Use of Warfarin as corrosion inhibitor for carbon steel in saline solution

• H.H. Hameed and Z.W. Ahmed

Department of Chemistry, College of Education for Pure Science (Ibn Al-Haitham), University of Baghdad, Antar Square, Street 20, Al-Adhamiya District, 10053 Baghdad, Iraq

Abstract: Unused and expired pharmaceutical drugs represent an innovative type of organic corrosion inhibitor because of their distinctive properties. They are less expensive, more effective, and less harmful than conventional organic corrosion inhibitors. This study investigated the effect of expired Warfarin as a corrosion inhibitor for carbon steel in a saline solution (3.5% NaCl). The polarization method was used to determine the corrosion rate and inhibition efficiency. The results showed that the inhibition efficacy (IE%) reached 92% at 293 K in the presence of 0.1 g/L Warfarin. The results also revealed that inhibitor molecules adsorb onto carbon steel surfaces through physical adsorption, as evidenced by the levels and signs of the Gibb adsorption free energy. It was discovered that the adsorption of the medicine onto the surface of carbon steel occurs naturally and follows the Langmuir adsorption isotherm mode. We determined that the adsorption of pharmaceutical on the carbon steel surface occurred naturally by fitting experimental data to the Langmuir adsorption isotherm. This led us to the conclusion that the adsorption of the medication was spontaneous. The apparent activation energies (E_a^*) of the inhibited process were higher compared to the uninhibited process at all concentrations. SEM analysis showed a significant reduction in the corrosion of carbon steel in 3.5% NaCl inhibited by Warfarin compared with uninhibited saline solution.

Keywords: expired Warfarin, carbon steel, thermodynamic parameters, Langmuir

Int. J. Corros. Scale Inhib., 2026, 15, no. 2, 128-142
doi: 10.17675/2305-6894-2026-15-2-8

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