Effect of NiO addition on the high-temperature oxidation and corrosion behaviors of Fe–Ni alloy as inert anode material for aluminum electrolysis

Abstract

A new type of Fe–Ni ceramet inert anode with the NiO contents of 0, 10, 20 and 30 wt% for aluminum electrolysis was prepared by the powder metallurgy process. The effects of NiO addition on the high-temperature oxidation and corrosion behaviors of the ceramet had been investigated by the thermogravimetric analysis and electrolysis, respectively. The results indicated that the pre-existing oxide phase shortened the time for formation of the oxide scale on the sample, which promoted the formation of continuous dense scale with the good adhesion to substrate materials during high-temperature oxidation. Besides, the appearance of NiO at the grain boundary hindered the oxidation of the metal phase, which avoids the peeling phenomenon. As a result, the addition of NiO in the Fe–Ni alloy played an important role in hindering the oxidation process, which greatly improved the anti-oxidant properties. Compared with the alloy anode, additionally, the total impurity content in the melted aluminum electrolyte was 0.28 mass% for 100 h of electrolysis at 20 A. It indicated that the addition of NiO improved the corrosion resistance of Fe–Ni ceramet anode significantly. Therefore, the Fe–Ni ceramet anode may be the promising inert anode materials for the aluminum electrolysis.