The influence of sorbitol on zinc film deposition, zinc dissolution process and morphology of deposits obtained from alkaline bath

Authors: Pereira, M.; Barbosa, L.; Souza, C.; Moraes, A.; Carlos, I.

Source: Journal of Applied Electrochemistry, Volume 36, Number 6, June 2006 , pp. 727-732(6)

Publisher: Springer

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Abstract:

A novel cyanide-free zinc deposition bath was developed in which sorbitol was added at various concentrations. Voltammetric studies indicated that the reduction process is influenced thermodynamically and kinetically by the sorbitol concentration. Also, two cathodic processes were observed, one (wave) associated with the hydrogen evolution reaction (HER) on 1010 steel, the other (peak) with zinc bulk reduction, simultaneous to the HER. Furthermore, the plating-process kinetics was controlled by mass transport. The presence of sorbitol in the bath led to formation of light-grey zinc films, even during the HER, without cracks and dendrites. Plating current efficiency decreased from ∼ ∼62% to 43% on increasing the sorbitol concentration in the plating bath. In the presence of 0.1 M <EquationSource Format="TEX"><![CDATA[$$[hbox{Zn(OH)}_{4}]^{2-}$$]]></EquationSource> and/or sorbitol concentrations higher than 0.2 <Emphasis Type="SmallCaps">M</Emphasis>, Zn electrode dissolution was inhibited. However, a small dissolution of zinc electrode was observed with 0.05 <Emphasis Type="SmallCaps">M</Emphasis> sorbitol in alkaline solution without zincate. SEM micrographs showed that the 1010 steel substrate was fully covered by Zn film and that the sorbitol affected the morphology of zinc films, acting as a grain refiner.

Keywords: alkaline bath; scanning electron microscopy; sorbitol; zinc deposition and dissolution

Document Type: Research article

DOI: http://dx.doi.org/10.1007/s10800-006-9133-z

Affiliations: 1: Email: diac@power.ufscar.br

Publication date: 2006-06-01