Electrochemical and Thermodynamic Study of Septrin and Flagyl as Corrosion Inhibitors for Mild Steel in Acidic Media

Corrosion of mild steel in acidic media is a significant issue in industrial applications, leading to material degradation and increased maintenance costs.This study investigates the corrosion inhibition properties of Septrin (Co-trimoxazole) and Flagyl (Metronidazole) for mild steel in 2 M HCl, with the aim of finding alternative, cost-effective inhibitors.These drugs were selected due to their potential anticorrosion properties, with limited research available on their inhibitory efficiency in acidic environments.The study was conducted over a temperature range of 303 K to 363 K, with inhibitor concentrations varying from 25 g/L to 75 g/L.Both drugs exhibited promising corrosion inhibition, with Flagyl showing superior performance.The adsorption of both inhibitors followed the Langmuir and Freundlich isotherms, indicating a physisorption mechanism.Gibbs free energy calculations confirmed the spontaneity and stability of the adsorption process, with Septrin showing G_ads values of -19.13 kJ/mol at 303 K and -22.91 kJ/mol at 363 K, while kJ/mol at 363 K. Electrochemical tests revealed that Flagyl reduced the corrosion rate from 149.35 mm/year to 60.02 mm/year at a concentration of 75 g/L, while Septrin reduced it to 78.53 mm/year, resulting in inhibition efficiencies of 59.8% and 47.4%, respectively.Thermodynamic analyses indicated an increase in activation energy in the presence of both inhibitors.Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray (EDX) analyses showed that both inhibitors improved the surface conditions of mild steel, with Flagyl being the more effective inhibitor.Future research should focus on evaluating the longterm stability of these inhibitors in corrosive environments.