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Technical Paper

Advanced Coolant for a New Aircraft Liquid Cooled Piston Engine

A new liquid cooled gasoline powered aircraft piston engine has been introduced to the General Aviation marketplace. To achieve additional benefits of liquid cooling, higher coolant operating temperatures are incorporated. Initial aircraft operating experience with the initially selected commercial ethylene glycol based coolant using traditional inhibitor packages resulted in excessive radiator core plugging. A program was initiated to determine the cause for the radiator plugging and identify solutions. Another commercially available ethylene glycol based coolant with a revised inhibitor package was selected as a promising solution. Evaluation of the coolant has been conducted resulting in significantly reduced deposit formation.
Technical Paper

Corrosion Mechanism of High Lead Solder and Correlation to Dissolved Oxygen

High lead solder coupons are frequently tested in ASTM D 1384-87 and D 2570-91 tests to determine the corrosion protection provided by engine coolants. In contrast to 70/30 solder, high lead solder is often observed to show relatively high corrosion rates in D 1384-87 testing. Surprisingly, the high lead solder corrosion rates tend to be lower in the D 2570-91 test, despite the longer duration of this test. The basis of this effect has been investigated in different coolant formulations and in both ethylene glycol and propylene glycol. The corrosion of high lead solder was found to be directly related to the presence of oxygen in the D 1384-87 test. Replacement of the air purge with a nitrogen purge significantly reduced the corrosion rate of high lead solder in inhibited coolants. These results are interpreted in terms of the solder composition.
Technical Paper

Long Life Performance of Carboxylic Acid Based Coolants

An inhibitor package which is silicate-, nitrate-, borate- and phosphate-free has been developed as the basis for a world-wide automotive coolant formulation. The formulation contains aliphatic mono- and dicarboxylic acids and tolyltriazole as the sole inhibitors. Formulations containing carboxylic acid inhibitors have been studied in ASTM bench tests and found to sufficiently protect all prevalent cooling system metals. In addition, fleet tests have shown that carboxylic acid inhibitors deplete much more slowly than conventional inhibitors, making possible a much longer life coolant. Results from laboratory tests which simulate extended usage indicated that carboxylic acid-containing coolants have a significantly longer life span for the protection of all cooling system metals. Finally, the carboxylic acid/tolyltriazole inhibitor package is completely adaptable to a propylene glycol base.
Technical Paper

Monoacid/Diacid Combination as Corrosion Inhibitors in Antifreeze Formulations

The traditional methods of protecting aluminum surfaces in automotive cooling systems are under scrutiny because of problems caused by high levels of certain inhibitors, particularly silicate, and the lack of protection against crevice corrosion. This paper discusses new monoacid/diacid inhibitor technology which improves protection of aluminum, increasingly used in automotive engines, and it also extends the useful life of the automotive engine coolant.