A Case Study on Expired Drugs : The Potential Corrosion Inhibitory Activity of Expired Labetalol Drug in 1M HCl for Plain Carbon Steel

In this work expired drug namely, labetalol has been used as a corrosion inhibitor in a stirred acidic medium (1M HCl) with mass loss measurement and electro analytical techniques. The efficiency of the inhibitor increases as the temperature increases from 30-60°C. The results reveal that maximum inhibition efficiency is observed as 91.66% for 500 ppm. Potentiodynamic polarization measurement implies that it perform as a mixed type inhibitor. FT-IR analysis prove that corrosion product is formed on the mild steel surface. When compared with metal in IM HCl, it includes a shielding layer on the surface of mild steel by controlling further attack of acid. SEM and SFM surface morphology study have also been performed to confirm the effect of labetalol on metal. In addition to that, DFT is also carried out to analyse HOMO, LUMO, ΔE and Mulliken charges.