Comparative study of plantain peel and stem extracts as eco-friendly corrosion inhibitors for mild steel and aluminium in 0.5m H2So4

Corrosion is a widespread problem that affects metallic materials, resulting from the thermodynamic instability of metals when exposed to moisture, water, or oxidizing agents. This slow and irreversible degradation occurs through chemical reactions between metals and their environment, presenting significant challenges across various industries. This research investigates the potential of unripe plantain peel and stem extracts as alternatives to conventional chemical inhibitors for mild steel and aluminium in sulphuric acid..The method of weight loss measurements were employed to evaluate the corrosion inhibition performance on metal coupons. The study also characterized the bioactive chemicals in the extracts using Gas Chromatography-Mass Spectrometry (GC-MS), identifying thirty significant compounds, including stigmasterol, carpaine, cedrene, benzoic acid, pyrogallol, epicatechin, gallocatechin, and p-coumaric acid ethyl ester, which demonstrated protective properties against sulfuric acid-induced corrosion. The extraction yields were found to be satisfactory, with plantain peel yielding 38.46%, significantly higher than the 19.14% yield for the plantain stem. This difference highlights the varying richness in their bio-active chemicals between the two plant extracts. Corrosion inhibition efficiencies of 98.43% for aluminium and 93.76% for mild steel were observed with plantain peel extract, while the stem extract showed efficiencies of 94.27% for aluminium and 86.63% for mild steel. These efficiencies, attributed to surface adsorption, were higher for aluminium across both extracts. The Gibbs free energy of adsorption (ΔGads) values, ranging from -19 to -20 kJ/mol, indicate spontaneous physio-adsorption, demonstrating the ease of desorption under suitable condition.