Enhanced corrosion inhibition of low carbon steel in HCl medium using 1-benzyl-5-imino-3-hydroxypyrazoline: a comprehensive study

• A.W. Saeed¹, H. Al-Luaiby², A. Mohammed³, T.S. Gaaz⁴ and A. Alamiery⁵

¹ College of Renewable Energy Sciences and Environmental, Alkarkh University of Science, Baghdad 10001, Baghdad, Iraq
² College of Energy and Environmental Sciences, Al-Karkh University of Science, Baghdad 10001, Baghdad, Iraq
³ Department of Electromechanical Engineering, University of Technology-Iraq, P.O. Box: 10001, Baghdad, Iraq
⁴ Air Conditioning and Refrigeration Techniques Engineering Department, College of Engineering and Technologies, Al-Mustaqbal University, 51015 Babylon, Iraq
⁵ Al-Ayen University, Nile St, Nasiriyah, 64001, Dhi Qar, Iraq

Abstract: This research explores the corrosion inhibition efficiency of 1-benzyl-5-imino-3-hydroxypyrazoline (BIHP) for low carbon steel in hydrochloric acid (HCl) solution. The study assesses BIHP’s performance using weight loss measurements, and density functional theory (DFT) calculations. Experimental results demonstrate that BIHP offers an impressive inhibition efficiency of 93% at 303 K during a 5-hour immersion period. Weight loss measurements show a significant decrease in corrosion rates with increasing immersion times (1, 5, 10, 24, and 48 hours), with the inhibition efficiency stabilizing after 10 hours. Furthermore, an increase in inhibition efficiency was demonstrated with increasing temperature from 303 to 333 K. The adsorption of BIHP molecules on the low-carbon steel surface followed the Langmuir model suggesting both physical and chemical adsorption mechanisms. With the help of density functional theory calculations, the most important parameters related to the molecular ability as corrosion inhibitors including the E_HOMO, E_LUMO, E_gap, and issues related to chemical reactions, including total hardness (η), electronegativity (χ), and electron fraction transitions from the anti-corrosion molecule to the low carbon steel (ΔN), were calculated.

Keywords: corrosion, hydroxypyrazoline, weight loss, DFT, mechanisms

Int. J. Corros. Scale Inhib., 2025, 14, no. 1, 333-352
doi: 10.17675/2305-6894-2025-14-1-21

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