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ISRN Corrosion
Volume 2012 (2012), Article ID 819719, 10 pages
Research Article

Chemical Degradation of Epoxy-Polyamide Primer by Electrochemical Impedance Spectroscopy

Department of Chemistry, College of Science, Eritrea Institute of Technology, Mai Nefhi, Asmara, Eritrea

Received 24 February 2012; Accepted 10 April 2012

Academic Editors: K. N. Allahar, G. Bereket, C. V. D'Alkaine, and R. Salghi

Copyright © 2012 Ramesh Duraisamy 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 degradation of organic-inorganic hybrid materials based on epoxy resin was characterized electrochemically in aggressive chemical electrolyte. In the present study, the hybrid material as primer was prepared from epoxy resin pigmented by zinc phosphate cured with polyamide (EPZ). The hybrid material was coated on mild steel substrate, and the corrosion behavior was studied by electrode-potential time measurements and mainly by electrochemical impedance spectroscopy (EIS) in 5% NaCl solution. The impedance parameters, namely, coating capacitance ( 𝐢 𝑐 ), pore resistance ( 𝑅 p o ), charge transfer resistance ( 𝑅 𝑑 ), double layer capacitance ( 𝐢 d 1 ), and break point frequency ( 𝑓 𝑏 ), corresponding to 45° phase angle as a function of time of exposure were estimated. The observed impedance behavior were compared with the established equivalent electrical circuit represents the coated metal/electrolyte interface. Changes in the values of the circuit components given the information on the stages of degradation and physical phenomenon occurring throughout the degradation of primer coating were also been predicted. In addition, information related to the porous nature of the primer, limited passivation effect, and delamination of coating with longer exposure that resulted in the diffusion controlled corrosion of metal are also recognized. Thus, results indicate that the EPZ coating had good corrosion resistance. This could be a nonpolluting alternative to the traditional chromate like environmentally harmful coatings.