Dissolution Characteristics of Al-Si Alloys in AlCl3-NaCl-KCl Molten Salt at 423 K

Abstract

Herein, the dissolution behaviors of Al-Si casting alloy and cold rolled alloy anodes in AlCl3-NaCl-KCl molten salt were investigated at 423 K to produce high-purity Al from Al-Si alloys. All the Al-Si alloys were purified to more than 99.4 wt% by electrorefining. In particular, the purity of the AC4C and Al-11 %Si alloys was 99.9 wt% each. It was confirmed from linear sweep voltammetry (LSV) measurements that anodic dissolution did not occur in the Si molten salt electrolyte. The dissolution of Al occurred preferentially on the anode surface of the ADC12 alloy during electrolysis, while the undissolved Si formed an enriched layer on the surface. In the ADC12 and AC4C casting alloys, a microstructure identical to that of the bulk metal was observed on the surface after electrolysis. On the contrary, the Si microstructure in the cold-rolled Al-11 %Si alloy was fine, and adhesion was weak and did not remain firmly on the surface. In addition, the Si-enriched layer on its surface did not significantly affect the outcome of the 50-h electrorefining experiment.

Keywords

• electrorefining
• molten salt
• anodic dissolution
• al-si alloy