Lubezine Magazine Vol. 9 April - June 2014 | Page 15

See also

Nigerian lubes
market standards P.28

Controlling Oxidation
Different ways or methods
can be used to eliminate or
control the rate of oxidation in
lubricants.

Temperature
Heat is often accelerates the
oxidation process because
temperature has two effects
on any reaction. The first effect
involves activation energy. If the
system contains enough energy
to push the reaction over the
threshold, the reaction will
continue while if the energy is
not enough, nothing will happen.
The second effect is related
to the speed of the reaction.
The rate of Oxidation will
approximately double for every
10°C increase in temperature
above 60oC as indicated as
the Arrhenius rate rule. This
will mean that the lubricant
life will be reduced by 50% or
one-half for every 10°C increase
in temperature. Hence one of
the vital ways to reduce the rate
of oxidation is controlling of the
lubricant temperature.

Use of Antioxidants

for numerous lubricant problems which
include:
• Increase of viscosity of the lubricant
• Introduction of varnish on the equipment
• Formation of sludge in the system
• Formation of sediments
• Depletion of additives in the lubricant
• Breakdown of the base oil
• Plugging of the oil filters
• Increasing of the total acid number(TAN)
• Increase of foaming in the lubricant in
service.
• Increase in rust formation and corrosion.
Therefore, understanding and controlling oxidation is a priority of the lubricant
chemist.

.

February-April 2014 | LUBEZINE MAGAZINE

Antioxidants or oxidation
inhibitors are used to break into
the growth and regeneration
of the free radicals that are
stable, thus halting the cycle.
The different types of oxidation
inhibitors used in lubricants can
be classified as UV Absorbers,
Peroxide degenerators and
electron donors or acceptors
that break the chain.

Using a good base oil
Slowing the lubricant aging
process or oxidation is largely
dependent upon the quality
of the lubricant raw materials
selected, beginning with the
base oil which is the largest
lubricant raw material. Use of
Hydro-treated base oils in some

cases will also reduce the rate
of oxidation as it has very low
contaminant when produced.

Use of Synthetic
lubricants
Some synthetics, such as
polyalphaolefins (PAO), have
inherently better oxidation
stability than mineral oils. This
improved oxidation stability
enables the lubricant to operate
at slightly higher operating
temperature than the mineral
lubricant.

Use of detergents
Detergents are used to
clean up the by product of
oxidized oil which occurs when
antioxidants can’t neutralize the
acids effectively by creating a
chemical reaction with sludge,
and varnish precursors so to
neutralize them and keep them
soluble.

Detection and Filtration
of wear metals
Early detection of wear metals
is very important to be able to
reduce the propagation of the
oxidation process free radicals.
This detection can be done
using the used oil analysis.
After detection the wear metals
should be filtered in most cases
for large volume systems use
of external filtration system can
be adopted. In other systems,
the filtration system should be
in good condition to be able to
trap the wear metals.

Dealing with
contaminants
Any contaminant that contain
oxygen or introduces oxygen
should be dealt with at earliest
opportunity. This includes air
and water. This will drastically
reduce the rate of oxidation of
any lubricant.

.

13