Rosemary Essential Oil as a Sustainable Corrosion Inhibitor for Copper: Quantum Chemical Insights, Characterization, Adsorption Mechanisms applying Monte Carlo, and POM analysis
Wafaa Zriouel
Abstract
This study uses computational approaches to predict and investigate the inhibition behavior of rosemary essential oil (REO) as a green corrosion inhibitor. These approaches are based on calculating quantum parameters and Mulliken atomic charges using Density Functional Theory (DFT) combined with a Monte Carlo simulation to explain the adsorption mechanism and a POM (Petra/Osiris/Molinspiration) analysis. The chemical composition analysis revealed eucalyptol (49.01%), alpha-pinene (17.31%), and beta-caryophyllene (6.42%) as the major constituents. Quantum chemical calculations identified alpha-thujene, beta-myrcene, and alpha-pinene as key inhibitors based on their electron-donating abilities, moderate energy gaps, and higher softness values, indicating a strong potential for adsorption onto metal surfaces. Mulliken charge analysis highlighted the significance of oxygenated compounds, especially alpha-terpineol, due to its highly negative oxygen charges, which suggest strong interactions with metal surfaces. Monte Carlo simulations showed that gamma-cadinene exhibited the highest adsorption energies in both gas (-53.259 kJ/mol) and aqueous (-631.011 kJ/mol) phases, indicating a robust interaction with the copper surface. Humulene and alpha-terpineol also showed significant adsorption characteristics. The OSIRIS and Molinspiration assessments confirmed the molecules' environmental safety and balanced lipophilicity, which enhanced their corrosion inhibition capabilities. The results indicate that the corrosion inhibition of the Rosemary essential oil is due to a combination of physical and chemical adsorption mechanisms, with possible synergistic effects among its constituents, making it an effective and sustainable corrosion inhibitor. These computational insights provide a foundation for understanding REO's behavior before progressing to experimental electrochemical evaluations.