ZnNi alloy electrodeposition from acid baths containing sorbitol or glycerol and characterization of ZnNi deposits

Abstract

The influence of sorbitol or glycerol on the electrodeposition of ZnNi alloys and on the morphology, composition and structure of the ZnNi deposits was investigated. The highest current efficiency (CE), around 90%, was obtained in the presence of glycerol in the potential range from approximately −1.30 V to −1.40 V, while in the presence of sorbitol or absence of either polyalcohol the CE was 82–85%, for the same potential range. Scanning electron microscopy (SEM) analysis showed that ZnNi deposition at −1.26 V or −1.40 V from a bath with sorbitol led to the formation of more compact deposits than with glycerol. Energy dispersive X-ray spectroscopy (EDS) analysis showed that the Ni content in the deposit obtained in the presence of sorbitol remained in the range of 7–9.5 wt% Ni, over a large range of deposition conditions. On the other hand, ZnNi deposits with variable Ni content (5.5–19.5 wt% Ni) were obtained from baths with glycerol or without either polyalcohol, by shifting the deposition potential. All ZnNi deposits showed uniform distribution of the elements Zn and Ni. X-ray analysis of ZnNi deposits obtained from plating baths with and without polyalcohol’s at −1.26 and −1.40 V presented the γ, γ1 and Pt3–Zn phases.