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at links here related changes upload file permanent link page information cite this page get shortened url switch to legacy parser print export download as pdf printable version in other projects wikimedia commons wikidata item appearance move to sidebar hide from wikipedia the free encyclopedia liquid additive an antifreeze is an additive which lowers the freezing point of a water based liquid an antifreeze mixture is used to achieve freezing point depression for cold environments common antifreezes also increase the boiling point of the liquid allowing higher coolant temperature 1 however all common antifreeze additives also have lower heat capacities than water and do reduce water s ability to act as a coolant when added to it 2 because water has good properties as a coolant water plus antifreeze is used in internal combustion engines and other heat transfer applications such as hvac chillers and solar water heaters the purpose of antifreeze is to prevent a rigid enclosure from bursting due to expansion when water freezes commercially both the additive pure concentrate and the mixture diluted solution are called antifreeze depending on the context careful selection of an antifreeze can enable a wide temperature range in which the mixture remains in the liquid phase which is critical to efficient heat transfer and the proper functioning of heat exchangers most if not all commercial antifreeze formulations intended for use in heat transfer applications include anti corrosion and anti cavitation agents that protect the hydraulic circuit from progressive wear principles and history edit water was the original coolant for internal combustion engines it is cheap nontoxic and has a high heat capacity it however has only a 100 kelvin liquid range and it expands upon freezing to address these problems alternative coolants with improved properties were developed freezing and boiling points are colligative properties of a solution which depend on the concentration of dissolved substances salts for example lower the melting points of aqueous solutions and as such are commonly used for de icing due to their low cost however salt solutions typically cannot be used in cooling systems because they induce corrosion of metals solutions of organic compounds especially alcohols in water are effective alcohols such as methanol ethanol ethylene glycol etc have been the basis of all antifreezes since they were commercialized in the 1920s 1 use and occurrence edit automotive and internal combustion engine use edit fluorescent green dyed antifreeze is visible in the radiator header tank when car radiator cap is removed most automotive engines are water cooled to remove waste heat though the water used is actually a mixture of water and antifreeze the term engine coolant is widely used in the automotive industry which covers its primary function of convective heat transfer for internal combustion engines when used in an automotive context corrosion inhibitors are added to help protect vehicles radiators which often contain a range of electrochemically incompatible metals aluminum cast iron copper brass solder etc water pump seal lubricant is also added antifreeze was developed to overcome the shortcomings of water as a heat transfer fluid on the other hand if the engine coolant gets too hot it might boil while inside the engine causing voids pockets of steam leading to localized hot spots and the catastrophic failure of the engine if plain water were to be used as an engine coolant in northern climates freezing would occur causing significant internal engine damage also plain water would increase the prevalence of galvanic corrosion proper engine coolant and a pressurized coolant system obviate these shortcomings of water with proper antifreeze a wide temperature range can be tolerated by the engine coolant such as 34 f 37 c to 265 f 129 c for 50 by volume propylene glycol diluted with distilled water and a 15 psi pressurized coolant system early engine coolant antifreeze was methanol methyl alcohol ethylene glycol was developed because its higher boiling point was more compatible with heating systems engine coolant standards edit the volkswagen group has been particularly committed to the development of coolants and their standards vw tl 774 in collaboration with haertol chemie from magdeburg vw standards include g11 g12 g12 g12 g13 and g12evo another company involved in the development is basf glysantin whose standards are g30 g40 g48 g05 g33 and g34 volkswagen group g11 vw tl 774 c g12 g12 vw tl 774 d f g12 vw tl 774 g g13 vw tl 774 j g12evo vw tl 774 l basf glysantin g48 matches vw tl 774 c glysantin g30 matches vw tl 774 d f glysantin g40 matches vw tl 774 g and vw tl 774 j glysantin g64 matches vw tl 774 l 3 4 other industrial uses edit the most common water based antifreeze solutions used in electronics cooling are mixtures of water and either ethylene glycol egw or propylene glycol pgw