Electrochemical Production of Al-Si Alloys in Cryolitic Melts in a Laboratory Cell

Abstract

Direct production of aluminium-silicon alloy during aluminium electrolysis in fluoride-based melts was studied. Experiments were carried out in a laboratory cell dedicated to current efficiency measurements. Electrolysis was run at 960 °C, 970 °C, and 980 °C at a fixed cathodic current density (CCD) of 0.9 A cm−2 and a cryolite ratio (CR) of 2.2. Silicon content was up to 4 wt.% added via SiO2 precursor. SEM/EDX and ICP-MS were carried out for some of the deposits to characterize the solidified deposit surface of the produced metal and to estimate the current efficiency for Al-Si alloy. It was possible to produce alloys of at least 9.0 wt.% Si in Al with an estimated alloy current efficiency of approximately 63%. The presence of silica in the melt brought a rise in the recorded cell voltage which implies a lowering of the electrolyte conductivity.