Milacron Marketing LLC | Cimcool Fluid Technology | Cincinnati, Ohio 45209
CHLORINE AND
METALWORKING
FLUIDS: ISSUES AND
ANSWERS
Chlorine Use In Metalworking Fluids
Where chlorine comes from, what form it can take and
its implications, especially in the aerospace industry:
Chlorine is an element belonging to the same group as
fluorine, bromine and iodine. This group is called the
halogens. Chlorine is the only member of this group currently
of concern.
Chlorine can occur in a metalworking fluid mix in one of
three ways:
1. As a chloroparaffin or chlorinated olefin. This is present as
an extreme pressure (EP) lubricant in some metalworking
fluids which are designed for use on ferrous metals. It is
believed that chlorinated olefins break down chemically under
the influence of (extreme) heat and pressure near the cutting
or grinding zone, to form a solid lubricant film between the
ferrous work piece and the tool. Although the same break
down mechanism and film forming is unlikely in the case of
aluminum, it has been observed that chlorinated olefins can
help in the cutting or grinding of aluminum alloys, especially
automotive alloys. However, since there are other (non-
chlorinated) lubricants that work just as well with aluminum it
is generally best to avoid chlorinated olefins when cutting or
grinding aluminum.
2. As a component (often a contaminant) of one or more of
the ingredients that go to make up the metalworking fluid
concentrate. When we do not want chlorine in the
metalworking fluid concentrate, we obviously avoid any
chlorine containing raw materials.
“Chlorine and Metalworking Fluids: Issues and Answers”
3. As chlorine and chlorides from water. For health reasons,
water is chlorinated and this introduces about 1 to 3 ppm of
chlorine gas into the water. For metalworking purposes, we
can safely ignore this low level of chlorine introduced as a
sterilizing agent. However, water almost always contains
chloride ions (usually as calcium or sodium chloride. These
are natural impurities the water picks up while filtering through
rocks on its way to the reservoir. Typically, city water will
contain about 50 ppm chloride.
Since city water is used to manufacture semi-synthetic and
synthetic metalworking fluids concentrates these products will
contain some chloride ions from this source. However, since
the customer will generally use city water containing at least
50 ppm chloride ions to make the mix the chloride content of
the product becomes insignificant.
(It makes no difference if the customer uses softened water,
chloride ions are not removed by the softening process, only
calcium and magnesium ions are taken out. All ions,
however, are removed if the customer is using deionized or
RO (reverse osmosis) water.
How much chlorine ?
A product containing a chlorinated EP lubricant will contain
comparatively large amounts of chlorine, in the form of
organic chloro- compounds. A typical figure (for a 5% mix)
would be 0.25% chlorine (2500 ppm chlorine).
If the product contains a chlorine containing raw material
(other than a chlorinated EP lubricant) then this might
contribute 0.001% to 0.01% chlorine (10 to 100 ppm chlorine)
to a 5% mix. A comparatively low level. If the chlorine is
present as the chloride ion, simply as part of the water used in
the manufacture of the metalworking fluid concentrate and as
the water used to make the mix, then typical figures for
chlorine content would be 0.002% to 0.005% (20 - 50 ppm
chlorine).
If the customer is using deionized or RO water to make the
mix then a concentrate that contained 50 ppm chlorine, would
yield a mix containing only about 2 or 3 ppm chlorine
(assuming a 5% mix was made). Thus, only if the product
contains a chlorinated EP additive (chlorinated olefin), or
other organic chloro-compound is the level of chlorine in
Milacron Marketing LLC Technical Report No. J/N 96/35
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