The anti-corrosion behavior of azoles and their Schiff bases on copper in NaCl solution: experimental and theoretical approaches

Purpose This study aims to evaluate the anti-corrosion behavior of azole derivatives and their Schiff base compounds on copper in 3.5 Wt.% NaCl solution. The work addresses the limitation of conventional nitrogen-containing inhibitors and explores Schiff base modification as a strategy to enhance inhibition efficiency, adsorption stability and film integrity. Design/methodology/approach 2-aminoimidazole (A1), 4-amino-1,2,4-triazole (A2), 2-amino-benzimidazole (A3) and their Schiff base derivatives (A1-OH, A2-OH and A3-OH) were systematically investigated using potentiodynamic polarization curves and electrochemical impedance spectroscopy. The inhibition mechanism was further analyzed through Langmuir adsorption isotherm, contact angle measurement, quantum chemical calculation and molecular dynamics simulation. Findings All six compounds acted as mixed-type inhibitors by suppressing both anodic and cathodic reactions. Schiff base derivatives exhibited stronger adsorption capacity and higher efficiency than the parent azoles. Among them, A3–OH achieved the highest inhibition efficiency of 93.5% at 10 mM, attributed to the fused benzene–imidazole ring structure with an extended p-conjugated system and enhanced hydrophobicity. Schiff base moieties provided multiple adsorption-active sites (N atoms and C = N groups), strengthening coordination interactions and enabling stable parallel adsorption. These features facilitated the formation of compact, uniform and dense protective films, significantly improving corrosion resistance. Originality/value This work provides both theoretical and experimental evidence for the superior performance of Schiff base-modified azoles. The study highlights their multi-site reactivity, electronic optimization and excellent film-forming ability, underscoring their potential as green, high-efficiency copper corrosion inhibitors and offering guidance for the molecular design of sustainable protection strategies.