https://doi.org/10.1140/epjp/s13360-025-07008-2
Regular Article
Inhibition performance and adsorption behavior of expired drug loperamide on mild steel in 0.5 M hydrochloric acid: experimental and theoretical evaluation
1
Department of Applied Sciences, Division of Chemistry, Chandigarh University, 140301, Gharuan, Mohali, Punjab, India
2
Department of Chemistry, Bahra Research Innovation and Knowledge Cluster, Rayat Bahra University, Chandigarh-Ropar NH 205, 140103, Greater Mohali, Punjab, India
Received:
8
September
2025
Accepted:
28
October
2025
Published online:
10
November
2025
Expired pharmaceutical compounds can serve as sustainable corrosion inhibitors, providing an eco-friendly alternative to conventional chemicals. This study aims to repurpose expired Loperamide, a widely available antidiarrheal drug, as a green corrosion inhibitor, demonstrating a novel way to reduce pharmaceutical waste product while promoting circular-economy practices. In this study, expired Loperamide—an electroactive organic compound containing nitrogen and oxygen heteroatoms capable of donating electrons has been investigated as a corrosion inhibitor for mild steel, a commonly used industrial material in 0.5 M HCl solution selected to simulate acidic cleaning and pickling environments. Its performance was evaluated using gravimetric analysis, electrochemical techniques, quantum chemical calculations, and surface characterization (SEM and EDS). Gravimetric measurements at a concentration of 2500 mg/L revealed 88.65% inhibition efficiency. Electrochemical results verified the inhibitor's effectiveness, with potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) of 88.19% and 92.09% efficiencies, respectively. The observed inhibition obtained from adsorption of Loperamide molecules on the steel surface, forming a protective barrier that impedes metal dissolution. This approach not only offers a cost-effective and environmentally compatible solution but also promotes the reuse of pharmaceutical waste, supporting green economy principles and sustainability in corrosion control.
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© The Author(s), under exclusive licence to Società Italiana di Fisica and Springer-Verlag GmbH Germany, part of Springer Nature 2025
Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.
