Electrowinning of Aluminum and Scandium from KF-AlF3-Sc2O3 Melts for the Synthesis of Al-Sc Master Alloys

Abstract

The main kinetic features of the aluminum and scandium electrowinning during the electrolysis of the KF-AlF3-Al2O3-Sc2O3 melts were studied by means of voltammetry, stationary polarization, as well as electrolysis. Aluminum electrowinning from the KF-AlF3-Al2O3 melt on tungsten cathode occurs in the potential range from −0.1 to −1.3 V relative to the potential of the aluminum electrode. Replacing Al2O3 by Sc2O3 in KF-AlF3 melts leads to a co-electrowinning of aluminum and scandium with the same kinetic parameters. Based on the electrochemical measurements, the parameters of stable galvanostatic electrolysis of the melts under study were selected and electrolysis tests were carried out to obtain Al-Sc master alloys. The cathode current efficiencies during co-electrowinning of aluminum and scandium on tungsten were evaluated, and the microstructure of the obtained Al-Sc master alloys was studied. A novel approach for the synthesis of the Al-Sc master alloys proposed that includes the electrolysis of the KF-AlF3-based melts with the addition of Al2O3 and Sc2O3, electrowinning of aluminum and scandium on a solid cathode, and dissolution of formed cathode deposit in liquid aluminum.