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This study investigates the potential of Laurus nobilis essential oil (LNEO) as a corrosion inhibitor for steel in a 1 M hydrochloric acid (HCl) solution.
Gas Chromatography-Mass Spectrometry (GC-MS) analysis was performed to determine the chemical composition of LNEO, revealing key constituents, including 1.8-cineole (33.47%), α-terpinyl acetate (17.39%), and sabinene (9.18%). Corrosion inhibition efficiency was evaluated through electrochemical techniques, and adsorption behavior was analyzed using the Langmuir isotherm model. Thermodynamic parameters were also assessed to elucidate the adsorption mechanism.
The inhibition efficiency reached a maximum of approximately 93.4% at an optimal concentration of 2 g/l. Langmuir adsorption isotherm studies confirmed a strong interaction between LNEO and the steel surface, with an adsorption free energy (ΔGads = -21.2 kJ/mol) and an adsorption equilibrium constant (Kads = 5.21 L/g), indicating a physisorption mechanism with partial charge transfer. Thermodynamic analyses showed an activation energy (Ea = 44.7 kJ/mol), enthalpy change (ΔHa = 42.1 kJ/mol), and entropy change (ΔSa = -69.3 J/mol.K), supporting a spontaneous and endothermic adsorption process.
Density Functional Theory (DFT) calculations and Scanning Electron Microscopy (SEM) analyses confirmed the adsorption mechanism, highlighting the protective film formation on the steel surface.
These findings demonstrate that Laurus nobilis essential oil is an effective corrosion inhibitor for steel in acidic media, with strong adsorption properties and high inhibitory efficiency.
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