Electrochemical and computational examination on adsorption and protection of copper in 1 M HCl by expired biguanide drug

• K. EL Mouaden¹, D.S. Chauhan^2,3, A. Saket², S. Yadav^2,3, L. Bazzi⁴, H. Ahchouch⁵, R. Salghi⁵ and M.A. Quraishi³

¹ Applied Chemistry-Physics Team, Faculty of Sciences, Ibn Zohr University, B.P.8106 Cité Dakhla, Agadir, Morocco
² Department of Chemistry, Faculty of Basic Science, AKS University, Satna, Madhya Pradesh, 485001, India
³ Centre for Green Chemistry and Sustainability, AKS University, Satna, Madhya Pradesh 485001, India
⁴ Industrial and logistic laboratory, Sup MTI Rabat, Morocco
⁵ Laboratory of Applied Chemistry and Environment, ENSA, Ibn Zohr University, PO Box 1136, 80000 Agadir, Morocco

Abstract: The utilization of expired pharmaceuticals as corrosion inhibitors has gained importance in recent years. Herein, for the first time, expired drug Biguanide (BGD) was evaluated as a green corrosion inhibitor for copper in 1 M HCl solution, employing electrochemical and surface analytical techniques. This is the first investigation on the application of an expired drug as a corrosion inhibitor for the Cu surface in 1 M HCl. The adsorption of the drug on the metallic substrate was in agreement with the Langmuir isotherm. Maximum efficiency of 88.6% was achieved by the drug with a mainly physical model of adsorption. An increase in the protective performance was noticed with the inhibitor dose. Electrochemical impedance spectroscopy (EIS) indicated a charge transfer-controlled mechanism of the inhibitor on the Cu surface, while the potentiodynamic polarization (PDP) study evidenced a mixed type of behavior. Cyclic voltammetry measurements evidenced that the inhibitor significantly affected the redox process of Cu corrosion. SEM analysis revealed the appearance of a smooth surface morphology of the Cu substrate in the presence of the inhibitor. Computational studies revealed that the inhibitor undergoes protonation in the acidic solution. The protonated form of the inhibitor shows greater reactivity compared to the neutral form. The obtained results provide support for the potential application of the drug BGD in the industrial acid-pickling process.

Keywords: green chemistry, corrosion inhibitors, expired drugs, biguanide, copper corrosion

Int. J. Corros. Scale Inhib., 2026, 15, no. 3, 520-542
doi: 10.17675/2305-6894-2026-15-3-23

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