Adsorption and inhibition behavior of imidazolium tetrafluoroborate derivatives as green corrosion inhibitors for carbon steel.

The adsorption and inhibition mechanism of chain length increase and group substitution of imidazole tetrafluoroborate derivatives for the corrosion inhibition of carbon steel in HCl solution was revealed in detail via the density functional theory, molecular dynamics (MD) simulation, and quantitative structure-activity relationship (QSAR) methods. The main reactive site of an ionic liquid is located on its imidazolium ring. With alkyl chain lengthening or the introduction of methyl groups onto the imidazolium ring, its molecular reactivity and electron-donating ability increase the interaction between the ionic liquid and the Fe (110) surface. Therefore, the imidazolium rings of four IL inhibitors are more likely to lie on the Fe (110) surface in parallel through chemical adsorption. The interactions between N atoms in ionic liquids and the Fe (110) surface are stronger than those between the C atoms on the imidazolium rings of the four ionic liquid, and coordination bonds can be formed between N atoms and the Fe (110) surface. Therefore, ionic liquids can hinder the interaction between corrosion particles and the Fe (110) surface, hinder the diffusion of corrosion particles, and effectively reduce the number density of corrosion particles on the Fe (110) surface. A methyl substituent on the C2 atom of the imidazolium ring can enhance the electron-donating ability and adsorption tendency much more than an increase in the alkyl chain on the N3 atom. The four inhibitors are ordered in terms of corrosion inhibition efficiency as [C12DMIM]BF4 > [C10DMIM]BF4 > [C12MIM]BF4 > [C10MIM]BF4, which agrees well with the experimental results. A good correlation between experimental inhibition efficiency, concentration and microscopic structures parameters of ILs such as energy gap ΔE, polarizability P, electronegativity χ, hardness η, softness σ, number of electrons transferred ΔN, and electrophilicity ω was achieved.