Study on the anodic behavior of AISI E52100 steel in two fluorine-containing ionic liquids

Ionic liquids have a number of excellent applications such as a kind of promising lubricants which have attracted considerable attention. In this work, we investigated corrosion properties which were found in the use of ILs formed by a 1-butyl-3-methylimidazolium cation and a fluorine-containing anion as lubricants of AISI E52100 steel. Electrochemical tests were used to study the anodic behavior of AISI E52100 steel, and surface analysis was performed to study the surface morphology. The electrochemical results showed that increasing temperature accelerates corrosion of the alloy in two kinds of ionic liquids. The data obtained from polarization curves and EIS suggested that the anodic process of the E52100 steel showed generally an active dissolution and increasing temperature can accelerate the corrosion of the steel. At the same time, the main difference as revealed by SEM–EDS plots was that localized corrosion with some irregular etch pits occurred in [Bmim]BF4 ionic liquid; however, a product layer covered uniformly on the surface of metal in [Bmim]PF6. The results of XPS spectrum indicated that the corrosion products formed on the surface of the AISI E52100 steel are mainly composed of FeO, Fe2O3, FeF2 and FeF3.