O. Sych; T. Kot
All major types of cooling liquids for motor vehicles are describes herein. Various liquids are used to cool internal-combustion engines. Water is the best cooling liquid in the warm season, when the air temperature is above 00С. Liquids with a low freezing point, namely antifreeze agents are used at temperatures below 00С. Low-freezing coolants – antifreeze agents are prepared by mixing water with one or more components that have the ability to lower the freezing point of the solution. The best low-freezing coolants are mixtures of water with glycols – ethylene glycol and propylene glycol. An additive package is added to the antifreeze compound to improve performance. Depending on the nature of the additives, modern antifreeze agents are divided into three types: traditional, carboxylate and hybrid.
Traditional antifreeze agents (”tosol cooling agent” and modifications) contain inorganic additives and have a small (no more than 2 years) service life, while they do not stand high (more than 1080C) temperatures. According to the classification of the Volkswagen Audi Group proposed by the group of companies, traditional antifreezes with inorganic additives are designated with symbol G11.
Hybrid antifreeze agents (G11+) contain organic and inorganic inhibitors (usually silicates or phosphates). Their service life is up to 3 years.
Carboxylate antifreeze agents (G12) contains corrosion inhibitors based on salts of higher carboxylic acids (carboxylates). Carboxylate antifreezes obtain the longest operating life of up to 5 years.
When conducting operational tests of various types of antifreeze agents for compliance with the requirements of National State Standard 28084-89 (СТ СЭВ 2130-80), “Low-freezing cooling liquids. General technical specifications” it was found that carboxylate antifreezes are inert to products (automobile radiators) made of aluminum and aluminum alloys, while traditional and hybrid antifreezes have a corrosive effect on aluminum and its alloys.
An urgent task in the study of cooling fluids for motor vehicles is the establishment of the nature of additives.
For the identification of carboxylate additives in antifreeze agents, it has been proposed to use the method of molecular spectroscopy in the infrared region of the spectrum. For the study, evaporated samples of antifreeze agents are used. Carboxylate additives are characterized by the presence of absorption bands caused by vibrations of carboxyl groups (COOH) at 1560 cm-1 to 1580 cm-1. The abovementioned absorption bands are not typical for traditional (G11) and hybrid (G11+) antifreeze agents and can be used to identify carboxylate additives in the composition of cooling liquids. This makes it possible to differentiate antifreeze agents by species.
Key words: automobile antifreeze, operational properties, identification, spectral method.