Effect of NiO content on corrosion behaviour of Ni-xNiO-NiFe2O4 cermets in Na3AlF6-Al2O3 melts
(School of Metallurgical Science and Engineering, Central South University,
Changsha 410083, China)
Changsha 410083, China)
Abstract: 5Ni-xNiO-NiFe2O4 cermets with different NiO contents were prepared and the corrosion behaviour in Na3AlF6-Al2O3 melts was investigated in laboratory electrolysis tests. The results indicate that adding NiO is un-favorable to the densification of NiFe2O4-xNiO ceramics, while small Ni doping can greatly improve the sintering property. The electrolysis tests show that excess NiO is beneficial to the reduction of Fe while has little effects on that of Ni in the bath; the steady-state concentrations of Ni, Fe are below the corresponding solubilities of NiFe2O4-xNiO, implying that corrosion mechanism changes while electrifying. Post-electrolysis examination of anodes shows that Ni metal leaches at the anode surface, yet the substrate ceramic prevents the penetration of bath and the further loss of metal phase.
Key words: NiFe2O4; cermet; corrosion behavior; inert anode; aluminum electrolysis