Donepezil Drug as a Potential Inhibitor for the Corrosion Mitigation of EN24 Steel in Sulfamic Acid Medium: Electrochemical and Theoretical Investigation

Abstract In the present study corrosion inhibition behaviour of Donepezil (DPZ), an environmentally friendly pharmaceutical drug, on EN24 steel in 0.5 M sulfamic acid (NH 2 SO 3 H) medium was investigated using electrochemical methods. DPZ exhibited an optimum inhibition efficiency of 77.66% at 1 × 10 − 3 M. Impedance analysis indicated an enhance in the resistance towards the charge transfer process. Potentiodynamic polarization results demonstrated that DPZ functioned as mixed-type inhibitor with a slightly stronger influence on cathodic reaction and significantly reduced the corrosion current density with increase in DPZ concentration. The adsorption of DPZ on the EN24 surface followed Langmuir model, showing a mixed type of adsorption. Density Functional Theory (DFT) calculations, supported by Molecular Electrostatic Potential (MEP) mapping and topology analyses, provided theoretical support to the experimental observations. The surface analysis using Scanning Electron Microscopy (SEM), Energy Dispersive X-ray ( EDX) and Atomic Force Microscopy (AFM) substantiated the adsorption of the DPZ molecules onto the EN24 steel surface. Graphical Abstract