Effect of Aqueous Extracts of Leaves, Stem and Seed of Azadirachta indica on Corrosion Inhibition of Mild Steels in Acidic Medium

Abstract

The application of aqueous extracts of leaves, stem and seed of Azadirachta indica as good green corrosion inhibitors of mild steels in 0.25 M hydrochloric acid (HCL) was evaluated. Extracts were prepared by evaporating the filtrate of the aqueous solution obtained from dried samples, hence, used for the preparation of inhibitor test solutions. Mild steel rods of 8 mm diameter were used. Phytochemical screening of aqueous leaf, stem and seed extracts of Azadirachta indica (Neem) and corrosion inhibition rates of the extracts in 0.25 M HCl were determined by gravimetric analysis. The weight loss was calculated after each measurement, the inhibitory efficiency (I%), corrosion rate (Cr) and surface coverage (θ) were calculated using mathematical relationships. The mechanism of inhibitor adsorption on the metal steel surface was studied using Langmuir adsorption isotherms. The results revealed that extracts of leaves, stem and seed of Azadirachta indica were effective at inhibiting the rate of corrosion on the mild steels in 0.25 M HCl medium. The effectiveness of the extracts as corrosion inhibitors was observed to be dependent on the concentration of the extracts. The extracts were most effective after 9 days exposure period with inhibition efficiencies of 94.22 % (leaves), 86.27 % (stem), 83.22 % (seed) at 1.0 g concentration, while at the end of the 15 days exposure period, 1.0 g concentration of the extracts produced the highest inhibition efficiency at 94.17 %, 86.18 % and 83.11 % for the leaves, stem and seed extracts respectively. The Langmuir isotherm was obeyed by the extracts. The findings of this study demonstrated that neem leaves, stem and seed aqueous extracts are good green corrosion inhibitors therefore, their use as corrosion inhibitors should be greatly encouraged.