Imidazole-based ionic liquid as sustainable green inhibitor for corrosion control of steel alloys: A review

Corrosion refers to the degradation of materials caused by exposure of materials to the corrosive environment. The toxicity of some of the synthesised chemical compounds used as inhibitors has initiated the search for eco-friendly inhibitors. Primary goal of this review is to endorse the development of greener corrosion inhibitors and the study of ionic liquids as a viable alternative to chemical inhibitors. Ionic liquids are biodegradable, less volatile, non-inflammable, and less toxic and can be used as inhibitors to protect various metals and alloys from corrosion. Ionic liquids adsorb at the interface of metal and electrolyte. Adsorption of ionic liquids on metals and alloys creates a barrier that prevents corrosion. Ionic liquids are used in a variety of environments to prevent corrosion. This review of imidazolium-based ionic liquids as corrosion inhibitors provides a systematic evaluation of their inhibiting properties against mild steel/carbon steel corrosion. The electrochemical study of different ionic liquids, along with their inhibition efficiencies, are reported in this review. The adsorption of the ionic liquid onto the metal surface was characterised by various techniques such as spectroscopic, surface morphology and theoretical studies. From various reported literature, it is clear that as the increase in the number of hetero atoms, mainly halogens, increases inhibition efficiency of the ionic liquid, inhibition efficiency was also found to increase with the increase in the hydrocarbon chain length. The significant adsorption of the ionic liquid on the metal surface was studied by Monte Carlo simulation and the Molecular dynamics simulation. This review also discusses the scope of research in using imidazolium based ionic liquids as an effective corrosion inhibition of steels.