the use of ethylene glycol has a longer history especially in the automotive industry however egw solutions formulated for the automotive industry often have silicate based rust inhibitors that can coat and or clog heat exchanger surfaces ethylene glycol is listed as a toxic chemical requiring care in handling and disposal ethylene glycol has desirable thermal properties including a high boiling point low freezing point stability over a wide range of temperatures and high specific heat and thermal conductivity it also has a low viscosity and therefore reduced pumping requirements although egw has more desirable physical properties than pgw the latter coolant is used in applications where toxicity might be a concern pgw is generally recognized as safe for use in food or food processing applications and can also be used in enclosed spaces similar mixtures are commonly used in hvac and industrial heating or cooling systems as a high capacity heat transfer medium many formulations have corrosion inhibitors and it is expected that these chemicals will be replenished manually or under automatic control to keep expensive piping and equipment from corroding biological antifreezes edit antifreeze proteins refer to chemical compounds produced by certain animals plants and other organisms that prevent the formation of ice in this way these compounds allow their host organism to operate at temperatures well below the freezing point of water antifreeze proteins bind to small ice crystals to inhibit growth and recrystallization of ice that would otherwise be fatal 5 6 cryoprotectants are commonly used in cryobiology to prevent or inhibit freezing in sperm blood stem cells plant seeds etc 7 8 ethylene glycol propylene glycol and glycerol all used in automotive antifreeze are commonly used as biological cryoprotectants 7 8 primary agents edit ethylene glycol edit main article ethylene glycol ethylene glycol most antifreeze is made by mixing distilled water with additives and a base product usually meg mono ethylene glycol or mpg mono propylene glycol ethylene glycol solutions first became available in 1926 and were marketed as permanent antifreeze since the higher boiling points provided advantages for summertime use as well as during cold weather they are used today for a variety of applications including automobiles but there are lower toxicity alternatives made with propylene glycol available when ethylene glycol is used in a system it may become oxidized to five organic acids formic oxalic glycolic glyoxalic and acetic acid inhibited ethylene glycol antifreeze mixes are available with additives that buffer the ph and preserve alkalinity of the solution to prevent oxidation of ethylene glycol and formation of these acids nitrites silicates borates and azoles may also be used to prevent corrosive attack on metal ethylene glycol has a bitter sweet taste and causes inebriation the toxic effects of ingesting ethylene glycol occur because it is converted by the liver into 4 other chemicals that are much more toxic the lethal dose of pure ethylene glycol is 1 4 ml kg 3 us fluid ounces 90 ml is lethal to a 140 pound 64 kg person but is much less lethal if treated within an hour 9 see ethylene glycol poisoning propylene glycol edit propylene glycol propylene glycol is considerably less toxic than ethylene glycol and may be labeled as non toxic antifreeze it is used as antifreeze where ethylene glycol would be inappropriate such as in food processing systems or in water pipes in homes where incidental ingestion may be possible for example the u s fda allows propylene glycol to be added to a large number of ultra processed foods including ice cream frozen custard salad dressings and baked goods and it is commonly used as the main ingredient in the e liquid used in electronic cigarettes propylene glycol oxidizes to lactic acid 10 besides cooling system corrosion biological fouling also occurs once bacterial slime starts to grow the corrosion rate of the system increases maintenance of systems using glycol solution includes regular monitoring of freeze protection ph specific gravity inhibitor level color and biological contamination propylene glycol should be replaced when it turns a reddish color when an aqueous solution of propylene glycol in a cooling or heating system develops a reddish or black color this indicates that iron in the system is corroding significantly in the absence of inhibitors propylene glycol can react with oxygen and metal ions generating various compounds including organic acids e g formic oxalic acetic these acids accelerate the corrosion of metals in the system 11 12 13 14 other antifreezes edit propylene glycol methyl ether is used as an antifreeze in diesel engines it is more volatile than glycol 1 once used for automotive antifreeze glycerol has the advantage of being non toxic withstands relatively high temperatures and is noncorrosive it is not however used widely 1 glycerol was historically used as an antifreeze for