Innovation in acid pickling treatments of copper by characterizations of a new series of Schiff bases as corrosion inhibitors

Purpose - Aims to investigate the inhibitive effect of the new series of Schiff base molecules, namely, N, N'-ethylen-bis(salicylidenimine) [S1], N, N'-isopropylen-bis(salicylidenimine) [S2] and N, N'-Ortho-phenylen acetyl acetone imine, (2-hydroxy Benzophenone imine) [S3] on corrosion of copper during acid pickling treatment in 1 M HCl solution. Effects of concentration and temperature on the inhibition efficiencies of the selected Schiff bases have been studied systematically. Design/methodology/approach - All inhibition experiments were conducted on copper sample in 1 M HCl solution. Weight loss measurements were carried out according to the ASTM standard procedure. Polarization curves and impedance spectra were carried out in a three-electrode cell assembly connected to an EG&G potentiostat M273 and frequency response analyzer M1025. Findings - Results obtained revealed that the studied Schiff bases act predominantly as cathodic inhibitors. The variations in inhibition efficiencies mainly depend on the type and nature of the inhibitors. Polarization and ac impedance measurements carried out at different concentrations of studied Schiff bases revealed that these compounds are adsorbed on copper surface and the adsorption obeys Langmuir adsorption isotherm. From the adsorption isotherms, the values of equilibrium constant, K-ads, and the free energies of adsorption, Delta G(ads), were calculated. The associated activation energy of corrosion and other thermodynamic parameters such as enthalpies and entropies have also been determined. Practical implications - The presence of high efficiency and low cost inhibitors is essential in acid pickling treatments for protection of copper and lowering of acid consumption. In comparison with conventional copper corrosion inhibitors such as benzotriazole, this result would be considered as a step forward in determination of new corrosion inhibitor. Originality/value - This paper reveals that Schiff bases can be successfully used for protection of copper surface in acid pickling solutions.