ISSN 0104-6632 Printed in Brazil www.abeq.org.br/bjche Vol. 28, No. 03, pp. 475 - 482, July - September, 2011 *To whom correspondence should be addressed Brazilian Journal of Chemical Engineering EFFECT OF NICKEL AND MAGNESIUM ON ZINC ELECTROWINNING USING SULFATE SOLUTIONS V. F. C. Lins 1* , M. M. R. Castro 2 , C. R. Araújo 3 and D. B. Oliveira 4 1 Chemical Engineer, D. Sc., Corrosion and Surface Engineering Laboratory, Federal University of Minas Gerais, Phone: + (55) (31) 34091780, Fax: + (55) (31) 34091726, Av. Antônio Carlos 6627, Zip Code 31270-901, Belo Horizonte - MG, Brazil. * E-mail: vanessa.lins@pq.cnpq.br 2 Chemical Engineer, D. Sc., Corrosion and Surface Engineering Laboratory, Federal University of Minas Gerais, Zip Code 31270-901, Belo Horizonte - MG, Brazil. E-mail: deia@deq.ufmg.br 3 M.Sc. Metallurgical Engineering, Metallurgical Engineer, Catholic University of Minas Gerais, E-mail: carlosroberto_araujo@yahoo.com.br 4 Chemical Engineer, M.Sc., Corrosion and Surface Engineering Laboratory, Federal University of Minas Gerais, Phone: + (55) (31) 3409-1780, Fax: + (55) (31) 34091726, Av. Antônio Carlos, 6.627, Zip Code 31270-901, Belo Horizonte - MG, Brazil. E-mail: doug.bruno@yahoo.com.br (Submitted: February 20, 2011 ; Revised: March 25, 2011; Accepted: March 30, 2011) Abstract - Zinc electrowinning is performed with the application of a current through insoluble electrodes (Pb-Ag), causing the electrolysis of zinc sulfate, with or without impurities, and zinc deposition on the cathode of aluminum. The impurities can reduce the current efficiency and increase the energy consumption in zinc electrolysis. In this work, the effect of nickel and magnesium on zinc electrodeposition was studied using the electrochemical techniques of galvanostatic deposition and cyclic voltammetry. Additions of nickel, magnesium or both cations in zinc sulfate electrolyte resulted in a marginal increase in current efficiency. Addition of nickel or magnesium polarizes the cathode; however, the extent of polarization in the presence of magnesium is more than that of nickel. Addition of magnesium to the zinc electrolyte caused zinc reduction at a more negative potential. The addition of nickel to the zinc electrolyte increased the current density of the anodic peaks, thus increasing the dissolution of zinc and hydrogenated phases. The addition of nickel to the zinc and magnesium solutions decreased the nucleation loop, facilitating zinc deposition. Keywords: Electrolysis; Electrolytic zinc; Nickel; Magnesium; Cyclic voltammetry. INTRODUCTION One of the greatest changes in the last forty years concerning the application of steel as a structural element was the use of zinc-coated steels for situations that demand a higher corrosion resistance. Galvanized steel can be applied in all industrial segments that normally use cold rolled steels, such as the automotive industry, auto parts, metallic vehicle bodies, home appliances, electro-electronic equipment, steel furniture, civil construction and containers. Zinc is consumed as zinc oxide by several industries such as rubber vulcanizing, cosmetics, medical, and polymers (Roberge, 1999). One method of production of electrolytic zinc is electrowinning by using sulfate solutions. A current is applied through insoluble electrodes, which causes zinc deposition on the cathode. Several parameters