Removing the ledge formation in the Hall-Heroult cell during the electrolysis process may
significantly reduce the energy requirement of the aluminium production process. In the absence of
the ledge, however, the sidewall-material types become heavily restricted since the cryolite is very
corrosive at the electrolysis temperatures. This paper study the corrosion behaviour of sintered nickel
ferrite, nickel aluminate, and magnesium aluminate refractories (as possible candidates for sidewall
material) in molten aluminium and cryolite melts with various alumina content at 980°C. Immersion
tests of refractories with various porosity were conducted to assess the suitability of the refractories
in the corrosive environment of the electrolysis cells. Microstructural change of the refractory after
immersion were analysed using secondary scanning electron microscopy (SEM). Sampling of the
melts were taken at 0, 10 min, 30 min, and each hour up to 6 hrs, and subsequently analysed by
Inductively Coupled Plasma (ICP) spectroscopy. Based on the projected concentration of the
refractories constituents in the melts, it was predicted that the corrosion rate of NiFe2O4, NiAl2O4 and
MgAl2O4 in cryolite with 11 wt per cent Al2O3 were 461 × 103, 1.03 × 103, and 798 × 103 cm/a,
respectively. Much lower corrosion rate of 2.3 cm/a for NiFe2O4, 2.6 cm/a for NiAl2O4 and 0.3 cm/a
for MgAl2O4 were predicted if the refractories in contact with aluminium melts. Erosion played an
important role in the corrosion as the concentration of the refractory constituents in the melts were
beyond its solubility limit. It is therefore crucial to increase the densities of the refractory and improve
its wetting characteristics.