Inhibitive Action and Adsorption Characteristics of Alternanthera bettzickiana Extracts on the Corrosion of Mild Steel in Acidic Media

The inhibitive action of leaves, stem and root extracts of Alternanthera bettzickiana on mild steel corrosion in 5 M H2SO4 solutions was studied using gravimetric technique in the temperature range 30°C to 60°C. Maximum inhibition efficiency (and surface coverage) was obtained at an optimum concentration. However, increase in temperature decreased the inhibition efficiency at the temperature range studied. The experimental data complied with the Langmuir, Freundlich and Temkin adsorption isotherm and the value and sign of the Gibb’s free energy of adsorption obtained suggested that inhibitor molecules have been spontaneously adsorbed onto the mild steel surface through a physical adsorption mechanism. Thermodynamic parameters revealed that the adsorption process is spontaneous.