Various industrial vacuum coating processes require Graphite Suspension and Boron Nitride Suspension as release agents. Both have their advantages as well as disadvantages. This article by Supervac Industries, New Delhi, India is a comparison of the two products.

1. Graphite Suspension vs. Boron Nitride Suspension
Time and again, we are approached by users wanting to know which coating
will be best for their application: graphite suspension or boron nitride
suspension. Often, the same vacuum system manufacturer who earlier
recommended boron nitride suspension is now recommending graphite
suspension or vice versa, as a coating inside the vacuum chamber. This has led
to much confusion amongst the users. In this blog, I have attempted to address
this confusion by stating the properties of both along with the pros and cons of
their use. Either of the two can be selected based on one’s requirement.
Properties of Graphite Suspension:
SV-GS (Supervac Graphite Suspension)
(1)
(2)
(3)
This is made up of very fine graphite particles in either water based
or solvent based suspension. For vacuum coating purposes, water
based suspensions are better suited since they do not release any
vapours and thus do not hinder the vacuum formation process.
Graphite suspension is electrically conductive.
It is thermal resistant in nature.

2. (4)
(5)
(6)
(7)
(8)
(9)
Coated graphite suspension provides an excellent barrier to the
vacuum chamber walls against any chemical or process gases.
Graphite suspension works as an excellent release agent.
It is chemically inert; so does not react to any chemical or molten
metal vapours.
Excellent lubricating properties.
Black in colour.
This is a semi-metal material.
Properties of Boron Nitride Suspension:
SV-BNS (Supervac Boron Nitride Suspension)
(1)
(2)
(3)
(4)
(5)
BN suspension comprises of ultra fine particles of boron nitride in
aqueous base or solvent base. Water based boron nitride suspension
is always better than solvent based for vacuum coating purposes as
the former releases no vacuum hindering vapours.
It is electrically insulating.
It has high thermal conductivity.
It acts as an excellent protective barrier for the vacuum chamber
walls against any chemical or process gases.
BN suspension acts as a release agent, enabling stuck aluminium to
be wiped off the vacuum chamber floor.

3. (6)
(7)
(8)
(9)
It is chemically inert.
Excellent lubricating properties.
White in colour.
This is an Advanced ceramic material.
Even though both these suspensions have a lot in common, there are some
ways that make them uniquely divergent as well.
Comparison:
Graphite suspension
Boron Nitride suspension
1.
2.
3.
4.
5.
6.
Black in colour
Milky white in colour
Slightly messy to use
Non messy
Electrically conductive
Electrically insulating
Thermally resistant
Thermally conductive
Relatively cheap
Expensive
Can withstand temperatures Up to Can withstand temperature Up to
600ºC.
1700ºC.
7. Excellent lubricant
Excellent lubricant
8. Excellent release agent
Excellent release agent
9. Inert
Inert
10. Easy to mix and apply
Easy to mix and apply
Conclusion
Both Graphite suspension and Boron Nitride suspension can be used as a
coating in vacuum chamber to prevent Aluminium from sticking to chamber
walls in Metalizing industry or as a general lubricant in so many other
applications. Both have got the required lubricity and inertness.
Use Boron Nitride Suspension if clean working environment is very important
or an electrically insulating or thermally conductive coating is required. Also
if working temperature is very high.
Use Graphite suspension if cost saving is a major consideration or if coating
has to be electrically conductive or thermally insulating. Also if working
temperature is moderately high (less then 6000C).
Supervac Industries, New Delhi, is number one manufacturer and supplier in
India, of both these products. It supplies both High quality Graphite

4. suspension and Premium quality Boron Nitride suspension to a very large
number of customers all over the world.