The inhibitory action of expired asthalin drug on the corrosion of mild steel in acidic media: A comparative study

Abstract

A comparative study of expired asthalin drug was studied for its inhibitive effect on mild steel in 1M HCl and 1M H2SO4 medium, using the metrics of weight loss and electrochemical techniques. The various parameters such as corrosion rate, inhibition efficiency and surface coverage were calculated. The weight loss method shows that the inhibition efficiency increases with the increase of inhibitor concentration, time and temperature. A mixed mode of inhibition mechanism was proposed for the effect of examined asthalin drug, as revealed by potentiodynamic polarization technique. Thermodynamic parameter such as free energy value was negative, that indicates spontaneous adsorption of inhibitor on mild steel surface. The nature of adsorption of the inhibitor on the mild steel surface was in conformity with Langmuir adsorption isotherm. The surface morphology of the mild steel, with and without the inhibitor, was studied using scanning electron microscopy (SEM).