Eco-friendly Juniperus phoenicea essential oil–Zn 2+ hybrid inhibitor system for sustainable copper corrosion protection in acidic medium

The application of corrosion inhibitors constitutes one of the most efficient, cost-effective, and industrially practical strategies for mitigating the electrochemical degradation of metallic materials. The inhibition mechanism is mainly attributed to the adsorption of inhibitor molecules onto the metal/electrolyte interface, leading to the formation of a compact, adherent, and hydrophobic film that acts as a barrier against corrosive agents. In this study, we investigated the synergistic inhibition performance of a hybrid inhibitor composed of Juniperus phoenicea ssp. turbinate essential oil (HR) and Zn2+ ions for protecting copper in 0.5 M sulfuric acid solution (H2SO4). The inhibitory performance of the proposed inhibitor was investigated through potentiodynamic polarization and electrochemical impedance spectroscopy. The results revealed a substantial decrease in the corrosion rate, with an inhibition efficiency reaching approximately 90%. Surface characterization revealed the formation of a thin hydrophobic protective layer, which confirms the adsorption of the inhibitor onto the metal surface. The theoretical study of the proposed inhibitor was performed through Density Functional Tight Binding calculations and Density Functional Theory. The analysis of the calculated descriptors provided valuable insight into the adsorption behavior of the inhibitor on the copper surface. The interaction between Zn2+ ions and the main constituents of Juniperus phoenicea ssp. turbinate essential oil was found to be spontaneous, supporting the proposed inhibition mechanism. Overall, the proposed hybrid inhibitor demonstrated promising potential as eco-friendly inhibitor for protecting copper in industrial environments.