Table of Contents
ISRN Corrosion
Volume 2013, Article ID 895120, 7 pages
http://dx.doi.org/10.1155/2013/895120
Research Article

Effect of Serine and Methionine on Electrochemical Behavior of the Corrosion of Mild Steel in Aqueous Solutions

1Chemistry Department, Faculty of Science, Benghazi University, P.O. Box 1308, Benghazi, Libya
2Chemistry Department, Faculty of Science, AL Azhar University, Cairo, Egypt
3Chemistry Department, Faculty of Arts and Sciences, Benghazi University, Kufra, Benghazi, Libya

Received 9 December 2012; Accepted 30 December 2012

Academic Editors: N. Boshkov and Q. Qu

Copyright © 2013 Mohamed N. Rahuma 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.

Abstract

The pitting corrosion behaviour of mild steel in Na2HPO4 solutions contains chloride ion as an aggressive ion and serine and methionine as inhibitors were investigated using open-circuit potential (OCP), potentiodynamic polarization measurements, and pitting corrosion current measurements; both inhibitors shift the potential in the positive direction. The corrosion rate of the mild steel was measured in the absence and presence of the inhibitors, and the inhibition efficiency of the amino acids at a concentration of 0.02 M was calculated. The pitting corrosion current shows that increasing concentration of the inhibitor causes a decrease in pitting current density, and inhibition efficiency increases with increasing concentration of the inhibitors. The adsorption of these inhibitors on the mild steel surface obeys Langmuir isotherm, and the calculated adsorption free energy (Δ) for the inhibitors on the mild steel in 0.1 M (Na2HPO4 + NaCl) solutions was found to be (−24.61, −29.34) kJ/mol for serine and methionine, respectively, which reveals strong physical adsorption of the amino acids molecules on the mild steel surface.