ELECTRODEPOSITION OF ZN-NI ALLOYS IN SULFATE ELECTROLYTES .2. REACTION MODELING

Citation
Fjf. Miranda et al., ELECTRODEPOSITION OF ZN-NI ALLOYS IN SULFATE ELECTROLYTES .2. REACTION MODELING, Journal of the Electrochemical Society, 144(10), 1997, pp. 3449-3457
Citations number
17
Categorie Soggetti
Electrochemistry
ISSN journal
00134651
Volume
144
Issue
10
Year of publication
1997
Pages
3449 - 3457
Database
ISI
SICI code
0013-4651(1997)144:10<3449:EOZAIS>2.0.ZU;2-B
Abstract
A reaction model has been developed to account for the mechanism of Zn -Ni alloys deposition from acidic sulfate electrolytes. The heterogene ous reactions imply the presence of four adsorbates: (i) ZnNiaddivided by which catalyzes nickel deposition, (ii) the intermediate H-ad invo lved in hydrogen evolution which occurs at low polarizations on nickel -rich deposits, (iii) the intermediate adion Zn-ad(+) acting as a cata lyst for the deposition of the zinc-rich delta-phase which prevails at high polarizations, and (iv) the anionic species Zn/NiSO4,ad2- which inhibits the formation of the delta-phase. In the transition region of intermediate polarizations, an increase in the interfacial pH facilit ates the chemical incorporation of S in deposits, which is catalyzed b y the anionic adsorbate. The model validity has been confirmed by comp arison with experimental polarization curves, electrode impedance meas urements, and analyses of the deposit structures and compositions.