Effect of sintering atmosphere on corrosion resistance of Ni/(NiFe2O4-10NiO) cermet inert anode for aluminum electrolysis

A comparative study on the corrosion resistance of 17Ni/(NiFe2O4-10NiO) cermet inert anode prepared in different sintering atmospheres was conducted in Na3AlF6-Al2O3 melt. The results indicate that the corrosion rates of NiFe2O4-based cermet anodes prepared in the vacuum and the atmosphere with oxygen content of 2×10−3 (volume fraction) are 6.46 and 2.71 cm/a, respectively. Though there is a transition layer with lots of holes or pores, a densified layer is formed on the surface of anode due to some reactions producing aluminates. For the anode prepared in the atmosphere with oxygen content of 2×10−3, the thickness of the densification layer (about 50 μm) is thicker than that (about 30 μm) formed on the surface of anode prepared in the vacuum. The contents of NiO and Fe(II) in NiFe2xO4-y-z increase with the decrease of oxygen content in sintering atmosphere, which reduces the corrosion resistance of the material.