Analysis of a Mixture of Banana Peel and Rice Straw Extracts for Inhibiting Corrosion of Carbon Steel in Hydrochloric Acid Solution

Preventing metal corrosion is one of the most pressing issues in the modern world. One of the most effective ways to combat corrosion is to use inhibitors. Currently, much research is devoted to the study of green corrosion inhibitors obtained from plant extracts and agricultural waste. In this study, banana peel extract, rice straw extract, and their mixture as green corrosion inhibitors of carbon steel samples in 1 M HCl solution were examined by weight loss, electrochemical, and scanning electron microscopy methods. The experimental results showed that the mixture of extracts (40:60 banana peel and rice straw) had a higher inhibitory capacity than the individual inhibitors. At 750 ppm after 24 h of immersion, the inhibition of banana peel, rice extract, and the suggested mixture was 77.87, 95.03, and 96.36%, respectively. Furthermore, the mixture exhibited a maximum synergistic inhibition value of 1.65, indicating a 65% increase in inhibition efficiency when using the mixture instead of the extract alone. Nyquist plots obtained from electrochemical experiments confirmed the optimum concentration value of 750 ppm for banana peel extract, rice extract, and their mixture. These tests also show that the diameter of the semicircles in the presence of the mixture was larger than in the case of the extract alone, indicating a higher inhibitory capacity of the mixture. Moreover, scanning electron microscopy analysis showed the formation of a stable protective film on the metal surface. Finally, adsorption analysis showed the presence of both physical and chemical adsorptions of all the extracts used, which was obtained using the Langmuir isotherm.