Inhibitory action of Vernonia amygdalina extract (VAE) on the corrosion of carbon steel in acidic medium

Olawale, Olamide ; Adediran, Adeolu Adesoji ; Talabi, Segun Isaac ; Nwokocha, Geraldine Chika ; Ameh, Alewo Opuada (2017)


This study investigates the inhibition potential of Vernonia amygdalina stem extract (VAE) on the corrosion of mild carbon steel immersed in 1 M HCl solution containing various concentrations of the inhibitor. The corrosion rate and inhibition efficiency were evaluated using mass loss and adsorption techniques. The results revealed that VAE efficiently inhibits the corrosion rate of mild carbon steel immersed in the acidic medium. The concentration of 0.6 g/L provides the highest inhibition efficiency of 78.1 %. The adsorption process was consistent with the physisorption mechanism and obeyed the Langmuir isotherm. The functional groups responsible for inhibition were identified using Fourier Transform Infrared (FTIR) spectra. The surface morphology of the corroded samples examined with Scanning Electron Microscope (SEM) revealed the presence of protective oxide layer. Inhibition efficiency was found depended on the presence of oxalate, phytate, tannins, saponins and flavonoids in the VAE. It has been concluded that VAE is safe, cheap and efficient corrosion inhibitor for mild carbon steel.