Antifreeze and special fluids

Antifreeze is often seen only as a frost protection agent, although corrosion behavior is far more important, because the cooling system has ideal conditions for the development of corrosion. If corrosion inhibitors are not sufficiently represented or not mutually consistent , damage to the refrigerant system and the engine itself can occur. The chemical composition is decisive for the quality of the refrigerant. The basic structure of the refrigerant is:

BASE FLUID + ADITIVES + WATER

Base fluid - monoethylene glycol (MEG), or less commonly propylene glycol.

AdDitives - corrosion, cavitation and deposition inhibitor, antifoam, stabilizer and buffer.

Water - it must be distilled or demineralized, and the pH value at 20°C = 7 - 8, in new types, due to the absence of silicate and phosphate, hard water can be used.

The undiluted refrigerant (concentrate) should contain at least 90% MEG, at most 4% water, and the other components are additives. The coolant must meet a number of requirements such as: low freezing point, high boiling point, low coefficient of volumetric expansion, minimum viscosity, non-flammability, not to foam and not cause changes in structural materials, good heat conductivity, high specific heat, etc.

Today on the market there are three basic types of antifreeze, which differ in their chemical composition and mechanism of action:

• IAT – Traditional antifreeze. Replacement period 1 to 2 years.
• HOAT – Long Life Hybrid Antifreeze - Organic Corrosion Inhibitors with Silicates (SOAT) / or Nitrites (NOAT). Replacement period 3 years.
• OAT – Long Life Organic antifreeze. Replacement period 5 years.

Traditional antifreeze (IAT) is based on monoethylene glycol and inhibitors to protect motor vehicle cooling systems from freezing and corrosion. It does not contain amines, phosphates and nitrites. The corrosion inhibitor package contains silicates. Meets international standards: BS 6580, AFNOR NF R15-601, SAE J1034, ONORM V 5123: 2009, ASTM D3306-08a. The replacement period of this type of antifreeze is two years.

Hybrid antifreeze (HOAT) is based on monoethylene glycol of G11 quality. It contains a hybrid package of inhibitors based on silicates and salts of organic acids. It does not contain nitrites, amines or phosphates. Meets the following quality standards: ASTM D 3306, ASTM D 4985, SAE J 1034, AFNOR NF R 15-601, BS 6580: 1992 and motor vehicle manufacturer's specifications: BMW N 600 69.0, Daimler Chrysler 325.0 / 325.2, Deutz H-LV 0161 0188, MAN 324-NF, MTU MTL 5048, Opel / General Motors B 040 0240, Porsche for 924, 944, 968, 928, Saab 6901599, VW / Audi / Seat / Škoda TL 774-C. The replacement period of this type of antifreeze is three years.

Organic antifreeze (OAT) is an organic liquid for protection of cooling systems of motor vehicles from freezing and corrosion, based on monoethylene glycol of G12 + quality. It does not contain amines, phosphates, nitrites and silicates. The corrosion inhibitor package is based on organic acids. Meets the following quality standards: ASTM D3306 & D4656 / 4985, JASO M 325, RENAULT 41 01 001, BS 6580, John Deere H24B1 & C1, GM / OPEL 1940656 / 6277M, VolvoNATO S-759, PSA B715110 and motor vehicle manufacturer's specifications: VW G-12 engines spec: TL-774-D, MB 325.3, MAN 324-SNF, MTU MTL 5048, PORSCHE TL-774-D, FORD WSS-M79B44-D. The replacement period of this type of antifreeze is five years.

The ratio of antifreeze and water at the appropriate freezing temperature

Fluids for hydraulic braking systems of motor vehicles

Motor vehicle braking systems are the most important factor in driver safety, which is why there are very strict requirements that brake fluids must meet. These are, above all, high boiling points, good behavior at low temperatures, corrosion protection, adequate lubrication ability as well as compatibility with sealing materials.

In hydraulic braking systems of motor vehicles, fluids containing mineral oils (LHM - special fluid for the central hydraulics of Citroen vehicles) or fluids based on polyglycols and glycol ethers can be used as a medium for transmitting braking force. LHM fluid is used for those systems that are marked in green. It must not be mixed with other liquids or replaced with any other type of fluid.

The most widely used are brake fluids based on glycol ether and polyglycol with the addition of appropriate additives for protection against corrosion and oxidation. Their properties are defined by the following standards and specifications:

• ISO 4925
• SAE J 1703
• FMVSS 116 for DOT 3, DOT 4, DOT 5

The specifications of FMVSS 116 (Federal Motor Vehicle Safety Standard) for DOT 3, DOT 4, DOT 5 determine: change of viscosity at low temperatures, corrosion properties, resistance to temperature changes, oxidative stability, tendency to evaporation, behavior towards elastomers (seals) and resistance on the water.