Experimental approaches and computational modeling to investigate the impact of tangerine peel extract on steel corrosion in an acidic environment

This study investigates the corrosion inhibition of tangerine peel extract (TPE) as a sustainable inhibitor for carbon steel in 1 M H₂SO₄, using electrochemical techniques, surface analysis, and computational methods. Electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PDP), and weight loss measurements reveal that TPE achieves inhibition efficiencies of 83–88 % at concentrations of 200–1000 ppm, indicating exhibiting both anodic and cathodic suppression. EIS results suggest the formation of a protective layer on the steel surface, reducing corrosion rates. Fourier-transform infrared (FT-IR) spectroscopy identified key functional groups in TPE, such as organic acids, flavonoids, carbonyls, and alcohols, which contribute to its inhibition properties. Field-emission scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM) analyses show a 25 % reduction in surface degradation and roughness with TPE. The adsorption free energy of −16.8 kJ/mol suggests physical adsorption on the steel surface. Molecular dynamics (MD) and Monte Carlo (MC) simulations on the Fe (110) plane, along with quantum chemical calculations, indicate favorable adsorption with a HOMO-LUMO energy gap of 2.504 eV (HOMO: −5.211 eV, LUMO: −2.707 eV). These findings highlight TPE as a promising eco-friendly corrosion inhibitor, although further studies are needed to optimize its application and compare its performance with existing plant-based inhibitors.