| Ionic liquids have excellent physical and chemical properties and are widely used in the petrochemical industry,but ionic liquids are corrosive,and the corrosion laws of ionic liquids under different conditions need to be further explored.Therefore,for the typical refineries steels,different ratios of ionic liquids are used as corrosive media to study the corrosion effects of raw material ratio,temperature and water content on different steels.Preliminary investigation of corrosion inhibition methods,screening of high-efficiency corrosion inhibitors to inhibit corrosion,will have important practical significance for the industrial application of ionic liquids.The effects of HCl/CuCl content on the corrosion behavior of five steels(316 stainless steel,304 stainless steel,0Cr13,Q235 and 20#)were studied by weight loss test and polarization curve.It was found that HCl promoted the post-inhibition effect on the corrosion of five steels at n(HCl):n(N-When butylimidazole)=1.1,the corrosion rate is the largest,and the effect of HCl on 304 stainless steel and Q235 steel is greater than that of the other three steels;CuCl promotes the corrosion of five steels;the final determination of corrosion medium ratio is n(HCl):n(N-butylimidazole)=1.1,n(CuCl):n(N-butylimidazole)=1.2.After studying the corrosion properties of five steels in ionic liquids,304 stainless steel and Q235 were selected.The temperature and water content were used to study the electrochemical corrosion of two steels in ionic liquids by weight loss method and electrochemical method.The effect of performance shows that the activity of anion and cation in ionic liquid increases with the increase of temperature,and the corrosion rate of 304 stainless steel and Q235 steel in ionic liquid increases gradually.The corrosion rate of 304 stainless steel increases first and then decreases with the increase of water content.When water content increases from 0%to 20%,the corrosion rate increases from 1.7794 mm/a to 2.7237 mm/a,and then increases to 40%,the corrosion rate decreases to 2.5100 mm/a.The corrosion law of Q235 in different water content ionic liquids is opposite to that of 304 stainless steel.With the increase of water content,the corrosion rate first decreases and then increases.When the water content is 20%,the corrosion rate is the smallest.In addition,sodium tungstate inhibitor is screened out to be the best inhibitor for 304 stainless steel in the ionic liquid with 20%water content(65℃).With the increase of the amount of inhibitor,the corrosion inhibition efficiency gradually increases.When the input is 180 mg/L,the corrosion inhibition efficiency reaches 92.95%,which is a mixed inhibition inhibitor based on cathode inhibition.Sodium borate has the best inhibition effect on Q235 in the ionic liquid corrosion system with 40%water content(65℃),and the inhibition efficiency reaches 90.67%when the input is 120 mg/L.The morphology and composition of corrosion products were characterized by SEM,EDS and XRD.The results showed that the corrosion products of 304 stainless steel in 65℃ionic liquids were irregular blocks and long strips of Cu0.8iNi0.19 and Fe8O8(OH)8Cl1.35,which made the corrosion medium easy to pass through the corrosion product film from the voids,resulting in an increase in the corrosion rate.The corrosion product of Q235 steel in 65℃ionic liquid is Cu,mainly in two forms,one is spherical corrosion product,and the other flower-like corrosion product is formed after the spherical corrosion product continues to grow and rupture.The corrosion products of 304 stainless steel in ionic liquids with 20%water content are uneven in thickness,and the corrosion medium can pass through the corrosion product film from a thin place to make corrosion easier,the corrosion rate increases.The corrosion products are mainly FeN0.0939.The corrosion product of Q235 carbon steel after corrosion with water content of 20%ionic liquid is mainly FeN0.076. |
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