Expired Dexon Drug as Green Inhibitor for Carbon Steel in Simulated Seawater Medium

The addition of expired drugs as green inhibitors takes high attention as an alternative material compared with other expensive, toxic, non-available chemical inhibitors. In this study, the Dexon drug was suggested as a green inhibitor for commonly used carbon steel in (3.5% NaCl solution) within a temperature range of 303 to 333 K. Corrosion/inhibition investigation was done by potentiostatic analysis to record the corrosion potential, corrosion current density, and Tafel slopes for the added four concentrations (4, 20, 40 and 60 mL/L) of the drug. The polarization resistances and inhibition efficiencies reached the highest value of (25.86×10-3 Ω.cm2) and (95.57%) respectively for 60 mL/L at 303 K. For examination of inhibited surface, Infrared spectrum, electron scanning microscopy, and atomic force microscopy. These techniques confirmed effective surface coverage by the adsorbed drug, forming a (Fe²⁺ ‒ Dexamethasone) complex. This was further supported by a reduction in surface roughness from 270.8 nm to 24.96 nm following inhibition using a concentration of 60 mL/L. Theoretical calculations indicated that the adsorption process was physical, spontaneous, less disordered, and exothermic. Additionally, quantum data, including HOMO and LUMO analyses, demonstrated the high adsorption capability of the Dexamethasone molecule on the steel surface. The results showed an energy gap of 3.43 eV, reflecting the molecule’s soft nature and the release of energy during the adsorption process.