Diglycidyl amino benzene (DGAB) epoxy prepolymer was investigated using Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopy. Then, we highlighted the usefulness of DGAB epoxy prepolymer to improve the resistance of carbon steel (CS) in hydrochloric acid (1.0 M HCl) using weight loss (WL), electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PDP), scanning electron microscope (SEM), atomic force microscopy (AFM), density functional theory (DFT) and complexation calculations, molecular dynamics (MD) and mean square displacement (MSD) simulations. Highest inhibitory efficiencies for the WL, EIS and PDP methods at 10(-3) M of DGAB are 90.8, 96.3 and 95.9%, respectively. SEM and AFM micrographs demonstrated that the epoxy prepolymer could effectively block the acid attack by chemisorption on the surface of the carbon steel, the high correlation coefficient and low Standard Deviation (SD) and low Sum of Squares (SS) value gave the best fit for Langmuir isotherm. PDP data suggested that the epoxy prepolymer could provide excellent corrosion performance and showed a mixed-type inhibitor with predominant cathodic effectiveness. Investigate of the inhibitory layer and the potential mechanism was conceptually evaluated using DFT, MD simulations, radial distribution function (RDF) and mean square displacement (MSD). (C) 2020 Elsevier Inc. All rights reserved.