Adsorption and corrosion inhibition of Osmanthus fragran leaves extract on carbon steel

► Osmanthus fragran leaves extract acted as a highly efficient inhibitor for C-steel. ► The adsorption of the inhibitor obeyed Langmuir adsorption isotherm. ► The adsorption was a spontaneous, exothermic process with an increase in entropy. ► AFM and FTIR results confirmed the inhibition effect of the inhibitor. ► Quantum chemical calculations provided reasonable theoretical explanation. The adsorption and corrosion inhibition of Osmanthus fragran leaves extract (OFLE) on C-steel in hydrochloric acid was investigated by potentiodynamic polarisation, electrochemical impedance spectroscopy (EIS), atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR) and quantum chemical calculations. OFLE acted as a highly efficient mixed type inhibitor. The adsorption of OFLE on the C-steel surface obeyed Langmuir adsorption isotherm. The calculated adsorption thermodynamic parameters indicated that the adsorption was a spontaneous, exothermic process accompanied by an increase in entropy. Quantum chemical parameters were also calculated, which provided reasonable theoretical explanation for the adsorption and inhibition behaviour of OFLE on C-steel.