Enhancing corrosion resistance in HCl environments: Comparative efficacy of a conjugated 3ph-Schiff base versus benzotriazole

This research addresses the need for effective corrosion inhibitors in industrial applications, evaluating the performance of 4-nitro-2-(((1E,2E)-3-phenylallylidene)amino)aniline (noted as 3ph-Schiff base) as a corrosion inhibitor in comparison to benzotriazole (BTA) in a high-concentration 3 M HCl environment. Unlike studies conducted in lower concentrations (e.g. 0.1 and 1 M), this study aims to assess inhibitor performance under more aggressive conditions. Rigorous methods, including Tafel polarisation, electrochemical impedance spectroscopy (EIS), and mass loss measurements, revealed variations in inhibition efficiency (IE). Polarisation data indicated that 3ph-Schiff base at 0.3% (approximately 8.96 mM) achieved a maximum IE of 99.5%, surpassing BTA at the same concentration (approximately 25.2 mM), which recorded an IE of 96.9%. Meanwhile, EIS analysis yielded slightly lower IE values, with 3ph-Schiff base reaching 90.21% and BTA 67.39%, reflecting the complementary nature of these methods. The corrosion inhibition mechanism of 3ph-Schiff base is attributed to strong adsorption on the metal surface, where amino (NH ₂ ) and nitro (NO ₂ ) groups promote stable complex formation with metal ions, enhancing electron donation and forming a protective layer that blocks corrosive agents. Scanning electron microscopy and elemental mapping confirm uniform nitrogen and carbon surface coverage, integral to the protective layer. This layer acts as both a physical barrier and an electrochemical passivator, effectively reducing anodic and cathodic reactions. The combined effects of adsorption, physical blocking and passivation underscore the 3ph-Schiff base's superior performance as a corrosion inhibitor in acidic environments.