Euphorbia neriifolia extracts as green corrosion inhibitors for aluminium in hydrochloric and nitric acid media

Abstract Among the new, significant approaches for preventing corrosion in contemporary culture is using green corrosion inhibitors, which lower corrosion rates to an acceptable level with minimal negative effects on the environment. This area of investigation has witnessed substantial advancements from the environmental sustainability perspective. This study investigates the corrosion inhibition potential of Euphorbia neriifolia extracts on aluminium in various concentrations of hydrochloric acid (HCl) and nitric acid (HNO₃) using weight loss, thermometric methods, and Field Emission Scanning Electron Microscopy (FESEM) analysis. The weight loss method revealed maximum inhibition efficiencies of 94.92% and 92.62% for the stem extract at a concentration of 0.7% in 1 M HCl and 1 M HNO₃, respectively. The Langmuir adsorption isotherm indicated a strong linear relationship between surface coverage and inhibitor concentration, suggesting favorable monolayer adsorption on the aluminum surface. Thermometric analysis confirmed the efficacy of the extracts, with a significant reduction in corrosion rates from 157.89 mm/yr in the absence of inhibitors to 0.0099 mm/yr with the optimal concentration of stem extract in 1 M HCl. FESEM images illustrated a marked difference in surface morphology, revealing a smooth, intact surface in the presence of the extracts compared to rough, pitted surfaces in the control samples exposed solely to acidic environments. This work demonstrates the high efficacy and potential modes of action through adsorption of Euphorbia neriifolia extracts, drawing attention to their intriguing use as environmentally benign corrosion inhibitors. The results offer a new, biodegradable substitute for traditional synthetic inhibitors and add to the expanding corpus of research supporting sustainable corrosion management techniques. Graphical Abstract