Sustainable materials encompass a diverse range of substances used in both consumer and industrial domains. These materials are sourced in quantities that safeguard non-renewable resources and environmental equilibrium, with a focus on bio-based alternatives derived from plants. This study investigates the corrosion inhibition potential of two distinct Blue Tansy essential oils (BTES 1 and BTES 2) with varying chemical compositions. Corrosion resistance for mild steel in 1 M HCl environment was assessed using weight loss and Potentiodynamic polarization techniques. The evaluation of BTES 1 and BTES 2 revealed compelling insights. Notably, their inhibition efficiency exhibited an intriguing, damped oscillation pattern with fluctuating concentrations. Remarkably, at 0.5 g/L concentration, BTES 1 achieved an impressive 80% inhibition, while BTES 2 demonstrated a substantial 70% inhibition at 2.5 g/L. This behavior stems from intricate interactions among active compounds, leading to protective film formation and competitive adsorption effects. Importantly, congruence between weight loss measurements and potentiodynamic polarization curves fortified the reliability of outcomes. The study also confirmed BTES as a mixed-type inhibitor, as indicated by polarization curves. Furthermore, Petra/Osiris/Molinspiration (POM) analyses were conducted to unravel molecule interactions, elucidate toxicity risks, and assess bioactivity scores. This comprehensive exploration sheds light on the interplay between sustainable materials, corrosion inhibition efficacy, and complex molecular dynamics, enhancing our understanding of environmentally conscious corrosion prevention strategies.

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.

This work explores the potential of rosemary essential oil (REO) as an environmentally friendly corrosion inhibitor for low-alloy steel in 1 M H ₂ SO ₄ . The chemical composition of the oil, dominated by eucalyptol and α-pinene, was first established by GC-FID analysis. The inhibitory performance of REO was evaluated using gravimetric measurements, potentiodynamic polarization, electrochemical impedance spectroscopy, and temperature-dependent tests. These experiments consistently showed that REO reduces the corrosion rate by forming a protective layer on the steel surface, with optimal performance observed at 1.5 g/L. The decrease in corrosion current density, the widening of the Nyquist loops, and the reduction in double layer capacitance confirm the progressive coverage of the surface achieved by the active constituents of the oil. Thermodynamic and kinetic parameters further indicate that the inhibitor increases the energy barrier of the corrosion reaction and maintains good stability at high temperatures. Adsorption studies have revealed that REO constituents follow a Langmuir adsorption model and exhibit spontaneous adsorption due to a strong affinity with the metal surface. Additional DFT calculations, molecular electrostatic potential (MEP) analyses, and Monte Carlo simulations highlight the predominant role of oxygenated monoterpenes, particularly eucalyptol, isoborneol, and terpineols in stabilizing the organic film through electron-donating interactions.