Expired Lorazepam Drug: A Medicinal Compound as Green Corrosion Inhibitor for Mild Steel in Hydrochloric Acid System

The present study explores the green corrosion inhibition property of expired Lorazepam tablet on the mild steel (MS) in 3M HCl solution using gravimetric (mass loss), atomic absorption, Tafel plot, electrochemical impedance, quantum chemical, and scanning electron microscopy (SEM) studies. It is found that; expired Lorazepam tablet shows the robust corrosion inhibition property (protection efficiency = 90%) on the MS at 0.4 g/L of expired Lorazepam drug (observed from the gravimetric studies) at 333 K with a contact time of 3 h. The significant enhancement in the protection performance of the expired Lorazepam tablet has been observed by atomic absorption spectroscopy technique. The results of Tafel plots show that, the presence of the expired Lorazepam tablet of different concentration decreases the both cathodic and anodic processes at MS in the 3M HCl solution by blocking the MS active sites and behave as a mixed mode corrosion inhibitor. Electrochemical impedance studies show that, increase in the amounts of expired Lorazepam tablet increases the charge transfer process at MS-HCl interface. The electron transfer nature of the expired Lorazepam tablet on the MS surface was confirmed from the Quantum chemical studies. The adsorbed invisible layer over the surface of MS was scrutinized by scanning electron microscopy technique.