O. Sych; T. Kot
The main types of cooling liquids for motor vehicles are considered. Various liquids are used to cool internal combustion engines. In the warm season, when the air temperature is above 00 С, the best cooling liquid is water. At temperatures below 00 С, liquids with a low freezing point – antifreeze are used. Low-freezing coolants – antifreezes are prepared by mixing water with one or more components that have the ability to lower the freezing point of the solution. The best lowfreezing coolants are mixtures of water with glycols – ethylene glycol and propylene glycol. To improve performance, an additive package is added to the antifreeze compound. Depending on the nature of the additives, modern antifreezes are divided into three types: traditional, carboxylate and hybrid.
Traditional antifreezes (“tosol cooling liquid” and modifications) contain inorganic additives and have small (no more than 2 years) service life, while they do not withstand high (more than 1080 C) temperatures. According to the proposed classification of the Volkswagen Audi Group, traditional antifreezes with inorganic additives are designated G11.
Hybrid antifreezes (G11+) contain organic and inorganic inhibitors (usually silicates or phosphates). Service life is up to 3 years.
Carboxylate antifreeze (G12) contains corrosion inhibitors based on higher carboxylic acids salts (carboxylates). Carboxylate antifreezes have the longest operating life; it is up to 5 years.
Establishing the nature of additives is an urgent task in the study of cooling fluids for motor vehicles.
It has been proposed to use the method of molecular spectroscopy in the infrared region of the spectrum for the identification of carboxylate additives in antifreeze. For the study, evaporated antifreeze samples 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 above absorption bands are not typical for traditional (G11) and hybrid (G11+) antifreezes and can be used to identify carboxylate additives in the composition of cooling liquids. This makes it possible to differentiate antifreezes by species.
During performance testing of various types of antifreezes, it has been found that carboxylate antifreezes are inert to products (automotive radiators) made of aluminium and aluminium alloys, whereas traditional and hybrid antifreezes have corrosive effects on aluminium and its alloys. The results of operational tests of various types of antifreeze will be considered in the next publication.