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E-Journal of Chemistry
Volume 9 (2012), Issue 4, Pages 1746-1752
http://dx.doi.org/10.1155/2012/368147

Synergistic and Antagonistic Effects of Sodium Molybdate-Zn2+ System

1Department of Chemistry, Jeppiaar Engineering College, Chennai - 600 119, India
2Department of Chemistry, Peiryar E.V.R. College, Trichy, Tamil Nadu, India
3Department of Chemistry, RVS School of Engineering and Technology, Tamil Nadu, India
4Corrosion Research Centre, Post Graduate and Research, Department of Chemistry, GTN Arts College, Dindigul-624 005,Tamil Nadu, India
5Department of Chemistry, Vellalar College for Women, Erode, India

Received 18 August 2011; Revised 5 November 2011; Accepted 9 November 2011

Copyright © 2012 Hindawi Publishing Corporation. 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 inhibition efficiency (IE) of sodium molybdate (SM) in controlling corrosion of carbon steel in an aqueous solution containing 120 ppm of Cl-, in the absence and presence of Zn2+ has been evaluated by weight-loss method. A synergistic effect exists between SM and Zn2+ when the concentration of Zn2+ is 25 ppm and above. Inhibition efficiencies obtained are greater than 85%. Antagonistic effect exists between SM and Zn2+ when the concentration of Zn2+ is 10 ppm and below. The SM-Zn2+ system shows excellent IE up to third day. Above third day IE decreases. Acceleration of corrosion takes place. Excellent IE is shown at pH 5,7 and 12. At pH 9, IE decreases since Zn2+ is precipitated as Zn(OH)2 in the bulk of the solution. Polarization study reveals that SM-Zn2+ system functions as a mixed inhibitor. FTIR spectra reveal that the protective film consists of Fe2+-SM complex and Zn(OH)2.