Allium sativum as Corrosion Inhibitor for Carbon Steel in Sulfuric Acid

A study on the use of Allium sativum (garlic) as corrosion inhibitor for carbon steel in 0.5M H2SO4 has been carried out by using potentiodynamic polarization curves, electrochemical impedance spectroscopy and weight loss measurements. Inhibitor concentrations included 0, 100, 200, 400, 600 and 800 ppm at 25, 40 and 600C. Allium sativum has been proved to be good inhibitor, reaching its highest efficiency, 96%, with the addition of 400 ppm. This reduction in the corrosion rate was due to the formation of an external layer formed by S-containing film present in the extract which was adsorbed physically on the steel surface. Allium sativum acted as a mixed type of inhibitor.