Polar group substituted imidazolium zwitterions as eco-friendly corrosion inhibitors for mild steel in acid solution

[Display omitted] •Substituted imidazolium zwitterions were synthesized using principles of green chemistry.•The zwitterions were evaluated as corrosion inhibitors for mild steel in 1 M HCl.•Sulfur containing inhibitor Z-2 shows excellent inhibition efficiency of 94.59% at a dose of 6.01 × 10−6 mol L−1 (2 ppm).•AFM, SEM and XPS studies support the formation of inhibitor film on mild steel surface.•Computational studies show predominant interaction of protonated forms of inhibitors with the metal surface. Two polar group substituted imidazolium zwitterions have been synthesized and investigated as corrosion inhibitors for the first time on mild steel in HCl solution using chemical and electrochemical methods. Sulphur containing zwitterion (Z-2) gave excellent inhibition efficiency of 94.59% at a concentration of 6.01 μmol L−1 (2 ppm), while hydroxyl-containing zwitterion (Z-1) exhibited 94.86% IE at 150.4 μmol L−1 (50 ppm). Surface analyses supported the formation of inhibitor film on the metallic surface. Adsorption of zwitterions obeyed Langmuir adsorption isotherm. Quantum chemical (QC) calculation and molecular dynamics simulations studies further supported the experimental results.