Table of Contents
ISRN Materials Science
Volume 2011 (2011), Article ID 356863, 6 pages
http://dx.doi.org/10.5402/2011/356863
Research Article

Electrochemical Behavior of Zn-Ni Alloys in Borate Buffer Solutions

Department of Chemistry, Faculty of Science, South Valley University, Qena 83523, Egypt

Received 23 March 2011; Accepted 18 May 2011

Academic Editors: M. Marcos and H. C. Shih

Copyright © 2011 Ayman M. Zaky 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 Electrochemical behavior of Zn-Ni alloys was studied in borate solutions using cyclic voltammetry, potentiodynamic anodic polarization, and current transient techniques under the effect of alloy composition, stepwise increasing potential, scan rate, and electrolyte concentration. The voltammogram consists of two potential regions separated by the critical potential 𝐸 c r i t . The first potential region involves the selective dissolution of the less noble metal, zinc, and the appearance of two anodic peaks 𝐴 1 and 𝐴 2 . Peak 𝐴 1 is due to the formation of Zn(OH)2 and 𝐴 2 to the formation of ZnO on the alloy surface. The second potential region relates to the simultaneous dissolution of nickel. This region was characterized by the appearance of three anodic peaks 𝐴 3 , 𝐴 4 , and 𝐴 5 prior to the oxygen evolution reaction. These peaks are assigned to the formation of Ni(OH)2, NiOOH, and Ni2O3, respectively. The anodic voltammetric profiles of the alloys lies below those of the pure metals indicating decreased rates of dissolution of the two metals, zinc and nickel, from the alloys. On alloying with nickel, the rate of zinc dissolution was decreased which increases its protective life as sacrificial anode for automobile body against corrosion. X-ray diffraction analysis confirmed the existence of Zn(OH)2, ZnO, Ni(OH)2, and Ni2O3 with preferred orientations (008), (101), (002), and (202) of the alloy surface polarized to noble potentials. Potentiostatic current/time transients showed that the formation of Zn(OH)2, ZnO, Ni(OH)2, NiOOH, and Ni2O3 layers involves a nucleation and growth mechanism under diffusion control.