Chemical and phase compositions of zinc plus nickel alloys determined by stripping techniques

Zinc-nickel alloys were obtained from a bath with a high concentration of ammonium chloride that was previously used to prepare the alloys under industrial conditions. These industrial alloys were characterized with the usual ex situ techniques, while in the present case potentiodynamic and galvanostatic stripping methods were used. Three substrates with different characteristics were selected and in all cases the stripping techniques were shown to be a reliable method for fast determination of both the chemical and phase composition of electrodeposited zinc-nickel alloys. With the plating conditions used in the present work, the oxidation potentials of alpha- and eta-phases coincided with those observed in other cases, while the gamma-phase was oxidized at a significantly more positive potential. This fact could be attributable to a very low value of the exchange current density of zinc from this phase. Moreover, the analysis of the composition of the alloys with different thicknesses revealed that the deposition of the nickel-rich alpha-phase was favoured in the initial stages of the process.