From nature to protection: Unleashing the protective potential of Hedera helix leaves against corrosion in harsh acidic environments using experimental and theoretical insights

The corrosion of metals is a major problem in many industrial sectors. To develop sustainable and naturally friendly alternatives to classical corrosion inhibitors, the use of plant extracts has attracted increasing interest. Plant extracts contain a variety of bioactive substances, such as polyphenols, which have corrosion-inhibitory properties. Plant extracts are biodegradable and pose minimal risk to human health and ecosystems. Consistent with the prevailing research trends in this field, in this study, the ability of Hedera helix leaf extract (HHLE) to protect XC18 steel from corrosion in 1 M HCl was evaluated. The polyphenols present in HHLE were identified using HPLC-DAD analysis. The weight loss, potentiodynamic polarization (PDP), and electrochemical impedance spectroscopy (EIS) measurements were examined. Six phenolic compounds were detected in HHLE. The results showed that the inhibitory efficiency of the leaf extract increased with increasing concentration. At 298 K, weight loss corrosion and electrochemical tests demonstrated that the greatest protection efficiency of 92.67 % for the steel was achieved at a concentration of 1000 mg/L of HHLE. This was attributed to a reduction in the cathodic currents and the obstruction of the active corroding sites. Thermodynamic analysis indicated an endothermic process governed by physisorption, and the Langmuir adsorption isotherm model highlighted the influence of both physical and chemical mechanisms on the adsorption process. Scanning electron microscopy (SEM) was used to confirm the reduction in XC18 steel corrosion in the presence of HHLE. Density functional theory (DFT) was employed to carry out quantum chemistry studies on the two primary components of the extract: kaempferol (KMP) and trans-chalcone (CHL). The quantum parameters obtained from the calculations were used to explore the active sites and interactions between donor and acceptor molecules, as well as the interfacial mechanism behavior of HHLE molecules on the metal surface.