Green Approach to Corrosion Control of Mild Steel in H3PO4 Using Chromolaena odorata Leaves Extract: Optimization

This study investigated the optimization and effectiveness of corrosion control of Chromolaena odorata leaves extract (COLE) on mild steel in H₃PO₄. Box–Behnken design was used in this study to determine the influence of variables: temperature (30–60 °C), inhibitor concentration (0.2–0.8 g/l), and duration of immersion (3–12 days) on corrosion rate. The extract was subjected to phytochemical analysis to determine the quantitative and qualitative quantities of bioactive constituents in COLE. Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR) were used to characterize the samples. The result of phytochemical analysis showed the presence of bioactive constituents that extract makes extracts a good inhibitor. The optimal process conditions observed were as follows: time: 7.5 days, temperature: 45 °C, and inhibition concentration: 0.5 g/l with corrosion rate of 0.0002650 g/mm²days. The SEM and FT-IR result from the validated experiment revealed that compared to mild steel which corrodes at the slowest rate, more passive films were seen due to absorption. The inhibitive potential of Chromolaena odorata leaves extract is a good corrosion inhibitor in the acidic environment.