Antifreeze, or coolant, is a certified name for coolant designed to protect the engine from freezing and overheating. The composition of antifreeze is a mixture of distilled water, non-freezing base and a package of modifying additives.
The main purpose of coolant is to stabilize the operating temperature of the engine during fuel combustion in the cylinder block. Operation of the motor without coolant can lead to instant engine failure (jamming pistons, cracks in the unit housing, etc.).
The service life of the mechanisms and their effective operation largely depends on the quality of the emulsion used.
Initially, water was used to cool the engines. Its main drawback is the high freezing threshold (0°C). At the time of freezing, the liquid greatly increased in volume and tore the cooling jacket.
To lower the crystallization point, monatomic alcohols (ethyl, methyl, etc.) were tried to be added to the water, but they had a low boiling point (60-80°C) and increased evaporation.
In addition, the water is rich in salts and minerals that precipitate or form insoluble deposits on the inner surfaces of the cooling system when the temperature rises.
In 1920 there was the first ice-free composites. They were made on the basis of triatomic alcohol – glycerin, which froze at a temperature of -40°C and boiled at +290°C. the Main disadvantages of such products were – high viscosity and increased evaporation.
Only in 1930 ethylene glycol compounds were used as a basis for the production of low-freezing liquids. Ethylene glycol is a poisonous chemical that freezes at -12°C.
In its pure form, the reagent is characterized by high aggressiveness towards metal and polymer surfaces. For safe use as an antifreeze, distilled water and a number of modifying additives are added to the solution.
The main technical requirements for coolant are resistance to temperature decrease. To comply with such conditions of modern commercially available emulsions of the following types:
- coolant–To – concentrated composition for the manufacture of antifreeze with their hands.
- coolant–65 – mixtures in which the crystallization threshold is in the range ≤ 65°C.
- coolant–40 – solutions with freezing point -40°C.
All these classes of low-freezing liquids are produced in the factory by diluting alcohol compounds with distilled water.
Types of antifreezes
Depending on the basic components, coolants are divided into several categories:
On the basis of inorganic substances – salts of silicates, nitrates, phosphates, borates, etc. the Main drawbacks are the ability to form insoluble alkaline deposits on the inner surfaces of the motor.
Is a transparent liquid of blue color. In the CIS, they are United under the common name – «Tosol». In the modern version – a silicate substance. They are most compatible with aluminum alloys (radiator, engine).
Produced on the basis of salts of carboxylic acids (carboxylates). Coolant red or purple, with high anti-corrosion properties. Unlike previous coolers, they do not create a continuous protective film, but act selectively – only on corrosion foci.
Characterized by low viscosity and high mobility, which often leads to the depressurization of compounds.
Aqueous solution of organic (carboxylic) and inorganic (silicate, phosphate) salts of orange or green color. Service life – up to 5 years.
Made by bipolar technology, consist of a mixture of organic corrosion additives and silicon compounds. Boiling point – ≤ 130°C. service Life – 5 years or more. The compositions are painted in red or purple.
Low-freezing liquids of orange or yellow color are the last word in the production of cooling solutions. They are characterized by high antioxidant and anti-corrosion properties. Suitable for cooling systems of all types of internal combustion engines.
Alcohol-containing coolant differ in the percentage of water and the composition of the package of modifying additives that determine the temperature threshold of crystallization of mixtures.
According to GOST 28084-89 standards, low-freezing solutions should be characterized by the following parameters:
1). Density at +20°C. The higher the density, the higher the temperature of the liquid. This condition is applicable to emulsions in which the content of distilled water is equal to 35-50%. Violation of the proportion of mixtures can lead to both an increase and a decrease in the temperature of crystallization of antifreeze.
2). The freezing point at which ice crystals begin to form in the solution. The lower and upper limits of crystallization can be adjusted by the percentage of ethylene glycol and water in the solution. It should be noted that the compositions of different manufacturers may differ from each other due to differences in the set of modifiers.
3). Alkalinity. This parameter determines the volume content of corrosion inhibitors in antifreeze and indicates their effectiveness in eliminating oxidative processes. The normal value for coolant is in the range of 10-15 units.
4). Foaming. This value shows the amount of foam (in cm3) that can form in the system after 5 minutes of engine operation, as well as the stability of its formations in seconds.
5). Hydrogen index (pH), measured at 200°C. Characterized by the magnitude of the aggressiveness of the coolant components to the metal surfaces of the motor. Exceeding the permissible limits (7,5–11) leads to the destruction of aluminum parts.
6). Corrosion activity of antifreeze. The value shows how many g/m2 of the surface has been corroded over a period of time.
7). Boiling point (°C). The higher the critical level, the lower the risk of coolant boiling, steam jams and engine failure.
Classification of antifreezes
Until a certain time, the generally accepted specification of antifreezes such as engine oil did not exist. Regulatory requirements from different manufacturers depended on the models and design features of the engine. In Russia is GOST 28084-89, USA – ASTM D, BS – great Britain, etc.
Volkswagen and BASF were the most active in this direction. They achieved average results (1970), which were recognized by all automobile concerns. Manufacturers of modern liquids to some extent adhere to the parameters developed by these enterprises.
Volkswagen legalized the following classification:
- G11 is produced on the basis of diatomic alcohol compositions with the addition of inorganic modifiers. By its color (blue, green) and performance is a complete analogue of the Soviet cooling liquids «Antifreeze» and «Lena».
- G12 – ethylene glycol, water and a package of carboxylate additives. Emulsions are marked in bright red. Mixing with G11 is strictly prohibited.
- G12+ is a purple liquid with an advanced set of organic additives. Recommended for Volkswagen, Audi, Skoda cars since 2001
- G13 – high-tech modern antifreezes with improved environmental properties. Solutions of orange or yellow color made on the basis of propylene glycols. Recommended for use in Volkswagen cars of 2010 and later.
The compatibility of different chemical composition of liquids is determined according to the specifications of the manufacturer. If there are no instructions to compensate for the amount of antifreeze better than distilled water.