ELECTROCHEMICAL EVALUATION OF CUCURBITA PEPO LEAF EXTRACT AS A GREEN CORROSION INHIBITOR

Abstract

Corrosion of iron in acidic media remains a major industrial challenge, creating a need for environmentally friendly corrosion inhibitors. In this study, the corrosion inhibition performance of Cucurbita pepo leaf extract as a surface pretreatment for mild iron electrodes in 1 M HCl was evaluated using potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and thermodynamic analyses. Particular attention was given to the effects of immersion time and temperature on the inhibition mechanism.
The electrochemical results showed a progressive improvement in inhibition efficiency with increasing immersion time. The pretreated electrodes exhibited a marked decrease in corrosion current density, and polarization measurements revealed a maximum inhibition efficiency of 97.46% after 24 h at 20 °C. The small shift in corrosion potential and the variation of both anodic and cathodic Tafel slopes indicated mixed-type inhibition behavior. EIS measurements confirmed the enhanced corrosion protection, with the charge transfer resistance increasing from 12.8 Ω for the blank solution to 211.2 Ω after 24 h of immersion.
Thermodynamic analysis showed an increase in activation energy from 12.473 to 37.264 kJ mol⁻¹ in the presence of the extract, indicating a less favorable corrosion process. Increasing temperature reduced the inhibition efficiency, suggesting partial destabilization of the adsorbed protective layer. Overall, Cucurbita pepo leaf extract acts as an effective green corrosion inhibitor through adsorption-driven formation of a protective surface film.