Eco-friendly corrosion protection of steel using Thymus satureioides leaves oil: experimental and theoretical studies

This work investigates the corrosion inhibition performance of Thymus satureioides oil (TSO) for steel in 1 M HCl solution using electrochemical techniques. Gas chromatography analysis showed that the main components of TSO are borneol (33.58%), linalol (15.67%), camphene (14.47%), α-pinene (7.67%), and carvacrol (6.53%). Potentiodynamic polarization results indicated that TSO acts as a mixed-type inhibitor. Electrochemical impedance spectroscopy showed the formation of a protective film on the steel surface, leading to increased charge transfer resistance and reduced double-layer capacitance. The inhibition efficiency reached 92.3%. The corrosion behavior was also studied at different temperatures. Density functional theory calculations were performed using the B3LYP/6-311+G(2d,p) method with the polarized continuum solvent model in water. Fukui function analysis was used to identify the most reactive sites for electrophilic and nucleophilic attacks. The theoretical results showed that camphene has the strongest interaction with the metal surface, followed by linalol and borneol. Overall, TSO can be considered an effective and eco-friendly corrosion inhibitor for steel in acidic media.