Corrosion inhibition of St37 carbon steel under 15% H2SO4 using a novel Schiff Base: Experimental and computational insights

This study evaluates the corrosion inhibition performance of a novel Schiff base, (Z)-N-phenyl-2-((phenylimino)methyl)cyclohept-1-en-1-amine (BDS), on St37 carbon steel in 15 vol% H2SO4. Gravimetric and electrochemical analyses demonstrated that BDS significantly suppresses corrosion, achieving up to 98 % inhibition efficiency at 1250 ppm. While efficiency slightly decreased with increasing temperature and prolonged exposure, the compound maintained substantial protective capability. BDS acts as a mixed-type inhibitor, with its adsorption behavior following the Langmuir isotherm model. The calculated Gibbs free energy adsorption (ΔG*ads = –22.7 kJ mol−1) suggests a spontaneous physisorption mechanism. Surface characterization via SEM, EDS, FTIR, and XRD confirmed the formation of a compact, protective film on the steel surface. To complement the experimental findings, computational studies using DFT, COSMO-RS, and NCI analyses were performed. These revealed high molecular reactivity and the presence of stabilizing interactions that support physisorption. Key adsorption sites were identified at electron-rich nitrogen atoms and conjugated π-systems, aligning with the proposed inhibition mechanism. The synergy between experimental and theoretical results confirms that BDS is a highly effective and eco-friendly corrosion inhibitor, suitable for use in aggressive acidic environments common in industrial processes​.