THE STABILITY OF REFRACTORY MATERIALS
FOR USE IN MAGNESIUM ELECTROLYSIS CELLS
A. S. Chesnokov,
D. E. Denisov,
and B. Zh. Zhenisov
Translated from Novye Ogneupory, No. 5, May, 2005, pp. 22 – 24.
Results for a range of refractory materials for use in industrial magnesium electrolysis cells are reported. The
Alkorit-98 and Alkor-94S corundum-based castables have shown superior performance characteristics; of
these, a higher thermal stability was found in the low-cement Alkorit-98 owing to its more compact fine-po
The stability of refractory materials used in fabrication of
the lining of electrolysis magnesium cells is a property of ut-
most importance. A route towards improving the electrolytic
production of magnesium is to extend the service life of the
electrolysis cell which is primarily controlled by thermal and
chemical durability of the lining exposed to molten alkali
and alkaline-earth metal chlorides. The accelerated failure of
the lining is also promoted by multiple thermal cycling and
chemical attack of molten magnesium.
The conventional refractory materials (such as chamotte
(fire clay) and mullite, or refractory castables which as a
mixture of calcium aluminate cement (15(25%) and a refrac-
tory filler (high-alumina or standard chamotte, corundum,
bauxite) (fail to meet the ever-demanding requirements
placed on the electrolytic production of magnesium. The slag
zone of a magnesium electrolysis cell made up of chamotte
or mullite refractory materials suffers a complete failure and
wears down within 12 – 16 months of service. Further use of
the failed electrolysis cell will require a thorough hot repair
of the lining by hard manual labor under heavy conditions of
intense heat and gas release. Incipient failure involves
wear-out of the masonry mortar between refractory compo
nents and development of microcrack and cracks under mul
tiple thermal cycle conditions. Electrolytic magnesium im
pregnated in the refractory enters into a chemical reaction
with the material of the lining:
2Mg(l) + SiO
(s) ® (2MgO(s) + Si(l).
This reaction is accompanied by a change in volume
(amounting to 57%), which results in the occurrence of ther-
mal stresses and crack growth .
Fusion-cast mica crystalline materials, in particular,
, have gained acceptance
as the lining material for magnesium electrolysis cell .
Fluorophlogopite exhibits a low porosity, high chemical and
thermal stability, and enhanced mechanical strength in com-
parison with chamotte or mullite refractories or standard
heat-resistance castables. Replacing chamotte or mullite
refractories by fluorophlogopite makes it possible to extend
the service life of electrolysis cell from 22 – 24 to 30 months.
A high-alumina, high-cement refractory castable has
been recommended for the lining of magnesium electrolysis
cells  Chemical composition of the castable was, wt.%:
, 74 – 78; CaO, 10 – 14, and SiO
, ³ 0.5. Density of the
specimens sintered at 800°C was 2.7 – 2.8 g/cm
, and com
pressive strength was 40.0 MPa. Long-term tests of this
castable exposed to the attack by molten magnesium and
magnesium chloride has shown that its stability was some
what higher than the stability of chamotte or mullite
refractories and lower than that of fluorophlogopite. Finally,
it was decided that the castable in question should be with
drawn from use.
In recent years, low-cement castables (1 – 10%) have
found use in the lining of magnesium electrolysis cells.
These castables are multicomponent mixtures composed of
ultra-disperse powders, dispersants, and additives to control
the setting and hardening rates. Low-cement castables dis
play high density, low porosity, small pore size, and en
hanced mechanical strength and thermal stability. To our
knowledge, no data on the stability of low-cement castables
Refractories and Industrial Ceramics Vol. 46, No. 4, 2005
1083-4877/05/4604-0233 © 2005 Springer Science+Business Media, Inc.
All-Russia Aluminum-Magnesium Institute (VAMI), St. Peters
burg; Aliter-Axi JSC, St. Petersburg; Ust’-Kamenogorsk Tita
nium-Magnezium Kombinat, Ust-Kamenogorsk, Russia.