[BMIM]BF4 ionic liquids as effective inhibitor for carbon steel in alkaline chloride solution

The inhibition action of 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM]BF4) ionic liquids towards carbon steel corrosion in alkaline chloride solution was investigated by electrochemical measurements. The morphology of the surface was examined by atomic force microscopy (AFM), and the surface composition was evaluated via X-ray photoelectron spectroscopy (XPS) as well in order to verify the presence of inhibitor on the carbon steel surface. The results showed that the compound effectively suppressed both cathodic and anodic processes of carbon steel corrosion in alkaline solution by multi-center adsorption on carbon steel surface according to Langmuir adsorption isotherm, and acted as a mixed type inhibitor. The inhibition mechanism was proposed based on the viewpoint of complex physic-chemical interactions between the cationic inhibitor molecule and the carbon steel surface.

Research highlights
► The corrosion inhibition of [BMIM]BF4 for carbon steel in alkaline media was first reported
► The corrosion of carbon steel is effectively reduced by the addition of inhibitor.
► The compound acts as a mixed-type inhibitor and obeys Langmuir adsorption isotherm.
► Inhibitor can block the access of Cl− to metal surface and suppress the localized corrosion.
► The inhibition effect is mainly from the electrostatic interaction with metal surface.