Materials Sciences and Applications, 2012, 3, 348-354 http://dx.doi.org/10.4236/msa.2012.36050 Published Online June 2012 (http://www.SciRP.org/journal/msa) Electrochemical Behavior and Corrosion Study of Electrodeposits of Zn and Zn-Fe-Co on Steel Conceição A. M. Dutra * , Eduardo N. Codaro, Roberto Z. Nakazato Departamento de Física e Química, Universidade Estadual Paulista, Campus de Guaratinguetá, Guaratinguetá, Brazil. Email: * conmat@feg.unesp.br Received March 21 st , 2012; revised April 25 th , 2012; accepted May 26 th , 2012 ABSTRACT From industrialized baths, free of cyanide, the corrosion behavior of electrodeposits of zinc and zinc alloys was studied by means of electrochemical tests in aerated solution of 3.5% (0.6 M) NaCl at pH 8.2. In literature, several studies are found about zinc coatings and zinc alloys, for example, Zn-Ni and Zn-Co, nevertheless there is little about the ternary alloy Zn-Fe-Co. The Fe presence in the alloy results in a good adhesion to the substrate and allows application of these materials at higher temperatures. The electrochemical tests were carried out by obtaining open circuit potential curves with immersion time, potentiodynamic polarization curves and cyclic voltammetry. From the obtained results, the large potential differences observed between the steel and the electrodeposits showed that the last protect the substrate, acting as a sacrifice metal. The tests disclosed similar behaviors in both the current densities and the corrosion potential for electrodeposits of Zn and Zn-Fe-Co. After chromate passivation process, a significant decrease in corrosion density was noted for Zn and when the system was de-aerated there was change in the cathodic process mechanism. Keywords: Corrosion; Electrodeposition; Zn; Zn Alloy 1. Introduction Zinc gives galvanic protection to steel by presenting a good accomplishment in most atmospheric conditions and also good mechanical and corrosive characteristics. In relation to electrogalvanised layers, zinc alloys have been commonly more used due to their low cost and their re- sistance to the corrosion process, which can triple, mak- ing them significantly more efficient [1]. Zinc electrode- position with metals of Fe group, besides cost advantage, it is classified as anomalous [2]; these coatings present protection mechanisms by barrier associated with ca- thodic protection [3,4]. The increasing use in the industries has caused a great progress in technology of coatings based on zinc. In re- cent years, particularly in automotive industry, it has increased the requirements and the demand of coatings, which are alternative to zinc and cadmium for steel pro- tection. It has resulted in the development of zinc alloys with metals of group VIII B, such alloys present superior properties of corrosion resistance and low toxicity. Fur- thermore, characteristics of these coatings can be im- proved by post-treatment. Chemical conversion processes with chromates are widely applied in metals passivation. Chromatization is used as a more effective inhibiting process, although the hexavalent chromium presents very toxic effects. As a result, oxy-anions similar to chromate, such as molybdate, tungstate and vanadate, are studied as alternatives. The objective of this paper is to study the electrochemical behavior of Zn and Zn-Fe-Co electrodeposits upon steel in 3.5% NaCl, by analyzing the addition effect of 2 4 CrO  , 2 4 MoO  and 2 4 WO  0.05 M. 2. Materials and Methods Using as substrate SAE 1010 steel plates 0.75 mm thick, the working electrode was prepared with pure Zn elec- trodeposits (NCZ ZINCROLYTE 191  ) and Zn-Fe-Co (NCZ ZINCROLYTE 191 Fe/Co  ) in commercial baths based on chlorides, cyanide-free and industrially ob- tained with a thickness of around 10 μm. During immer- sion of the samples, a current density from 2 to 4 A·dm –2 was applied with a temperature of about 25˚C. All elec- trodeposition procedures were obtained in a laboratory of Electronics Enthone Brazil Ltda, which are properties and trademarks of Cookson Electronics Brazil Ltda. Af- ter electrodeposition procedure, a part of the sample was passivated by chemical conversion of blue chromate (PERMAPASS 3080  ). With a potentiostat EG&G PAR 283 support, controlled by programs Softcorr III and Power Suite, interfaced by GPIB plate to a computer for control and data processing, electrochemical tests were * Corresponding author. Copyright © 2012 SciRes. MSA