Graphite has a low friction coefficient and
very high thermal stability (2000°C [3632°F] and above).
However, practical application is limited to a range of 500
to 600°C (932 to 1112°F) due to oxidation. Furthermore,
because graphite relies on adsorbed moisture or vapors to
achieve low friction, use may be further limited. At
temperatures as low as 100°C (212°F), the amount of water
vapor adsorbed may be significantly reduced to the point
that low friction cannot be maintained. In some instances
sufficient vapors may be extracted from contaminants in the
surrounding environment or may be deliberately introduced to
maintain low friction. When necessary, additives composed of
inorganic compounds may be added to enable use at
temperatures to 550°C ( 1022°F). Another concern is that
graphite promotes electrolysis. Graphite has a very noble
potential of + 0.25V, which can lead to severe galvanic
corrosion of copper alloys and stainless steels in saline
waters.
