The inhibition potentials of expired glibenclamide (Glib) and glimepiride (Glim) as two significantsulfonylurea antibiotic drugs on the corrosion behavior of mild steel in 0.5 M sulfuric acid solution wereexplored using different chemical and electrochemical ways. As the concentration of the expired drugsincreases, the weight loss, corrosion current density and the capacity of double layer decrease while thevalues of charge transfer resistance, surface coverage and the percentage inhibition efficiency augment,indicating that the inhibitory impact of both expired Glib and Glim. The percentage inhibition efficiencyincreases with decrease in temperature. The inhibition was interpreted by the spontaneous adsorption ofthe two expired drugs on the mild steel surface by increasing the number of adsorbed particles that coverthe largest area of the metal by constructing a barrier layer between the steel surface and the corrosiveacid solution. The adsorption process is subject to Langmuir isotherm. Potentiodynamic polarizationdata demonstrate that both expired drugs act as mixed inhibitors. The activation and adsorptionthermodynamic parameters were evaluated and suggest the physical adsorption of the examined drugs.
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