A substance added to water in the cooling system of an engine to prevent the system freezing during cold weather. This is necessary since water expands when it freezes, and this can lead to cracking in those parts of the engine where the cooling system is circulated. Substances used as anti-freeze include ethanol and methanol, which can evaporate from water solution; ethylene-glycol does not evaporate, but is more expensive.
Antifreeze is a water-based liquid coolant used in gasoline and diesel engines. The term 'colligative agent' is to be preferred as, in warm climates, the benefit of these compounds is to increase the boiling point of the coolant, which should then be more properly referred to as 'anti-boil', and as anti-freeze decreases and increases both properties, respectively, 'colligative agent' more accurately describes the liquid.
Until the late 1930s, methanol was the most widely used antifreeze.
Ethylene glycol solutions became available in 1937 and were marketed as "permanent antifreeze", since the higher boiling points provided advantages for summertime use as well as during cold weather. Ethylene glycol antifreezes are poisonous and should be kept away from any person or animal (children and especially dogs) that might be tempted by its sweet taste.
Should ingestion of antifreeze occur, ethanol (alcoholic beverages) can be administered until proper treatment can be started in order to slow the conversion of methanol to formaldehyde and formic acid which are the substances responsible for methanol's toxicity.
For this reason bittering agent (denatonium benzoate) is usually added to engine coolant to make it taste unpleasant.
Propylene glycol, on the other hand, is considerably less toxic and may be labelled as "non-toxic antifreeze". It is used as antifreeze where ethylene glycol would be inappropriate, such as in food-processing systems or in pipes in homes, as well as numerous other settings. However, it should not be thought that propylene glycol based antifreeze is safe for consumption.
In the 1980's inventor Jack Evans discovered the advantages of using a waterless coolant. His final formulation is a mixture of ethylene glycol and propylene glycol.
Most commercial antifreeze formulations include corrosion inhibiting compounds, and a colored dye (commonly a green, red or blue fluorescent) to aid in identification.
Glycol antifreeze solutions should generally be replaced with fresh mixture every two years. Many modern cars now come filled with organic acid technology (OAT) antifreeze (such as Dex-Cool), which has an extended service life of five years. Although these still contain glycol, OAT solutions may not be compatible with conventional inorganic-based coolants containing glycol (e.g., with silicates, borates, phosphates) and, if changing from one type to the other, the cooling system must be thoroughly flushed with clean water. Typically OAT antifreeze contains a red or pink dye to differentiate it from the conventional inorganic coolants (blue or green). Some of the newer technology OAT coolants claim to be compatible with all types of OAT and inorganic-based coolants;
If ingested, the antidote for antifreeze is usually ethanol or fomepizole.
User Comments Add a comment…