Inhibition by Newbouldia leavis Leaf Extract of the Corrosion of Aluminium in HCl and H2SO4 Solutions

The inhibition effect of Newbouldia leavis leaves extract on the corrosion of aluminium in 0.2- 1.0 M HCl and 0.1–1.0 M H2SO4 solutions was investigated by the gravimetric technique. The results show that Newbouldia leavis is a good inhibitor, and exhibits more efficient in 1.0 M HCl than 0.5 M H2SO4. It was shown that the presence of Newbouldia leavis leaf extract inhibited the corrosion of aluminium in the test solutions and the inhibition efficiency depended on the concentration of the plant extract as well as on the time of exposure of the aluminium samples in H2SO4 solutions containing the extract. The experimental data complied to the Langmuir 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 aluminium surface through a physical adsorption mechanism. The adsorption of Newbouldia leavis on aluminium surface obeys Langmuir adsorption isotherm.