

| Subject: | Coolant compositions. |
| From: | Dan Houg |
| Date: | Fri, 6 Oct 1995 09:35:08 CST6CDT |
The following info from Prestone Corp.: TYPICAL NORTH AMERICAN COOLANTS -phosphate and/or borate -high silicate -nitrate -triazole -antifoam -pH 10.0-10.5 TYPICAL EUROPEAN COOLANT -benzoate -borate -silicate -nitrate -triazole -antifoam -pH 8.0-8.5 PRESTONE Antifreeze -phosphate -borate -silicate (high) -nitrate -tolyltriazole PRESTONE LONG LIFE 4/60 -organic acids -silicate (low) -tolytriazole -nitrate -molybdate Here is the formula of a typical antifreeze coolant concentrate that is safe for aluminum components: Wt. % ethylene glycol 95.56 sodium nitrate .10 sodium molybdate .20 sodium tetraborate .40 sodium silicate solution .30 phosphoric acid .15 MBT (50% solution) .50 TT (50% solution) .20 sodium hydroxide .235 water 2.30 polyalcohol .05 dye .005 MBT (mercaptobenzothiazole) is a corrosion inhibitor for copper or brass. TT (tolytriazole) provides protection similar to MBT, but TT is more durable at higher temperatures. Nitrates are corrosion inhibitors for ferrous surfaces, and protect from pitting and crevice corrosion. Silicates inhibit corrosion on hot aluminum surfaces, and provide protection from cavitation. Silicates also act as general purpose chemical buffering agents. Borates provide buffering and neutralizion of acidic and sulfurous combustion gas by-products. Sodium hydroxide helps stabilize pH. Silicones are antifoam agaents which also slow the silicate reaction with magnesium. Polyalcohol supresses the formation of foam. Phosphates provide general purpose protection for several metals and are effective in preventing the cavitation-erosion damage of aluminum. -dan
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