Preliminary testing of NiFe2O4-NiO-Ni cermet as inert anode in Na3AlF6-AlF3 melts
(School of Metallurgical Science and Engineering, Central South University, Changsha 410083, China)
Abstract: The electrical conductivity of cermet 83(90NiFe2O4-10NiO)-17Ni at different temperatures was measured in air, the operating performance of inert anode was evaluated in a laboratory electrolysis cell with various electrolyte compositions. The results indicate that the electrical resistivity of cermet studied has negative temperature coefficient, which is the characteristic of semi-conducting material. The proper addition of AlF3 in the bath can improve the corrosion resistance of cermet inert anode, but excess adding amount will cause the catastrophic corrosion. Post-examination of anodes shows that metal Ni leaches preferentially on the anode surface. Chemical dissolution, electrolyte penetration as well as electrochemical dissolution serve as major corrosion mechanisms.
Key words: aluminium electrolysis; inert anode; NiFe2O4 based cermet; electrical conductivity; corrosion resistance