1. Antifreeze Formulations

1.2. Extended-Life Coolant

LO 11-05: Describe and explain the classification, composition, and applications of various antifreeze formulations.

 

Extended-Life Coolant

Given the high maintenance requirements of type I antifreeze and its short 2-year service interval, manufacturers have sought to develop new coolant technology to minimize cooling system maintenance and extend the service interval. To achieve this, a new category of antifreezes, called extended-life coolant (ELC) or LLC , have been developed with corrosion inhibitors made from organic acids. TMC classifies these coolants as types II–IV. Types II–VI coolants use OAT additives, which do not deplete in use. The other type of additive package used by ELC’s type V and VI is nitrited/nitrated organic acid technology (NOAT). Generally, OAT and NOAT coolants do not require an initial charge of DCA or SCA because they are fully formulated. This means any required additives are incorporated into the antifreeze–inhibitor solution during manufacture TABLE 11-5. The corrosion inhibitors in these types of ELC antifreezes are designed to last 600,000 miles (965,600 kilometre [km]) on-road or 12,000 hours off-road. However, a coolant extender that contains nitrite for protection against cavitation erosion may be added Figure 37. This must be added only once at 300,000 miles (482,800 km) or 6000 hours, which is about halfway through the antifreeze’s service life, if a longer service life is expected.

   Fig11_37

FIGURE 11-37: The use of an extender additive package halfway through an ELC’s service life can lengthen the time that LLC remains in service.

 

  TABLE 11-5: Type II Antifreeze Additives and Their Purposes  
Type II Antifreeze Inhibitor Protects
Potassium soap of dibasic carboxylic acid
  • Iron
  • Solder
  • Aluminum
Potassium soap of monobasic carboxylic acid
  • Aluminum
  • Iron
Nitrite
  • Cast iron
  • Steel
Molybdate
  • Iron
Tolyltriazole
  • Copper

 

Compared to antifreeze with IATs, OAT antifreeze has the advantage of being more chemically stable, which allows for exceptionally long service intervals. OAT uses carboxylate acids, which are neutralized versions of acids containing carbon. OAT is free of nitrite, nitrate, phosphate, silicate, and borate corrosion inhibitors. The formulation provides maximum protection of the six basic metal alloys found in most cooling systems. Because the OAT coolant generally contains no phosphates or silicates, deposits in the cooling system are almost eliminated. Without the IAT additives that can form into abrasive solids that are dissolved in antifreeze, the use of OAT results in improved water pump seal and impeller life.

  Technicians Tip  
  While technicians must carefully select the type of antifreeze recommended by manufacturers when topping off or changing coolant, it is helpful to note where type II and type IV coolant technology is used. For North American diesel engine manufacturers, type IV antifreeze, which is red in color, is generally preferred. Detroit Diesel and other European engine manufacturers prefer coolants with no dissolved solids, particularly phosphate. This explains why those engines generally require purple-colored type II coolant.  

 

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