DFT and experimental studies on the inhibition potentials of expired Tramadol drug on mild steel corrosion in hydrochloric acid

The effectiveness of expired Tramadol (ETr) as a corrosion inhibitor for mild steel in 1 M HCl solution was tested by electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PDP), surface analysis (SEM and AFM), and density functional theory (DFT) methods The data obtained from EIS and PDP curve indicated the inhibition efficiency is in direct relationship to Tramadol concentration. The Langmuir adsorption isotherm data confirms a physiochemical mechanism. The SEM and AFM analyses reveal a smoother surface of mild steel. The DFT calculations were used to evaluate the electronic parameters of the neutral and protonated forms of the drug.