Using expired pharmaceutical Clotrimazole as a corrosion inhibitor for stainless steel in acidic media

• H.A. Almashhadani

Department of Chemistry, College of Science, University of Baghdad, 10011, Baghdad, Iraq

Abstract: In this work, the effect of expired/unused Clotrimazole drug (ECD) on the corrosion tendency of stainless steel 316 (SS316) in acidic media (0.1 M HCl) at temperatures ranging from 298 to 328 K has been studied. The potentiodynamic polarization (PDP) technique was used to investigate the corrosion inhibition efficiency (IE%) of ECD adsorption on SS316 at various concentrations. Atomic Force Microscopy (AFM) technique was used to examine the surface morphology of corroded SS316 with and without inhibition of the acidic solution by ECD. Fourier Transform infrared spectroscopy (FTIR) was used to confirm the ECD adsorption on the surface of SS316. The results demonstrated that the inhibition efficiency rose as the ECD concentration increased, while it decreased as the temperature increased. The inhibition performance reached 99% with 100 ppm at 298 K. The corroded SS316 surface was studied by AFM to confirm the adsorption of ECD on the metal surface. Corrosion current densities at various temperatures were utilized to estimate the apparent activation energy (E_a), activation enthalpy (ΔH*), and activation entropy (ΔS*). The apparent activation energy increased upon addition of the inhibitor from 19.99 kJ·mol^–1 to 70.39 kJ·mol^–1 at 100 ppm of ECD, indicating its effectiveness in inhibiting the corrosive media. The ΔH* values were positive and increased upon inhibition of the corrosive media by ECD.

Keywords: corrosion inhibitor, Clotrimazole, stainless steel, expired drug

Int. J. Corros. Scale Inhib., 2024, 13, no. 3, 1636-1648
doi: 10.17675/2305-6894-2024-13-3-15

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