CORROSION CONTROL ON LOW-CARBON STEEL USING GUAVA LEAF EXTRACT (PSIDIUM GUAJAVA) AS AN ORGANIC INHIBITOR

This study investigates the use of guava leaf extract (Psidium guajava) as an organic corrosion inhibitor for low-carbon steel in a carbonic medium. Corrosion of steel remains a critical global issue, with its annual cost estimated to exceed $2.5 trillion, representing approximately 3.4% of the world’s GDP. This necessitates an environmentally friendly alternative to traditional toxic synthetic inhibitors. The research method involved preparing the extract and conducting corrosion tests on mild steel coupons (with a carbon content of less than 0.25%). Experiments were carried out in a 1M HCl acidic medium using techniques such as weight loss measurements, potential dynamic polarization, and EIS, across a temperature range of 25–60°C and a pH range of 2–6. The study focused on short-term exposure (up to 24 hours) to assess the initial inhibition efficiency. The guava leaf extract proved to be a highly effective inhibitor. Statistical validation via ANOVA established the model's significance with an extremely high Model F-value of 921.10 and a p-value of < 0.0001 for Inhibition Efficiency. The predictive power was robust, as indicated by a Predicted R² of 0.9945 being in reasonable agreement with the Adjusted R² of 0.9978 , and an Adequate Precision ratio of 79.032. Time and Temperature were confirmed as the only statistically significant model terms, suggesting the corrosion process is under kinetic control. The numerical optimization demonstrated that a near-maximum predicted efficiency could be achieved at the lowest inhibitor dosage, supporting the extract's high potency and cost-effectiveness. In conclusion, the guava leaf extract successfully performed as an environmentally sustainable corrosion inhibitor. The inhibition mechanism was determined to be chemisorption, driven by the active phenolic groups and aromatic rings in the extract, which form a compact protective barrier on the steel surface.