Electrolytic Production of Aluminum Alloys in Cells with a Low-Consumption Metal Anode and a Wettable Cathode

Abstract The possibility of producing aluminum alloys during low-temperature electrolysis in cells with vertical low-consumption metal anodes and wetted cathodes is shown. Aluminum alloys are fabricated by electrolysis of KF–NaF (10 wt %)–AlF3–Al2O3 melt with a certain cryolite ratio (CR) in a galvanostatic mode in cells with a vertically arranged Fe–Ni–Cu metal anode and a borated graphite cathode at 830°C. The electrolysis proceeds at a constant voltage of 2.8 ± 0.1 V for 14 h. The source of alloying components for aluminum alloys is the Fe–Ni–Cu metal anode, on the surface of which an oxide layer forms during electrolysis. The concentration of alloying metals in the resulting aluminum remains almost constant or increases slightly during electrolysis. To study the interaction of the oxide layer with the electrolyte components using isothermal saturation, we used the isothermal saturation method to determine the solubility of the Fe2O3 and NiO oxides in low-melting potassium cryolite-based melts KF–AlF3 and KF–NaF (10 wt %)–AlF3 with a cryolite ratio CR = 1.3–1.5 in the temperature range 750–850°C. The solubility of Fe2O3 in the cryolite melts decreases with increasing NaF concentration and decreasing CR. In the KF–NaF (10 wt %)–AlF3 electrolyte with CR = 1.3, the solubility of Fe2O3 is lowest (0.016 wt % at 820°C) among all the melts under study. At temperatures exceeding the corresponding liquidus temperatures by 30–90°C, the solubility of NiO in the low-melting cryolite melts is an order of magnitude lower than that of Fe2O3.