Bio-Based Corrosion Inhibition of Carbon Steel Using Ammi visnaga L. Essential Oil in Acidic Mediums: Experimental Analysis and Molecular Modeling

Bio-based corrosion inhibitor formulations are incredibly promising for mitigating corrosion, offering an environmentally sustainable approach while providing effective protection against material degradation. This study explores the corrosion inhibition potential of Ammi visnaga essential oil (AVEO) on carbon steel (CS) in a 1 mol/L hydrochloric acid (HCl) medium, combining electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PDP), linear polarization resistance (LPR), weight loss (WL) analysis, density functional theory (DFT), density-functional tight-binding (DFTB) modeling, and molecular dynamics (MD) simulation. The AVEO was extracted through hydrodistillation, and its chemical profile was characterized to identify key active compounds. EIS and PDP results revealed that the AVEO effectively inhibited corrosion through the formation of a protective layer on the steel surface, exhibiting inhibition efficiencies of up to 84% at 3 g/L, with a mixed-type corrosion inhibition action. Nyquist plots displayed an increased polarization resistance with the AVEO concentration, indicating an enhanced surface coverage and reduction in active corrosion sites. WL studies further supported these findings, showing decreased corrosion rates proportional to the AVEO concentration, while temperature variation studies showed a decreased performance at higher temperatures. Scanning electron microscope (SEM) analysis supported the formation of an effective protective layer on the CS surface upon the addition of AVEO to the HCl medium. DFTB modeling and MD simulations were employed to evaluate the interaction between major AVEO constituents and the steel surface, providing insight into the adsorption behavior and the electronic contributions at the molecule–metal interface. The combined experimental and theoretical findings indicate that AVEO holds promise as a natural, eco-friendly corrosion inhibitor, with implications for sustainable metal protection in acidic environments.