Weight loss (WL), electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization (PP) are utilized to investigate the effectiveness of prepared Schiff base N,N′-bis(salicylidene)-butylene-1,4-diamine (SB) as an inhibitor for the dissolution of carbon steel (CS) in 0.5 mol L-1 HCl. The SB structure is confirmed by 1HNMR and FTIR. The mitigation efficacy increased with raising the SB concentrations. The maximum efficacy is 84% at 300 ppm of the investigated inhibitor. However, at 300 ppm, the efficacy reduced from 84 to 80.7% when the temperature elevated from 298 to 333 K. The tested inhibitor reduced the corrosion current density (Icorr) and double-layer capacitance (Cdl) because of the growth of a protective film on the CS surface. The inhibitor matches the Langmuir adsorption isotherm and exhibits mixed-type inhibitor behaviour. The formation and adsorption of a consistent layer at CS in the availability of the SB compound were detected by SEM and EDX investigation. Density functional theory (DFT) and Monte Carlo (MC) simulations were employed to explain the nature of the interaction between the SB molecules and the CS. The SB compound's effectiveness as an inhibitor was supported by its quantum properties.