The unused expired clinical drugs are a major environmental hazardous pollutant due to the pharmaceutically active organic compounds present in it. Until recently, a quantum of unused drugs is being disposed through sewers, drainage, sediment are a threat to the public health. Several researchers have already reported the potential use of expired drugs as corrosion inhibitors in both acidic and alkaline medium. In this paper, we have reported three different drug molecules which have crossed the expiry date but not beyond six months. The drugs considered are rabeprazolesodium, domperidone and benfotiamine. Mild steel (MS) specimens were immersed 5 days with and without drug molecule in 3.5 wt% medium film formed on MS surface. These films were then analysed for crystallinity, surface morphology, iron complex, DFT and functional groups by XRD, SEM, and 3D profilometer, FTIR, UV and EPR. The experimental and theoretical results are good agreement with each other.