Investigating the potency of new imidazolium ionic liquids in preventing carbon steel corrosion in acidic conditions: An integrated experimental and DFTB semi-empirical approach

[Display omitted] •Up to 97 % corrosion inhibition in 1 M HCl by new imidazolium ionic liquids.•Lower efficacy of nitro-substituted ILs in steel protection.•DFTB simulations validate ILs’ covalent bonding with iron atoms. The persistent issue of carbon steel corrosion has led to extensive investigations, with ionic liquids emerging as a promising solution for mitigating this problem. This research assesses the corrosion inhibiting capabilities of four novel imidazolium ionic liquids (ILs), namely 1-benzyl-3-(2-nitrobenzoyl)-1H-imidazol-3-ium chloride (BNIC), 1-acetyl-3-(2-oxo-2-phenylethyl)-1H-imidazol-3-ium bromide (APIB), 1-acetyl-3-(2-(4-fluorophenyl)-2-oxoethyl)-1H-imidazol-3-ium bromide (AFIB), and 1-acetyl-3-(2-(4-chlorophenyl)-2-oxoethyl)-1H-imidazol-3-ium bromide (ACIB) for carbon steel in a 1.0 M acidic environment. A combination of experimental approaches, including electrochemical techniques, and theoretical Density Functional based Tight Binding (DFTB) modeling, were employed to evaluate the corrosion of carbon steel both with and without these inhibitors. The ILs demonstrated impressive inhibition efficiency, reaching up to 97 %. Notably, while most compounds offered significant protection, the Nitro-substituted IL exhibited the least effectiveness. The introduction of these compounds into the acidic solution significantly reduced the double layer capacitance and markedly increased the polarization resistance, indicating the adsorption of inhibitor molecules onto the metal surface. Density Functional Theory Based Tight Binding (DFTB) simulations supported these findings by confirming the establishment of covalent bonds between the inhibitor molecules and iron atoms. The study also reaffirmed the detrimental impact of nitro group substitution on the corrosion inhibition performance of corrosion inhibitors.