High-performance green corrosion inhibitor for P11 steel in 1 M HCl with synergistic enhancement by KI

• N. Zavaleta-Gutierrez¹, L. Angelats-Silva², H. León-León² and N. Ñique-Gutierrez³

¹ Metallurgical Engineering Department, Trujillo National University, Av. Juan Pablo II s/n, Trujillo 13011, Peru
² Multidisciplinary Research Laboratory, Antenor Orrego Private University, Av. América Sur 3145, Trujillo 13008, Peru
³ Materials Engineering Department, Trujillo National University, Av. Juan Pablo II s/n, Trujillo 13011, Peru

Abstract: In this investigation, the corrosion inhibition capacity of linseed gum (LSG), a green biopolymer, was assessed for P11 steel in 1 M HCl, both individually and in conjunction with potassium iodide (KI), within a temperature range of 25–65°C. Gravimetric and electrochemical techniques, as well as Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and energy-dispersive spectroscopy (EDS), were implemented to analyze the inhibition mechanism and surface interactions. As a mixed-type inhibitor with mostly anodic control, LSG demonstrated considerable inhibitory efficiency, reaching up to 90% at 65°C. Thermodynamic investigations indicated a spontaneous and endothermic process including both physisorption and chemisorption mechanisms, and adsorption followed the Langmuir isotherm. The addition of 5 mM KI to the acidic solution containing 1 g·L^–1 of LSG improves the performance, reaching a maximum inhibitory efficiency of 96.5% at 65°C. The synergism parameters (S_θ<1) indicated that the adsorption mechanism was competitive rather than cooperative. The formation of a protective film on the steel surface was corroborated by electrochemical impedance spectroscopy and SEM/EDS results, which effectively mitigates corrosion damage. These findings emphasize the potential of LSG as an eco-friendly, effective corrosion inhibitor for P11 steel in acidic environments, particularly when combined with KI.

Keywords: linseed gum, green corrosion inhibitor, synergistic effect, P11 steel, acid corrosion, EIS

Int. J. Corros. Scale Inhib., 2025, 14, no. 3, 1154-1189
doi: 10.17675/2305-6894-2025-14-3-9

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