of methods such as weight loss and electrochemical tests.It describes that all three compound agents have a synergistic effect with ILs inhibitors,and the order of the synergistic effect is KI>CH₄N₂S>CH₂O.Quantum chemistry calculation results are consistent with experimental results,confirming that the corrosion inhibition effect is related to the molecular energy band（Δ）.The smaller theΔ,the stronger the interaction between the compound corrosion inhibitor and the carbon steel,and the better the corrosion inhibition effect.