Effect of sintering atmosphere on corrosion resistance of NiFe2O4 ceramic in Na3AlF6-Al2O3 melt

摘要

A comparative study on the corrosion resistance of NiFe2O4 ceramic inert anode for aluminum electrolysis prepared in the different sintering atmosphere was carried out in Na3AlF6-Al2O3 melt. The results show that the corrosion rates of NiFe2O4 ceramic inert anodes prepared in the vacuum and the atmosphere with oxygen content of 1×10-2 are 6.08 cm/a and 2.59 cm/a, respectively. A densification layer is formed at the surface of anode due to some reactions which produce aluminates. For the anode prepared in the atmosphere with oxygen content of 1×10-2, the thickness of the densification layer (about 50 μm) is thicker than that (about 20 μm) formed at the surface of anode prepared in the vacuum. The content of NiO and Fe(II) in Ni(II)xFe(II)1-xFe(III)2O4 increases with the decrease of the oxygen content of sintering atmosphere, which reduces the corrosion resistance of the material.