Inhibition impact of major active ingredients of Jordanian Peganum harmala on the corrosion rate of Cu, Fe and Al metals

The active components of Jordanian Peganum harmala L. (P. harmala) were investigated using both GC-MS and DFT calculations. The study focused on the methanol extract of P. harmala leaves, which was found to contain 21 significant natural components, of which 9 compounds constituted more than 2% of the total composition. These 9 compounds, including α-D-Glucopyranose (GLUC), Phenobarbital (PHEN), Melibiose (MELI), Cyanuric acid (CYAN), D-Glucuronic acid (GLUCU), Ethylamine (ETHY), 3-Hydroxysebacic acid (HYSE), 3-Hydroxytetradecanedioic acid (HYTD), and α-Tocopherol (TOCO), were evaluated as eco-friendly corrosion inhibitors for Al (Aluminium), Fe (Iron), and Cu (Cooper) metals using DFT calculations. The results showed that TOCO had the highest anti-corrosion performance among the 9 compounds, with Fe exhibiting the most inhibitory activity compared to Al and Cu. The high electrophilicity and Gibbs free energy of adsorbate value on metal surfaces made TOCO a distinguished corrosion inhibitor. The HOMO and LUMO gap of the inhibitors decreased in the following order: ETHY > GLUC > MELI > HYTD > HYSE > CYAN > GLUCU > PHEN > TOCO. These findings suggest that these chemicals may serve as environmental-friendly anticorrosion inhibitors for metal surfaces, although more in vitro experiments are needed to confirm these results.