Corrosion inhibition of mild steel in hydrochloric acid using extract of glycine max leaves

The activity of glycine max leaves extract against corrosion of mild steel in 0.5 M HCl solution has been investigated at different temperatures (298-328 K). Different measurements were done using weight loss, Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM)-energy dispersive x-ray spectroscopy (EDS) and X-ray diffraction (XRD) techniques. The weight loss results indicate that glycine max leaves extract is a good inhibitor and its optimum inhibition efficiency reaches up to 91.07 % at 2 g l(-1) (308 K). The adsorption of the inhibitor molecules onto the mild steel surface was found to follow the Langmuir adsorption isotherm. The values of the Gibbs free energy of adsorption strongly support physisorption of inhibitor molecules on the mild steel surface. The decrease in inhibition efficiency is observed with increasing temperature, but increases with increase in inhibitor concentration. Formation of a protective layer against acid attack on the metal surface was confirmed by use of FT-IR, XRD analysis, and SEM.