Inhibited ethylene glycol antifreeze (MIL-A- 46153) must be added to the freshwater cooling systems of engines that are subjected to freezing temperatures.

Inhibited antifreeze consists of ethylene glycol and corrosion-inhibiting chemicals. A mixture (solution) of ethylene glycol and water has a lower freezing point than either water or ethylene alone. Thus, treating a cooling system with a mixture of 50 percent antifreeze and 50 percent water provides freeze protection against temperatures down to -30F. If conditions are such that additional freezing protection is needed, up to 67 percent antifreeze can be used. This mixture provides freeze protection down to -77F.

The corrosion inhibitors in the antifreeze will protect the metals from corrosion. They also provide an alkaline buffer which neutralizes acidic by-products that result from combustion blow-by gases that leak into the coolant system. Do not use antifreeze concentrations that are less than 33 percent, because this concentration will not contain a high enough percentage of corrosion inhibitors to provide adequate corrosion protection.

NOTE: Use only MIL-A-46153 inhibited anti-freeze.

This antifreeze is labeled U.S. GOVERN-MENT PROPERTY, ETHYLENE GLYCOL, ANTIFREEZE. The label also contains the stock number. Verify that the stock number matches the appropriate number (depending on container size) given in Naval Ships Technical Manual, chapter 233. Remember, different brands of commercial antifreezes are formulated with different corrosion-inhibiting chemicals which may or may not be effective for your ship. The different inhibitors may be incompatible with each other and with the inhibitors in MIL-A-46153 antifreeze. In addition, the required antifreeze test procedures will produce accurate results only for coolant treated with MIL-A-46153 inhibited antifreeze.

CAUTION

NEVER use antifreeze concentrations greater than 67 percent; otherwise, the following situations will occur:

1. Less freezing protection will be pro-vided. Pure antifreeze freezes at 9F.

2. The engine may overheat, because ethylene glycol has a lower heat capacity than water.

Antifreeze is not compatible with either soluble oil or sodium chromate. For conversion from chromate or soluble oil to antifreeze or vice versa, it is essential that the cooling system be thoroughly flushed for complete removal of all treatment chemicals.