Synergistic experimental-computational insights into the protective mechanism of Chinese star anise essential oil on mild steel

초록

Driven by the pursuit of environmentally benign corrosion control methods, plant-derived essential oils have become attractive candidates owing to their low toxicity and notable inhibitory capabilities. Herein, Chinese star anise essential oil (CSAEO), extracted from Illicium verum, was systematically assessed as a corrosion inhibitor for mild steel (MS) in a 1 mol/L HCl solution. A multi-pronged experimental and computational methodology was employed, encompassing electrochemical measurements, surface examinations, and theoretical simulations. Notably, CSAEO at 2 g/L achieved a maximum inhibition efficiency of 93.4 % in 1 mol/L HCl, as evidenced by potentiodynamic polarization curves (PPC) and EIS measurements. Varying the dosage from 0.5 to 2 g/L revealed a concentration-dependent enhancement in corrosion protection, with 2 g/L emerging as the optimal concentration for mitigating steel degradation. Polarization studies revealed a mixed-type inhibition profile, leaning toward a cathodic mode. Subsequent scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) analyses confirmed the development of a defensive layer on the steel surface. A suite of theoretical studies, including Density Functional Tight Binding (DFTB), molecular dynamics (MD), and quantum chemical evaluations, provided additional insights into how CSAEO's key components attach to and arrange themselves on the mild steel surface, corroborating experimental data. Taken together, these findings underscore the promise of Chinese star anise essential oil as a sustainable, high-performance corrosion inhibitor with minimal environmental impact.

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