Sodium chromate provides a source of alkaline chromate. The alkaline chromate leads to the formation of a protective layer on metal surfaces that helps to minimize corrosion action. Disodium phosphate aids in maintaining the alkalinity of the coolant. The term used to identify the alkalinity of the treated cooling water is pH. The pH unit does not measure alkalinity directly; however, it is related to alkalinity in such a way that a pH number gives an indication of the alkalinity or acidity of the cooling water. The alkalinity of the coolant allows the chromate to retain its effectiveness as a corrosion inhibitor. Chromate will not protect aluminum or prevent scale deposits.

Soluble Oil

Soluble oil is a corrosion inhibitor which when properly added to the water in an engine cooling system provides a protective film on metal surfaces. The protective film helps minimize the effects of corrosion. When an insufficient amount of soluble oil is present in the engine cooling system, adequate corrosion protection will not be provided.

The normal concentration of soluble oil is between 1 and 2 percent. For each 100 gallons of coolant capacity for an engine, you would use only 1 gallon of soluble oil. (You should mix the oil with distilled water before adding it to the engine.) When used in amounts in excess of 2 percent, soluble oil can cause an insulating film to form on heat transfer surfaces. This oil film will restrict heat transfer and cause an otherwise normal running engine to overheat. A high level of soluble oil may also result in separation of the oil from the water. This condition will reduce the effectiveness of the oil to prevent corrosion in the cooling system of the engine. It should be noted that although soluble oil is used for the prevention of corrosion, it will not prevent or eliminate scale deposits.

NALCOOL 2000

NALCOOL 2000 chemically protects all metals in the cooling system from corrosion and cavitation-erosion while simultaneously preventing harmful mineral scale deposits. It is buffered so that it neutralizes the acids that are formed in the cooling system. NALCOOL 2000 stops cavitation in three ways: (1) by forming a physical barrier (a chemical film); (2) by preventing corrosion of the metal surface, thus strengthening its resistance to cavitation; and (3) by reducing foaming, which means less air entrapment, a major cause of cavitation. Ships that are authorized to use NALCOOL 2000 must use inhibited antifreeze (MIL-A-46153) when freezing protection is required. Although inhibited antifreeze contains some corrosion inhibitors, your ship must use NALCOOL 2000 with inhibited antifreeze to ensure adequate corrosion protection. Diesel engines that require the NALCOOL 2000 treatment are particularly susceptible to cavitation corrosion of the cylinder liners if this treatment is not used.

NOTE: When you are making the con-version from NALCOOL 2000 to the required inhibited antifreeze/NALCOOL 2000 combina-tion, you must first dump the cooling system.

You must dilute the antifreeze with water in the cooling system before adding the NAL-COOL 2000. Do not combine concentrated antifreeze and NALCOOL 2000, as the inhibitor chemicals will become insoluble and separate from the solution.