Mild steel corrosion inhibition by Lonicera subspicata var. johnstonii extract in 1 M HCl

• J. Chairez-Gonzalez¹, J. Salvador-Carlos¹, B. Valdez-Salas¹, E. Beltrán-Partida¹, P. Moe² and N. Cheng²

¹ Core Facility- Química y materiales avanzados, Instituto de Ingeniería, Universidad Autónoma de Baja California, Blvd. Benito Juárez and Normal s/n., 21280 Mexicali, Baja California, México
² Magna International Pte Ltd., 10 H Enterprise Road, Singapore 629834, Singapore

Abstract: The inhibitory potential of Lonicera subspicata var. johnstonii extract on AISI 1010 carbon steel in 1 M HCl was investigated by evaluating its efficiency, kinetics, adsorption mechanism, and molecular interactions at the metal–solution interface. Gravimetric analysis and electrochemical techniques revealed inhibition efficiencies in the range of 86–94% under static conditions, with a maximum of 94% at 2000 ppm, reducing the corrosion rate from 4.8 to 0.29 mm·y^–1. Potentiodynamic polarization showed a significant decrease in corrosion current density (from 1.12 to 0.07 mA·cm^–2) and small shifts in corrosion potential (<40 mV), indicating a mixed-type inhibition mechanism. Electrochemical impedance spectroscopy confirmed the formation of a stable protective film, with charge-transfer resistance (R_ct) increasing from 92 to 1650 Ω·cm² and double-layer capacitance (C_dl) decreasing by more than 70%. Surface characterization by scanning electron microscopy and energy-dispersive X-ray spectroscopy showed severe corrosion damage and oxygen-rich oxides in the blank sample, in contrast to smooth, homogeneous surfaces with minimal degradation in the inhibited specimens, supporting the presence of an adsorbed inhibitor layer. Density functional theory calculations were performed using luteolin, a major flavonoid in the extract, as the representative molecule. Frontier orbital analysis showed a HOMO–LUMO gap of 3.21 eV, and adsorption energy of –2.34 eV on Fe (110), indicating electronic stability and strong chemisorption interactions. The combined experimental and theoretical findings demonstrate that L. subspicata extract is an efficient (≥90%), sustainable, and promising corrosion inhibitor for carbon steel in acidic environments.

Keywords: green corrosion inhibitor, mild steel protection, adsorption mechanism, acidic medium corrosion, genus Lonicera

Int. J. Corros. Scale Inhib., 2025, 14, no. 4, 1974-1999
doi: 10.17675/2305-6894-2025-14-4-14

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