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International Journal of Corrosion
Volume 2010 (2010), Article ID 275983, 10 pages
Research Article

Aqueous Extract of Kalmegh (Andrographis paniculata) Leaves as Green Inhibitor for Mild Steel in Hydrochloric Acid Solution

1Department of Chemistry, Udai Pratap Autonomous College, Varanasi 221002, India
2Department of Applied Chemistry, Institute of Technology, Banaras Hindu University, Varanasi 221005, India

Received 10 May 2010; Revised 15 June 2010; Accepted 23 June 2010

Academic Editor: Ravin Kumar Dayal

Copyright © 2010 Ambrish Singh et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


The inhibition of the corrosion of mild steel in hydrochloric acid solution by the extract of Kalmegh (Andrographis paniculata) leaves extract has been studied using weight loss, electrochemical impedance spectroscopy, linear polarization, and potentiodynamic polarization techniques. Inhibition was found to increase with increasing concentration of the extract. The effect of temperature, immersion time, and acid concentration on the corrosion behavior of mild steel in 1 M HCl with addition of extract was also studied. The inhibition was assumed to occur via adsorption of the inhibitor molecules on the metal surface. The adsorption of the molecules of the extract on the mild steel surface obeyed the Langmuir adsorption isotherm. The protective film formed on the metal surface was analyzed by FTIR spectroscopy. The results obtained showed that the extract of Kalmegh (Andrographis paniculata) leaves extract could serve as an effective inhibitor of the corrosion of mild steel in hydrochloric acid media.