Expired Indomethacin Therapeutics as Corrosion Inhibitors for Carbon Steel in 1.0 M Hydrochloric Acid Media

Indomethacin in the form of expired drugs which have low price was used as corrosion inhibitor for carbon steel in 1.0 M HCl solution using chemical and electrochemical techniques, namely, weight loss, electrochemical impedance spectroscopy (EIS), potentiodynamic polarization, and scanning electron microscopy (SEM). Inhibition efficiency increased with increasing inhibitor concentrations and decrease by temperature. The Results show that expired indocin capsules is a good inhibitor where the inhibition efficiency reaches 83% at 500 ppm of the used inhibitors. Data obtained from EIS studies were analyzed to model the corrosion inhibition process through appropriate equivalent circuit models. The adsorption of indocin drugs obeyed Langmuir adsorption isotherm. The thermodynamic parameters were calculated and discussed. Polarization curves indicated that they are mixed type of the inhibitors. SEM was used to study the surface morphology of the steel in the absence and presence of the additive. The results obtained from weight loss, EIS, and Potentiodynamic polarization are in good agreement and show that the expired drugs of many advantages like low price, save, and high availability act as eco-friendly corrosion inhibitor for steel