Expired flunarizine hydrochloride as corrosion inhibitors for Q235 steel in hydrochloric acid medium: Experimental and computational investigation

Abstract

The corrosion of carbon steel is always a very serious issue, and the addition of corrosion inhibitors is an effective approach to prohibiting the corrosion of carbon steel. Because expired drugs are environmentally friendly, green, and non‐toxic; thus, this work provides a new idea for the treatment of expired drugs. The expired flunarizine hydrochloride (FH) is used as corrosion inhibitors for Q235 steel, investigating the corrosion inhibition efficiency of expired FH with different concentrations for carbon steel and illustrating the corrosion inhibition mechanism. Electrochemical impedance and Tafel curves are used to investigate the corrosion inhibition of carbon steel under 1 M HCl solution with different concentrations of the expired FH, and the corrosion efficiency is calculated according to the immersion tests, and the corrosion inhibition efficiency is more than 88.5%. Scanning electron microscopy (SEM), Fourier transform infrared spectrometer (FTIR), and Raman spectroscopy strongly support the results of the electrochemical experiment. Besides, the simulation results also provide the strong supports for the experimental results.