Electrochemical and surface study of an antibiotic drug as sustainable corrosion inhibitor on mild steel in 0.5 M H2SO4

Corrosive degradation of mild steel using the antibiotic ethambutol hydrochloride drug as a sustainable inhibitor in 0.5 M sulphuric acid was studied and found as an efficient inhibitor. The inhibitive action showed an increase with an upsurge in the drug concentration, but with escalating temperature, inhibition efficiency declined. The drug showed a best of 92.78% inhibition efficiency at 1000 ppm and 313 K. The thermodynamic, kinetic and adsorption parameters were evaluated and established the physisorption of the drug over the metal surface following Langmuir adsorption isotherm. The EIS analysis confirmed the adsorption of inhibitor on the metal surface by showing the lowering in the value of double layer capacitance, Cdl; improvement in charge transfer resistance, Rct as the surface modulus raised. The mixed type of inhibition mechanism was confirmed by a Potentiodynamic polarization experiment. Surface morphology through Atomic Force Microscopy (AFM) validated the less deteriorated metal surface exposed to corrosive medium in presence of the drug.