Datasheet

Kanthal Appliance Alloys Handbook. 21
5
Corrosion Resistance
Corrosive or potentially corrosive consti-
tuents can considerably shorten wire life.
Perspiring hands, mounting or supporting
materials or contamination can cause corro-
sion.
Steam
Steam shortens the wire life. This effect is
more pronounced on NIKROTHAL alloys
than on KANTHAL alloys.
Halogens
Halogens (fluorine, chlorine, bromine and
iodine) severely attack all high-temperature
alloys at fairly low temperatures.
Sulphur
In sulphurous atmospheres KANTHAL
alloys have considerably better durability
than nickel-base alloys. KANTHAL is
particularly stable in oxidising gases contain-
ing sulphur, while reducing gases with a
sulphur content diminish its service life.
NIKROTHAL alloys are sensitive to
sulphur.
Salts and oxides
The salts of alkaline metals, boron com-
pounds, etc. in high concentrations and are
harmful to heating alloys.
Metals
Some molten metals, such as zinc, brass,
aluminium and copper, react with the resist-
ance alloys. The elements should therefore
be protected from splashes of molten metals.
Ceramic support material
Special attention must be paid to the ceramic
supports that come in direct contact with the
heating wire. Firebricks for wire support
should have an alumina content of at least
45 %. In high-temperature applications, the
use of sillimanite and high-alumina firebricks
is often recommended. The free silica (un-
combined quartz) content should be held low.
Iron oxide lowers the melting point of the
ceramics. Water glass as a binder in cements
must be avoided.
Embedding compounds
Most embedding compounds including
ceramic fibres are suitable for KANTHAL
and NIKROTHAL if composed of alumina,
alumina-silicate, magnesia or zirconia.