Effect of aluminium on polarisation parameters and deposit characteristics in typical nickel sulfate electrolyte for electrowinning applications

Abstract

Impurities present in the sulfate electrolyte during nickel electrodeposition influence the electrowinning process and morphology of deposited nickel metal in various ways. The presence of aluminium can be either detrimental or beneficial, depending on its concentration. Effects of the presence of aluminium in the electrolyte during nickel electrowinning were investigated by evaluation of the relationship between nucleation and plating overpotentials, nickel morphology, deposit contamination, internal stress development, and buffer characteristics of the electrolyte. Results showed that aluminium present at concentrations of lower than 1250 mg/L was unfavourable for the electrowinning process and highly strained nickel deposits of poor morphology were produced; at higher concentrations, the presence of aluminium was advantageous for the morphology and internal stress, and correlated with increased buffer characteristics of the electrolyte.