Based on research on cermet inert anodes for aluminium production, it has been suggested
that nickel ferrite spinel might be suitable for use as a sidewall refractory in Hall-Héroult
cells. A corrosion resistant sidewall would allow elimination of the frozen bath ledge, and has
potentially huge benefits in terms of energy savings and increased productivity. However,
little work has been done to assess nickel ferrite’s suitability as a refractory.
Dense nickel ferrite samples were prepared and characterized, and corrosion tests in cryolite
based baths were conducted. Results confirm that the spinel does have good corrosion
resistance. The corrosion mechanism is complex, involving grain boundary attack and
formation of a Ni – Fe alloy. This alloy could pose a risk in terms of contamination of the
aluminium. The use of additives to restrict penetration of grain boundaries may be the key to
development of a successful spinel based refractory.