Anodic behaviour of the Cu82Al8Ni5Fe5 alloy in low-temperature aluminium electrolysis

A Cu82Al8Ni5Fe5 wt.% alloy was evaluated as an inert anode in the electrolysis of an Al2O3-saturated, KF35.6–NaF12–LiF3–(AlF3)49.4 melt (790 °С) for 73 h. It was shown that metal consumption at the alloy/scale interface led to the formation of a ring-like gap that was filled with oxygen-free electrolyte. It was hypothesised that the electrochemical transfer of the alloy components through the gap occurred and the chemical oxidation of the alloy particles after the dissolution-deposition process took place in the scale. It was concluded that the rate of scale formation was governed by the percentage of current that had passed through the gap.

► A Cu82Al8Ni5Fe5 wt.% alloy performed as a dimensionally stable anode for 73 h.
► A gap filled with oxygen-free electrolyte was formed at the alloy/scale interface.
► Electrochemical transfer of alloy components through the gap occurred.
► It is concluded that Al in the alloy did not protect the alloy from oxidation.
► 2% of current consumed by the secondary electrochemical process after 73 h.