Electrochemical and theoretical studies on a bioactive Juniperus oxycedrus essential oil as a potential and ecofriendly corrosion inhibitor for mild steel in 1.0 M HCl environment

Abstract

This study focuses on exploring the corrosion inhibiting properties of the essential oil derived from Juniperus Oxycedrus (JO) originating from the Middle Atlas region in Morocco (Ait Attab) on mild steel in a 1.0 M HCl acid medium. This essential oil was analyzed using gas chromatography-mass spectrometry, which identified the major components of the inhibitor, primarily including bornyl acetate/C12H20O2 (31.17 %), Bicyclo [2.2.1] heptan-2-one, 1,7,7-trimethyl- (1S)/C10H16O (30.16 %), and α-pinene/C10H16 (9.88 %). The corrosion inhibition behavior was assessed using electrochemical measurements (potentiodynamic polarization measurements (PDP) and electrochemical impedance spectroscopy (EIS)) and thermodynamic parameters and kinetic (ΔHa, ΔSa et Ea). The result demonstrates that the essential oil of (JO) exhibits intriguing anticorrosive action, with an inhibition efficiency of 89.6 % at an inhibitor concentration of 2 g/L at 298°K. Additionally, the essential oil acts as a mixed-type inhibitor. Furthermore, EIS data and SEM/EDS analysis revealed that the nature of the adsorption of essential oil molecules on the mild steel surface is controlled by Langmuir adsorption isotherm, forming a protective film that shields the steel from acid attack. Density functional theory (DFT), molecular dynamic (MD) and Monte Carlo (MC) simulations were used to support the experimental results. The global and local chemical reactivity descriptors of the individual inhibitors were calculated using B3LYP functional, while the adsorption energy of the inhibitors on the steel surface were performed using MD and MC methods.