PRODUCT INFORMATION
INDEX
DATE
Dep. 2
IO-C-M-20-001e D
February 2016
COOLING WATER QUALITY AND TREATMENT
4/6
Natural water alkalinity generally derives from the presence of three types of ions: bicarbonates, carbonates and
hydroxides.
Some waters will contain other compounds (borates, silicates, phosphates, etc.) which contribute to their
alkalinity; but, in practice, the effect of these compounds is insignificant and can be disregarded.
Total dissolved solids:
Solid substances appear in most waters as suspended materials or colloidal solutions.
They are measured in laboratory by the filtration method. Fine solids generate turbidity (NTU and JTU).
Turbidity is measured by the effect of light on these particles.
Conductivity.
Electrical conductivity is the capacity of inorganic salts in solution (electrolytes) to conduct
electricity. Pure water hardly conducts electricity which is however conducted by water containing dissolved
salts. Positively and negatively charged ions are the elements that conduct electricity; the amount of
conduction depends on the number of existing ions and their mobility.
Iron (Fe). Iron dissolved in groundwater to its iron form II. This form is soluble and usually causes no problem
by itself but iron II is oxidized to form iron III which are hydroxides and are insoluble in water. These are
corrosive red dyeing compounds and cause blockage of screens, pumps, pipes and recirculation systems etc.
The use of distilled or de-ionised water increases the risk of corrosion and it is therefore necessary to add
corrosion inhibitors. Such additives can be rust-preventive products used alone or diluted in the antifreeze.
Additives. Antifreeze
The best way of avoiding problems due to corrosion, oxidation, scale, deposits, etc. in the cooling system is to
treat water with adequate additives which will protect the metallic surfaces of the system. These products form a
rust-proofing film on the surfaces of the cooling system, preventing corrosion and inhibiting settlements.
Thus, engine corrosion and rust can be minimised using different types of anticorrosion additives.
Additive
Protection / Purpose
Disadvantage
Phosphates
(PO4)
Steel, iron, aluminium
Unstable, fast wearing, deposits (caused by hard water).
Borates (BO4)
Iron
Corrode aluminium at high temperature.
Tolytriazol (TT)
Copper
Nitrites NO2
Iron (cavitation) and steel
Fast wearing. They expand welds. Dangerous if combined
with amines.
Silicates SiO3
Aluminium, Iron, general,
relative neutralisation
Fast wearing. Form films and, if excessive, they produce a
"green paste" that impairs heat transfer.
Carboxylic acids
Aluminium, general, stable,
neutralisers
Antifreeze products are glycol-based water-soluble liquids (e.g. ethylene glycol, propylene glycol), which generally
contain the above mentioned additives whose object is to prevent the effects of corrosion, deposits, foam, etc.
Therefore, in order to prevent cooling water from freezing, it is recommended to add good quality commercial
antifreeze, even in hot climate areas, because such product raises the boiling point of cooling water, which
impedes that water boils and evaporates.
An inadequate concentration will not only reduce frost protection or the boiling risk, but also increase cooling water
corrosiveness.
The antifreeze-coolant ratio depends on the ambient temperature at the place of installation of the engine and it is
the antifreeze supplier who should state the concentration based on its product specifications and take
responsibility for any secondary effects.
4.1.8
O&M_2.002211.810_A_10_2016
