The importance of cathode zinc morphology as an indicator of industrial electrowinning performance

A number of recent papers have described the use of cyclic voltammetry measurements as a method of controlling the electrowinning step in zinc production. A further advance has been the use of XRD to characterize the crystal orientation of zinc deposits. This paper concerns the use of these techniques by the Electrolytic Zinc Company of Australasia Limited to specify zinc electrowinning conditions during a pilot plant evaluation of a novel zinc plant circuit. Preliminary small scale electrolysis tests gave unsatisfactory deposits and low current efficiencies ( < 85%). The aforementioned techniques were used diagnostically to make step changes to oper­ating conditions and to cell additives. The approach was successful and current efficiencies of 93 % were established. The use ofXRD, coupled with extensive experience of zinc electrowinning, proved to be more important than cyclic voltammetry. The preferred conditions generated by the small scale tests were successfully implemented in pilot plant trials using a full sized electrolytic cell producing 0.5 t per day of zinc. Overall, the tests confirmed the expectation that there is a strong correlation between current efficiency and the morphology of zinc deposits.