SEDL / STP / STP1192-EB / STP25161S

Phosphate-Molybdate Supplement Coolant Additives for Heavy Duty Diesel Engines

Hudgens, RD
Senior staff chemist, Fleetguard, Inc., Cookeville, TN

Pages: 21    Published: Jan 1993

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Abstract

Supplemental coolant additives (SCAs) are commonly used in heavy duty diesel service. The SCA boosts the performance of the typical antifreeze coolant and replaces additives lost to depletion and coolant dilution.

In the early 1970s chromate based SCA's were phased out because of chromate's toxicity and adverse environmental impact. Borate-nitrite based SCAs replaced the chromates and are widely used today.

This paper describes the development of a third generation phosphate-molybdate additive package. Relative to the borate-nitrite SCAs, the phosphate-molybdate supplemental coolant additive gives better overall aluminum protection. Furthermore if overtreated, it is less likely to cause solder bloom, silicate gelation, and water pump leakage.