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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.

Various unleaded gasoline formulations and gasoline components obtained from refinery streams were evaluated for their deposit forming tendencies in several multicylinder automotive engines. A pair of GM 2.0L engines equipped with throttle body fuel injection and a GM 1.8L equipped with an electronic feedback carburetor were utilized to determine fuel property effects on intake valves, cylinder head, and piston top deposits. Engine performance with respect to octane requirement increase was measured. Various analytical techniques were used to study a variety of fuel properties. Analyses of gasoline formulations and related fuel components such as light reformate, motor alkylate, benzene raffinate, and light catalytically cracked refinery streams were accomplished. Gas chromatography-mass spectrometry (GC/MS) and flourescence indicator absorbance (FIA) analysis were performed on these fuels to determine their composition.

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.

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.

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.

An initial investigation into the effects of combustion chamber deposits (CCD) on tailpipe exhaust emissions has been completed. Four different model vehicles were evaluated for tailpipe emissions at four different deposit conditions. The deposit levels included a baseline clean level, a condition after deposit accumulation, a condition after CCD removal and finally a reevaluation after disassembly and mechanical clean up of the entire intake system. A special rig was developed using a walnut shell blasting device to allow cleaning of CCD without disturbing other engine deposits and without disassembly of the engine. This approach was taken to eliminate numerous time related variables and focus on the effects of CCD removal. The results of this investigation confirm that directionally HC, CO, and Nox all increased after the deposit accumulation period and decreased with the removal of CCD. However, statistically only Nox emissions increased significantly at the 90% confidence level.

An investigation of the clean-up effects of a Combustion Chamber Deposit (CCD) detergent additive package on tailpipe exhaust emissions was conducted using (6) 1992 2.3L vehicles. Part one of this program was a deposit build-up phase for all cars and part two included two phases where, in the first phase, one-half of the cars were operated with the CCD detergent package and the other half were run as a control on the build-up fuel. In the final phase, the fuels were switched between the sets of vehicles to compensate for any vehicle to vehicle differences. A gasoline containing a detergent package which provided port fuel injector (PFI) and intake valve deposit (IVD) cleanliness performance in accordance with California Air Resources Board (CARB) requirements was used as the deposit build-up fuel for part one and as the control in part two. This fuel is typical of many gasolines that are in the market place today.

Field-test samples cut from radiator tubes in two 1990 Chevy Luminas (3.1L engine) after 100,000 miles were analyzed to determine corrosion layer differences. One car used a carboxylic acid-based inhibitor technology (C1). The other car used a conventional coolant (C2). X-ray photoelectron spectroscopy (XPS) analysis of the two samples was performed. Results indicate a significant difference between the two samples. The C1 sample had a thin (<60Å) organic coating bound to the aluminum alloy surface, while the C2 sample had a much thicker (>1000 Å) silicate-rich layer. This resulted in the C2 sample exhibiting “surface charging” behavior. These results relate directly to the metal/insulator (conductor/insulator) characteristics of the two samples, and imply that the heat transfer of the protective coating provided by the carboxylate technology (C1) is significantly better than that of traditional inhibitor technology (C2).

Polyurea RIM, because of its production speed, internal release characteristics, high temperature dimensional stability and increased resistance to water absorption, has arrived at the forefront of RIM technology as a better route to producing automotive body panels. In this paper we will discuss the use of inexpensive fillers, in particular, sized wollastonite, in polyurea body panels. In addition, a new polyetherpolyamine for body panel applications will be discussed. We also studied the effect of postcure conditions on high temperature stability of body panel formulations.