An expired pharmaceutical product, Carvedilol, was studied as save drug to prevent carbon steel (CS) corrosion in acidic environments by using weight loss, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and electrochemical frequency modulation (EFM) techniques. The inhibition efficiency increased with increasing drug dose and decreased with increasing temperature, reaching a maximum value of 98.94% at 25°C and 1.6 × 10 −4 M. Polarization data showed that the drug is of a mixed type. The inhibition of CS corrosion by Carvedilol can be attributed to the adsorption ability of drug molecules onto the reactive sites of the metal surface. The adsorption process follows the Langmuir isotherm via physical adsorption. The surface morphologies of CS were examined by atomic force spectroscopy (AFM). The results obtained from different techniques are in good agreement.