Study On Corrosion Behavior Of Carbon Steel In CO₂ Containing Ionic Liquid Amine In Aqueous Solution

Large sources of CO2 include large fossil fuel,bioenergy facilities,major CO2 emission industries,and natural gas production.The most common way to capture CO2 in industry is to use monoethanolamine(MEA)solution to absorb CO2,meanwhile it has the problem of easily corroding the equipment.Some types of ionic liquids have negligible volatility,good thermal stability,and large solubility in CO2.Researchers in various countries have begun to study the capture of CO2 in mixed solutions of ionic liquids and alkanolamines.However,there are few literatures on the corrosion of this compound solution,and there is still a lack of research on the corrosion behavior of carbon steel.Accordingly,the study on the corrosion behavior of carbon steel by ionic liquid and alkanolamine mixed solution can provide a reference for the evaluation of the corrosion of this mixed solution.According to the industrial CO2 capture process,it was determined that the basic solution used in the experiment was a mass fraction of 30%MEA+saturated CO2,the experimental steel was 20#carbon steel;Based on the investigation of the effects of various ionic liquids,it was determined that the ionic liquid used in the experiment was 1-butyl-3-methylimidazolium tetrafluoroborate([Bmim]BF4).Also,it was determined a reasonable experimental temperature,experimental pressure,and experimental ionic liquid mass fraction were determined.Using weightlessness test method to test the average corrosion rate of 20#carbon steel in the corrosion system.Furthermore,the corrosion morphology of the experimental coupons was observed by scanning electron microscopy,and the corrosion product elements were detected by EDS.Detecting the ion species in the solution by titration and deducing the possible chemical reactions;Analysis of Electrode Pattern in Tafel Area and Passivation Area by Potentiometric Scanning Method;Using impedance test to fit the equivalent circuit to analyze the electrode surface state;A temperature difference experimental device was designed to study the effect of the addition of ionic liquid[Bmim]BF4 on the temperature differential corrosion of 20#carbon steel.The following conclusions are drawn:(1)With the increase of temperature under the conditions of 30%MEA+saturated CO2 and 30%MEA+saturated CO2+[Bmim]BF4 system,the corrosion process becomes easy.(2)20#carbon steel in the mixed solution containing[Bmim]BF4,the average corrosion rate is lower than that of the solution without ionic liquid.However,the corrosion inhibition effect caused by the increase of ionic liquid mass fraction is not obvious.(3)The addition of[Bmim]BF4 reduces the average corrosion rate of 20#carbon steel but increases the probability of pitting.(4)BF4-ion is the main reason for the increased probability of pitting corrosion.(5)The addition of[Bmim]BF4 in solution results in a decrease in the potential difference between the high and low temperature electrodes.To some extent,it can hinder the forming a thermoelectric cells...