Synergistic Corrosion Inhibitory Effects of Rice and African Bread Fruit Husks Extract on Mild Steel in HNO3 Medium

Abstract

This study investigates the synergistic corrosion inhibition efficiency of Rice and African Breadfruit Husk extracts on mild steel in a 1 M nitric acid solution. The extracts were prepared by soaking both husks in ethanol and removing them via the solvent extraction method. Their phytochemical compositions were confirmed using Fourier Transform Infrared (FTIR) and Gas Chromatography-Mass Spectrometry (GC-MS) analyses. Corrosion inhibition was evaluated through electrochemical impedance spectroscopy (EIS) and Potentiodynamic Polarization (PDP). Results show that the combination of Rice and African Breadfruit Husk extracts significantly reduces corrosion rate with increasing inhibitor concentration. The highest inhibition efficiency of 96.5% was obtained using the electrochemical method, suggesting a strong synergistic effect. The adsorption of the inhibitors followed the Langmuir isotherm, indicating monolayer formation, and the thermodynamic parameters suggested physisorption as the predominant mechanism. The corroded metals were examined using Scanning Electron Microscopy (SEM). This research highlights the potential of agricultural waste-based green inhibitors as sustainable, low-cost, and environmentally friendly alternatives to toxic synthetic corrosion inhibitors. Nitric acid was selected due to its aggressive oxidizing nature, which makes corrosion particularly challenging. To the best of our knowledge, this is the first report introducing African breadfruit husk extract as a corrosion inhibitor and demonstrating its synergistic effect with rice husk in nitric acid medium.