automotive applications before being replaced by ethylene glycol 15 16 volkswagen introduced g13 tl 774 g antifreezes containing glycerol in 2008 marketed as better for the environment due to its low toxicity and reduced co 2 emissions 17 however since 2018 they have moved on to g12evo tl 774 l which no longer contains glycerol 18 glycerol is mandated for use as an antifreeze in many sprinkler systems citation needed measuring the freeze point edit once antifreeze has been mixed with water and put into use it periodically needs to be maintained if engine coolant leaks boils or if the cooling system needs to be drained and refilled the antifreeze s freeze protection will need to be considered in other cases a vehicle may need to be operated in a colder environment requiring more antifreeze and less water three methods are commonly employed to determine the freeze point of the solution by measuring the concentration 19 specific gravity using a hydrometer test strip or some sort of floating indicator refractometer which measures the refractive index of the antifreeze solution and test strips specialized disposable indicators made for this purpose both specific gravity and refractive index are affected by temperature although the former is affected much less catastrophically temperature compensation is nevertheless recommended for ri measurement 19 propylene glycol solutions cannot be tested using specific gravity because of ambiguous results 40 and 100 solutions have the same specific gravity 19 although typical uses rarely exceed 60 concentration the boiling point can be similarly determined by a concentration given from one of the three methods datasheets for glycol water coolant mixtures are commonly available from chemical vendors 20 corrosion inhibitors edit most commercial antifreeze formulations include corrosion inhibiting compounds and a colored dye commonly a fluorescent green red orange yellow or blue to aid in identification 21 a 1 1 dilution with water is usually used resulting in a freezing point of about 34 f 37 c depending on the formulation in warmer or colder areas weaker or stronger dilutions are used respectively but a water antifreeze ratio of 40 60 to 60 40 is frequently specified to ensure corrosion protection and 70 30 for maximum freeze prevention down to 84 f 64 c 22 23 maintenance edit in the absence of leaks antifreeze chemicals such as ethylene glycol or propylene glycol may retain their basic properties indefinitely by contrast corrosion inhibitors are gradually used up and must be replenished from time to time larger systems such as hvac systems are often monitored by specialist firms which take responsibility for adding corrosion inhibitors and regulating coolant composition for simplicity most automotive manufacturers recommend periodic complete replacement of engine coolant to simultaneously renew corrosion inhibitors and remove accumulated contaminants traditional inhibitors edit traditionally there were two major corrosion inhibitors used in vehicles silicates and phosphates american made vehicles traditionally used both silicates and phosphates 24 european makes contain silicates and other inhibitors but no phosphates 24 japanese makes traditionally use phosphates and other inhibitors but no silicates 24 25 organic acid technology edit most modern cars are built with organic acid technology oat antifreeze e g dex cool 26 or with a hybrid organic acid technology hoat formulation e g zerex g 05 27 both of which are claimed to have an extended service life of five years or 240 000 km 150 000 mi dex cool specifically has caused controversy litigation has linked it with intake manifold gasket failures in general motors gm s 3 1l and 3 4l engines and with other failures in 3 8l and 4 3l engines one of the anti corrosion components presented as sodium or potassium 2 ethylhexanoate and ethylhexanoic acid is incompatible with nylon 6 6 and silicone rubber and is a known plasticizer class action lawsuits were registered in several states of the us and in canada 28 to address some of these claims the first of these to reach a decision was in missouri where a settlement was announced early in december 2007 29 late in march 2008 gm agreed to compensate complainants in the remaining 49 states 30 gm motors liquidation company filed for bankruptcy in 2009 which tied up the outstanding claims until a court determines who gets paid 31 according to the dex cool manufacturer mixing a green non oat coolant with dex cool reduces the batch s change interval to 2 years or 50 000 km 30 000 mi but will otherwise cause no damage to the engine 32 dex cool antifreeze uses two inhibitors sebacate and 2 eha 2 ethylhexanoic acid the latter which works well with the hard water found in the united states but is a plasticizer that can cause gaskets to leak 24 according to internal gm documents 32 the ultimate culprit appears to be operating vehicles for long periods of time with low coolant levels the low coolant is caused by...