Properties of Avocado (Persea Americana) Leaf Extract as a Corrosion Inhibitor for Mild Steel in 1 M KOH

Abstract

This study investigates the corrosion inhibition performance of a synthesized inhibitor on mild steel in an aggressive corrosive environment using complementary electrochemical and gravimetric techniques. Weight-loss measurements conducted over a 5-hour immersion period revealed substantially higher corrosion rates in the uninhibited (blank) medium compared to the inhibited systems. The blank samples recorded weight losses of 0.0012 g, 0.0020 g, 0.0012 g, 0.0022 g, and 0.0001 g at 1, 2, 3, 4, and 5 hours respectively, confirming the high corrosivity of the medium. In contrast, the inhibited systems demonstrated marked reductions in weight loss, with the most effective inhibition occurring at concentrations of 0.3 g/L and 0.4 g/L. At 1 hour, the 0.4 g/L concentration produced the lowest weight loss of 0.0002 g. At 2 hours, 0.3 g/L yielded the minimum weight loss of 0.0003 g, while at 3 hours, 0.1 g/L and 0.4 g/L recorded losses of 0.0002 g and 0.0012 g respectively. A transient anomaly was observed at 4 hours for the 0.3 g/L concentration, which showed a peak weight loss of 0.0088 g, suggesting momentary disruption of the protective film. By 5 hours, the inhibited systems stabilized, with all concentrations recording moderate weight losses ranging from 0.0003 to 0.0007 g. Electrochemical analysis using potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) supported the gravimetric findings. The addition of the inhibitor led to a significant reduction in corrosion current density and an increase in charge-transfer resistance, indicating strong surface adsorption and barrier formation. The 0.4 g/L concentration exhibited the highest inhibition efficiency, consistent with the lowest weight-loss values obtained in the gravimetric tests. The combined results confirm that the inhibitor acts as an effective adsorptive corrosion barrier, capable of suppressing both anodic and cathodic processes. Overall, the study establishes that the synthesized inhibitor provides substantial corrosion protection for mild steel, with optimal performance at concentrations between 0.3 g/L and 0.4 g/L. The strong agreement between gravimetric and electrochemical data reinforces the reliability of the findings and demonstrates the potential applicability of the inhibitor in industrial. Keywords: