Corrosion inhibition and <i>in silico</i> toxicity assessment of imidazo[1,2-<i>a</i>]pyrimidine-Schiff base derivatives as effective and environmentally friendly corrosion inhibitors for mild steel

This study reports the synthesis and corrosion inhibition evaluation of two imidazo[1,2-<i>a</i>]pyrimidine-Schiff base derivatives (IPY 1 and IPY 2) for mild steel (MS) in 1.0 M HCl solution. Using weight loss (WL), potentiodynamic polarization (PDP), and electrochemical impedance spectroscopy (EIS), both compounds demonstrated excellent inhibition efficiencies, 96.10% for IPY 2 and 94.22% for IPY 2, at 10^-3 M and 298 K. The effects of temperature and immersion time were also investigated, revealing stable performance over extended exposure. Thermodynamic analysis showed that both compounds followed the Langmuir adsorption isotherm, with high adsorption equilibrium constants (<i>K</i> _ads = 1.39 × 10⁵ M^-1 for IPY 2 and 1.48 × 10⁵ M^-1 for IPY 2) and negative free energy values (Δ<i>G</i> _ads° = -39.29 and -39.44 kJ mol^-1), indicative of spontaneous, mixed-mode adsorption. Surface characterization <i>via</i> Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), FT-IR, UV-visible spectroscopy, and contact angle measurements confirmed the formation of a compact, hydrophobic protective layer on the steel surface. The inhibition mechanism was further elucidated through Density Functional Theory (DFT), Monte Carlo (MC), and Molecular Dynamics (MD) simulations, which supported the strong interaction between the inhibitor molecules and the MS surface. Additionally, <i>in silico</i> toxicity assessments revealed low bioaccumulation potential, good biodegradability, and acceptable safety profiles, supporting the environmental compatibility of these compounds. Together, the integration of experimental, theoretical, and toxicological analyses highlights IPY 1 and IPY 2 as efficient, stable, and eco-friendly corrosion inhibitors with strong potential for sustainable industrial applications.