OPEN WIRE HEATING ELEMENT – CONDITIONING PROCEDURE
“The durability of “Iron-chrome” resistance alloys at high temperatures is greatly increased by an oxide surface layer formed by a reaction with the oxygen in air.
The protective nature of this oxide layer is proportional to its area and depth. Any foreign matter usually interferes with the formation of the oxide layer, and this causes a reduced element life.
At high temperatures the protective layer of Iron-chrome materials consists almost entirely of aluminum oxide.
It has a light grey color and good chemical resistance.
At temperatures below 1000°C (1832°F) the oxide layer has a dark color since the aluminum oxide is not quite as pure.
In order to protect elements from the effects of harsh environments, it is very desirable to condition the elements, by pre-oxidizing them.
This is accomplished by firing them to a temperature of 1050°C/1922°F and soaking for several hours, 7-10 if possible.
The process is also enhanced by allowing a good air flow into the kiln – leave the peepholes open, or the Kiln vent on.
If you are doing reduction firings in an electric kiln it is desirable to periodically re-oxidize the elements, for best life expectancy.
The results of element conditioning can be quite dramatic.
It may not have much affect for normal, low temperature firings, but can be significant for harsh operating conditions.