Antifreeze is an additive which can be used to lower the freezing point – and also raise the boiling point – of any liquid that is water-based. One common example is from the automotive industry where antifreeze, in the form of ethylene glycol, is added to water as the engine coolant in vehicles and prevents the engine freezing in cold temperatures.
If little or no antifreeze was used and water froze in the engine, it would create massive internal pressure through expansion, resulting in severe engine damage. Likewise, an overheated engine can have damaging (and expensive) consequences. Coolant caring for your car is key!
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What is Antifreeze Made Of?
Antifreeze can be made using any of these four main agents mixed with water: methanol, glycerol, ethylene glycol and propylene glycol. Each agent has advantages and disadvantages, depending on how you want to use it.
- Methanol: a highly combustible, toxic liquid, methanol is used in vehicle windscreen washer fluid and de-icers.
- Glycerol (also called glycerine): non-toxic and able to withstand higher temperatures than its counterparts, glycerol was the first antifreeze used in car engines. Sometimes called ‘nature’s antifreeze’, it can be made from animal and vegetable matter.
- Ethylene glycol: the most common car antifreeze, used over glycerol due to its lower freezing point even though it’s toxic to humans. Ethylene glycol also the best antifreeze for providing protection against both cold and hot temperatures due to its heat transfer characteristics.
- Propylene glycol: less toxic than ethylene glycol but has to be used in larger quantities to achieve the same result. Ideal for use where ethylene glycol would be dangerous, such as in the food industry.
These formulations can be sold as concentrate or as a dilution with water. A 50%:50% dilution, which gives a freezing point of approximately -37°C (-34.6°F), is typically used in the UK but in warmer or colder climates, weaker or stronger dilutions are used as necessary.
Antifreeze may also contain other additives such as phosphates and silicates which help protect against corrosion and growth of biological matter. The benefit of this is that if corrosion or biological matter were allowed to build up, they could limit the effect of the antifreeze and cause damage.
Why Does Antifreeze Come in Different Colours?
You may know that antifreeze comes in a variety of colours, from red and blue to green and orange, created by adding dye. Why? Mainly for historical reasons – the different colours reflected either where the product was made, the brand that made it, or the type of corrosion-preventing chemical it contained.
For example, older antifreezes used inorganic additive technology and were either blue or green. As technology progressed, antifreezes became silicate-free and used organic acid technology. These extended-life antifreezes tended to be orange. These days, the colour doesn’t reflect the product itself so it’s not easy to know which chemicals the antifreeze contains just by seeing whether it’s blue, green, yellow or orange.
Is Antifreeze the Same as Coolant?
When referring to the liquid in an engine’s cooling system, antifreeze and coolant are words that can be used interchangeably because they both describe the liquid that helps the engine run at the right temperature.
The difference between antifreeze and coolant is that an engine needs to be cooled to the right temperature 365 days a year no matter the weather, meaning that an engine needs a coolant at all times. When it’s cold, the coolant’s antifreeze properties should prevent the liquid from freezing.
The History of Antifreeze
Charles Adolphe Wurtz, a French chemist, discovered ethylene glycol in the late 1850s, but couldn’t find any uses for it. Around fifty years later, ethylene glycol was found to be an excellent coolant, and was also used as a replacement for glycerol in explosions during the First World War. After the war, it was manufactured on a large scale for engine coolants and was revolutionary in the expansion of both the automotive and aviation industries. Antifreeze as we know it now has a wide number of uses.
Antifreeze Specifications
Antifreeze Blue – Ready to Use
| Description | Limits | Units |
| Appearance | Clear blue liquid, free from particles | |
| Density @ 20°C | 1.055 – 1.075 | g/ml |
| Monoethylene Glycol content | 47 – 50 | % w/w |
| Conforms to BS 6580 2010 | ||
| Freezing Point (as supplied) | <-35 | °C |
Non-Toxic Antifreeze
| Description | Limits | Units |
| Appearance | Clear, colourless liquid | |
| Meets ASTM D3306 Type II, ASTM D 4985, SAE J 1034, BS 6580 (1992), AFNOR NF R15-601 | ||
| S.G. @ 15°C (ASTM D 4052) | 1.030 – 1.065 | g/ml |
| Equilibrium reflux boiling point°C (ASTM D 1120) | >152 | °C |
| pH (50% vol) | 7.5 – 9.5 | |
| Freezing Point 50% vol dilution with water | -34 | °C |
| Freezing Point 33% vol dilution with water | -15 | °C |
Antifreeze Material Safety Data Sheet (MSDS)
Antifreeze material safety data sheets list the compounds considered significant safety hazards when used according to recommendations, including sodium silicate, sodium borate, and denatonium benzoate.
Antifreeze MSDSs list the potential hazards (including health, fire, reactivity and environmental hazards) of antifreeze and how to use or work with it safely.
And Finally…Producing Antifreeze to Stay Warm
Incredibly, in 2014 scientists announced that they had discovered five families of Antarctic dwelling fish which naturally produce ‘antifreeze’ proteins, enabling them to survive in the frigid Southern Ocean. This ability makes them so successful that these fish comprise over 90% of the total fish biomass in the area.
