Properties of Antifreeze Solution

solution than when using water. However, 100 percent

concentrated antifreeze compound has a boiling point far

above safe operating temperatures for water-cooled

engines and should not be used for coolant except with

water added.

Alcohol antifreeze solutions boll at

temperatures below the boiling point of water.

(3) Evaporation. Loss of freezing protection from

evaporation is no problem In antifreeze solutions.

Practically all coolant losses are leakage and overflow

losses of liquid, and the only way that freezing protection

of the solution can be lost is through adding water.

(4) Foaming of coolant. Some natural waters have a

greater tendency to foam than others, due to minerals or

impurities contained in them. Contamination of antifreeze

solution or aging of solution from extended service

increases foaming tendencies. Foaming condition of

coolant does not mean a head of foam on the surface of

the coolant in the radiator, but refers to small air bubbles

which are caught and held in the body of the coolant,

giving coolant a milky appearance and increasing its

volume.

(5) Coolant leakage. The leakage rate of inhibited

antifreeze solutions is no more than that of water, although

it may appear to be more. The explanation for the

appearance of more wetness at small leaks with the

antifreeze solution is that antifreeze compound evaporates

more slowly than water. Leakage difficulties with either

water coolant or antifreeze solution can be avoided only by

proper attention to preventive maintenance leakage

services (figs 2-2, 2-8, and 2-9).

(6) Chemical Properties.

While water itself is

Figure 2-27. Relation between concentration of antifreeze

chemically very stable, it attacks certain cooling system

compound in solution and freezing protection of solution.

metals quite vigorously under the influence of heat and

aeration, conditions constantly present during cooling

b. Properties of Antifreeze Solution. Some of the

system operation (para 2-16). To protect the system from

differences between antifreeze solution and water have a

corrosion, it is necessary to use corrosion inhibitor in water

bearing on cooling system preventive maintenance.

coolant Inhibitors already contained In antifreeze

(1) Freezing point. Adding 60 percent antifreeze to

compound have two purposes.

40 percent water lowers the freezing point of water in

(a) They prevent the corrosive attack of water used

proportion to amount added until the lowest possible

in preparing solution.

freezing protection, -62F, is reached. Solutions which

(b) They prevent deterioration of the antifreeze

contain more than 60 percent antifreeze compound give

compound, so that the solution remains noncorrosive for

less protection.

at least one winter's use under average operating

conditions.

NOTE

c. Evaporation. Any evaporation from antifreeze

When preparing antifreeze solutions, current

solutions is practically all water. Losses of solution from

directives should be consulted.

the cooling system by evaporation are negligible as

compared to other causes of coolant loss (para 2-28f).

(2) Boiling Point The addition of antifreeze

d. Heat Transfer Antifreeze solutions have slightly

compound to water raises the boiling point of the coolant.

less ability to carry away heat than water However,

A solution containing one-third antifreeze compound,

protecting to 0 F, has a boiling point of 220 F as

compared to 212 F for water, and a 60 percent solution

boils at 231 F. Cooling systems can therefore operate at

higher temperatures without boiling when using antifreeze

2-25