Comparative Study of Mild Steel Corrosion Inhibition of Piper Guineense Leaves Extract and Vernonia Amygdalina Leaves Extract in Concentrated Corrosive Medium

The inhibitory behavior of Piper guineense leaves extract and Vernonia amygdalina leaves extract on corrosion of mild steel in 2.5M HCl solution, are comparatively studied using gravimetrical and gasometrical methods respectively. The results obtained showed that both Piper guineense leaves extract and Vernonia amygdalina leaves extract efficiently inhibit corrosion of mild steel in concentrated corrosive medium. The inhibition efficiency increased with increase in the extract concentration but decreased with rise in temperature. Both plant extracts showed almost 100% inhibition efficiency at concentration of 0.5g/l. The corrosion inhibition properties of the two plant extracts is attributed to adsorption of the phytochemical molecules on the surface of the mild steel creating a barrier between the mild steel and the corrosive solution, and the adsorption of the extracts fitted into Langmuir adsorption isotherm. A study of the trends in thermodynamic parameters like activation energy and heat of adsorption indicated that both Piper guineense leaves and Vernonia amygdalina leaves extracts were physically adsorbed to the metal surface, and the reaction was spontaneous and exothermic.