MATERIALS TRANSACTIONS
Online ISSN : 1347-5320
Print ISSN : 1345-9678
ISSN-L : 1345-9678
Electrodeposition Behavior of a Zn–Ni Alloy in an Alkaline Zincate Solution
Hiroaki NakanoShingo ArakawaYuya TakadaSatoshi OueShigeo Kobayashi
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2012 Volume 53 Issue 11 Pages 1946-1951

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Abstract

Electrodeposition behavior of Zn–Ni alloys was investigated at current densities of 10–500 A·m−2 and a charge of 5 × 104 C·m−2 in an unagitated zincate solution containing triethanolamine, which forms a stable complex with Ni2+ ions at 308 K. At low current densities, the Zn–Ni alloy exhibited normal codeposition, wherein electrochemically more noble Ni deposited preferentially, while at high current densities, it exhibited anomalous codeposition, wherein less noble Zn deposited preferentially. Ni deposition and H2 evolution were significantly suppressed in the region of anomalous codeposition at higher current densities, showing the formation of an inhibitor for deposition, which results from Zn2+ ions in the cathode layer. In contrast, in the region of normal codeposition at lower current densities, the underpotential deposition of Zn apparently occurred with Ni. Because Zn–Ni alloys are composed of a stable intermetallic compound of Ni5Zn21, the activity coefficient of Zn in the deposit appears to decrease remarkably.

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© 2012 The Japan Institute of Metals and Materials
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