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

Abstract

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.

Keywords

sintering atmosphere / corrosion / NiFe₂O₄ ceramic / inert anode / aluminum electrolysis

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