Passivation of zinc in concentrated alkaline solution—I. Characteristics of active dissolution prior to passivation

✍ Scribed by L.M. Baugh; A. Higginson

• Publisher: Elsevier Science
• Year: 1985
• Tongue: English
• Weight: 604 KB
• Volume: 30
• Category: Article
• ISSN: 0013-4686
• DOI: 10.1016/0013-4686(95)80008-5

✦ Synopsis

As a preliminary stage in the study of the active~passive transition on zinc in concentrated (6.8 mol dm-3) solutions of KOH the reported mechanisms have been reviewed and the characteristics of active dissolution prior to passivation have been investigated. The theory of Armstrong and Bulman has been extended in order to relate all the experimentally important parameters. These include electrode potential, current, angular electrode rotation speed and surface concentrations of Zn(OH) 2-and OH-ions. In common with other observations, it is demonstrated that zinc dissolves quasi-reversibly over a considerable range of potentials. The relationship of this behaviour to other metal/metal-ion systems is discussed. At high current densities ( > 100 mAcm-2) depletion of hydroxide ions occurs at the zinc surface causing a severe deviation in the exponential dependence of the active dissolution current on potential.