A simple Schiff base compound as mitigator for the destruction of C-steel in HCl aqueous solutions: practical and theoretical studies

Abstract The corrosion inhibition performance of N-(1-methylpyrrolidin-2-ylidene) benzo[d]thiazol-2-amine (MPBA) for carbon steel in 1.0 M HCl solution was systematically investigated using chemical and electrochemical techniques. The corrosion rate decreased markedly with increasing MPBA concentration. Inhibition efficiency increased progressively with inhibitor concentration, reaching values exceeding 97.0% at 5 mM and 298 K. The inhibition mechanism was primarily governed by the adsorption of MPBA molecules onto the carbon steel surface and was well described by the Langmuir adsorption isotherm. The negative values of the standard Gibbs free energy of adsorption (Δ G ads ) confirm the spontaneous nature of the adsorption process. Depending on temperature, Δ G ° ads values ranged from − 37.75 to − 36.20 kJ mol⁻¹, indicating a mixed physisorption–chemisorption mechanism. The observed decrease in the adsorption equilibrium constant ( K ads ) with increasing temperature can be attributed to the partial desorption of MPBA molecules from the carbon steel surface. Density functional theory (DFT) calculations combined with the conductor-like polarizable continuum model (CPCM), along with Monte Carlo and molecular dynamics simulations, further confirmed the strong adsorption affinity of MPBA toward the steel surface, thereby supporting its excellent corrosion inhibition performance.