TM 5-3895-359-14&P
Non-Chromates
Non-chromate inhibitors (berates, nitrates, nitrites, etc.)
provide corrosion protection in the cooling system with
the basic advantage that they can be used with either
water or a water-and-antifreeze solution.
INHIBITOR SYSTEMS
An inhibitor system is a combination of chemical
compounds which provide corrosion protection, pH
control and water-softening ability. Corrosion protection
is discussed under the heading Corrosion Inhibitors
Vital. The pH control is used to maintain an acid-free
solution. The water-softening ability deters formation of
mineral deposits. Inhibitor systems are available in
various forms such as coolant filter elements, liquid and
dry bulk inhibitor additives and as an integral part of
antifreeze.
Coolant Filter Elements
Replaceable elements are available with various
chemical inhibitor systems. Compatibility of the element
with other ingredients of the coolant solution cannot
always be taken for granted.
Problems have developed from the use of the
magnesium lower support plate used by some
manufacturers in their coolant filters. The magnesium
plate will be attacked by solutions which will not be
detrimental to other metals in the cooling system. The
dissolved magnesium will be deposited in the hottest
zones of the engine where heat transfer is most critical.
The use of an aluminum or zinc support plate in
preference to magnesium is recommended to eliminate
the potential of this type of deposit.
High chloride coolants will have a detrimental effect on
the water-softening capabilities of systems using ion-
exchange resins.
Accumulations of calcium and
magnesium ions removed from the coolant and held
captive by the zeolite resin can be released into the
coolant by a regenerative process caused by high
Fig. 2 Coolant Freezing and Boiling Temperatures
chloride-content solutions.
vs. Antifreeze Concentration (Sea Level)
use in Detroit Diesel engines. These systems can be
Bulk Inhibitor Additives
used with either water or water-and-antifreeze solutions
Commercially packaged inhibitor systems are available
and provide corrosion protection, pH control and water
which can be added directly to the engine coolant or to
softening. Some non-chromate inhibitor systems offer
bulk storage tanks containing coolant solution.
the additional advantage of a simple on-site test to
determine protection level. Since they are added
Both chromate and non-chromate systems are available
directly to the coolant, require no additional hardware or
and care should be taken regarding inhibitor
plumbing.
compatibility with other coolant constituents.
All inhibitors become depleted through normal operation
Non-chromate inhibitor systems are recommended for
and additional inhibitor must be added to
10-9-15
