The main kinetic features of the aluminum and scandium electrowinning during the electrolysis of the KF-AlF 3 -Al 2 O 3 -Sc 2 O 3 melts were studied by means of voltammetry, stationary polarization, as well as electrolysis. Aluminum electrowinning from the KF-AlF 3 -Al 2 O 3 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 Al 2 O 3 by Sc 2 O 3 in KF-AlF 3 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-AlF 3 -based melts with the addition of Al 2 O 3 and Sc 2 O 3 , electrowinning of aluminum and scandium on a solid cathode, and dissolution of formed cathode deposit in liquid aluminum.

Kinetics of the cathode process in the KF-AlF 3 and KF-AlF 3 -Al 2 O 3 melts has been studied by means of the steady-state polarization and voltammetry techniques. The kinetic parameters of the aluminum electrodeposition in dependence on such factors as cathode material, process temperature, alumina concentration in the melt, etc. were determined. Based on the experiment data analysis, a mechanism of the cathode process in the KF-AlF 3 -Al 2 O 3 melts was proposed. The operating parameters were defined and electrolysis was carried out.

The results of several different tests related to the low-temperature aluminum electrolysis were considered in this work. The role of mass transfer processes in the anode-cathode space was recommended to be significant during electrolysis in the low-temperature KF-AlF3 and NaF-AlF3-based melts. The stationary polarization and voltammetry methods were applied in order to study the kinetics of the electrode processes on the carbon and metal electrodes in the KF-AlF3-Al2O3 melts and to select the electrolysis parameters. The schemes of electrode processes were suggested on the basis of electrochemical tests, the flows of substances in the anode-cathode distance were analyzed and the main reasons of the cathode current efficiency decrease during the low-temperature electrolysis in the KF-AlF3-Al2O3 and KF-NaF-AlF3-Al2O3 melts were discussed. It was revealed that the cathode current density should not exceed 0.4–0.55 A cm−2 during the electrolysis at 750 °C–800 °C.