Methanolic extract of Prasium majus as corrosion inhibitor of copper in HCl and HNO₃ solutions

This study presents the first investigation into the use of Prasium majus methanolic extract (PMME) as a novel green corrosion inhibitor for copper (Cu) in acidic solutions (1.0 M HCl and 1.0 M HNO3), with a focus on its effectiveness and inhibition mechanisms.Employing gravimetric, thermodynamic, electrochemical, microscopic, and spectroscopic analyses, the study aimed to evaluate PMME's effectiveness comprehensively.The weight loss measurement results proved that the efficiency of PMME as a corrosion inhibitor increased with the increase in concentration at 25C.The highest inhibition efficiency (IE%) was 96.4% in 1.0 M HNO3 and 89.8% in 1.0 M HCl at 6 hours and 500 mg/L.Efficiency increased with temperature, reaching 97.1% in HNO3 and 87.3% in HCl at 45C (500 mg/L).The adsorption characteristics of the corrosion inhibitor were evaluated using Temkin and Freundlich adsorption isotherms, which suggested a comprehensive adsorption mechanism.The potentiodynamic polarization measurements revealed that the PMME is a mixed-type corrosion inhibitor, it inhibits both the anodic and cathodic corrosion reactions of Cu by blocking the active sites of the metal surfaces.The calculated IE% reached 62.77% in HNO3 and 61.43% in HCl at 500 mg/L.The electrochemical impedance spectroscopy (EIS) results also indicated that the IE% of PMME in acidic solutions increased with its concentration, reaching 77.4% in HNO3 and 97.08% in HCl at 500 mg/L.Scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS) provided evidence that PMME interacted with Cu ions and contributed to the formation of a protective layer on the metal surfaces.It was concluded that PMME has the potential to be used as a corrosion inhibitor for the protection of Cu in acidic solutions.