Electrodeposition of Aluminium and Co-Deposition of Alloying Elements Titanium, Manganese and Silicon in Molten Fluoride Electrolyte

Primary aluminium is produced by the Hall-Heroult process which is based on electrolysis in molten fluoride electrolyte, Na3AlF6-AlF3, at ∼960 °C in which the raw material alumina is dissolved and decomposed into pure aluminium and CO2 gas due to the use of carbon anodes. Alloys are made by adding pure metals prior to the casting process. An alternative approach to produce alloys by co-deposition of alloying elements during electrolysis, where metal oxides of alloying elements are added to the electrolyte, is under study. Laboratory experiments were carried out to quantify the impact of co-deposition of alloying elements of titanium, manganese and silicon. Current efficiencies above 90 % and acceptable conversion of metal oxide to metal were obtained for electrodeposition of aluminium alloys with titanium, manganese and silicon. The proposed method for producing aluminium based alloys directly in the Hall-Heroult process may give substantial benefits in terms of cost and efficiency.