Study on the impact of potassium and sodium ions on the ammonia method for zinc refining

The effects of potassium and sodium ions on the zinc leaching rates within the ZnCl₂-NH₃-NH₄Cl-H₂O zinc refining process system were studied, the influence patterns of K⁺ and Na⁺ on the cathode throughout the electrodeposition process examined, and the impacts of K⁺ and Na⁺on the quality of zinc coatings, current efficiency, power consumption, as well as the composition, structure, and morphology of these coatings throughout the electrodeposition process further explored. The findings demonstrate that the zinc leaching rate incrementally decreases as the concentration of K⁺ and Na⁺in the solution increases in the leaching process. Throughout the electrodeposition process, with an increase in the concentration of K⁺ and Na⁺in the electrolyte, the nucleation overpotential (NOP) value diminishes, the corrosion current density escalates, and the corrosion rate accelerates, culminating in diminished current efficiency, heightened power consumption, and a lowered zinc coating yield, which adversely affects the deposition of cathodic zinc. The increased concentrations of K⁺ and Na⁺in the electrolyte will not only induce alterations in the morphology of the zinc coatings but may produce salt crystallization, which can accelerate electrode wear and corrosion.