LO 11-5 Describe and explain the classification, composition, and applications of various antifreeze formulations
1. Antifreeze Formulations
1.1. Type I: Conventional Low-Silicate Antifreeze
LO 11-05: Describe and explain the classification, composition, and applications of various antifreeze formulations. |
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Type I: Conventional Low-Silicate Antifreeze To protect cooling system materials, such as cast iron, aluminum, copper, brass, solder, steel, and many non-metallics like nylon and silicone, antifreeze contains corrosion inhibitors. Type I conventional antifreeze uses older additive technology and contains corrosion inhibitors such as boron, phosphate, and sodium silicate TABLE 11-4. These types of inhibitors are known as IAT and are identified by the green-colored coolant. Sodium silicate is primarily used to protect aluminum and is found in much higher concentration when used in gasoline engines with aluminum cylinder heads. A problem with sodium silicate in diesels, however, is its incompatibility with high levels of nitrite, which is added to antifreeze to protect cylinder walls from cavitation erosion. High concentration of both of these additives together will cause a condition known as silicate dropout Figure 33. Silicate dropout is characterized by the appearance of green “goo” or gel that plugs radiator and heater core tubes, leading to loss of adequate cab heat, overheating of the engine, and even catastrophic engine failure. For this reason, type I antifreeze is blended differently for gasoline and diesel engines, with much more silicate blended into gasoline engine antifreeze. |
FIGURE 11-33: Silicate dropout forms a green, gooey substance in the cooling system that blocks coolant tubes in radiators and heater cores. |
| TABLE 11-4: Type I Antifreeze Corrosion-Inhibitor Additives | ||||||||||||
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Type I additives deplete quickly and require monitoring. With time, many of the additive’s other components, such as phosphorous, drop out with the silicate, coating cooling system components with a layer of slime and mineral deposits. This is why it is important to drain and replace type I antifreeze containing this corrosion-inhibitor package every 2 years. To maintain the correct level of additives, type I coolant requires testing to ensure that the correct levels of nitrite and other inhibitors are also present.
Between 3–5% of DCA or SCA is added to type I antifreeze after the initial mixing of antifreeze and water to bring the additive package for diesel engines to the correct protection level Figure 34. Monitoring of the additive package using test strips is necessary at every service to maintain the correct levels of the various corrosion inhibitors Figure 35 and Figure 36.
FIGURE 11-34: This bottle of liquid additive is added to approximately 1 gallon (4 liter) of type I coolant to properly condition the coolant. Note the dried silicate around the cap of the bottle. |
FIGURE 11-35: Test strips are used to measure the levels of various cooling system additives. This test strip measures the levels of nitrite and molybdates, another type of corrosion inhibitor, in antifreeze. |
FIGURE 11-36: This test strip checks the nitrite levels in either type I coolant or ELC. A different scale located on the side of the bottle is used for each type of antifreeze. |
| Technicians Tip | ||
| Silicate, phosphates, and borates used as corrosion inhibitors are dissolved solids. In time, they crystallize and fall out, or precipitate out, of the glycol and water solution. These crystals can enter the area between the water pump shaft and the seal, acting as an abrasive and causing premature wear of the seal. The result is a coolant leak from the weep hole of the water pump. |
| Technicians Tip | ||
| Type I antifreeze for diesel engines is different from type I antifreeze for gasoline engines, and the two should never be interchanged. Gasoline engines use type I antifreeze that contains higher silicate levels. Only low-silicate antifreeze should be used in diesel engines because the addition of nitrite to diesel coolant to minimize cavitation causes silicate dropout, which can lead to plugged radiators, leakage from the water pump seal, and overheated engines. |
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