test cups. SiC, Si3N4 and AI2O3 ceramics have shown similar, no, or very low catalytic action. It should be noted that small amounts of iron contamination in ceramics such as SiC will show some catalytic action on both oxidation steps.

The standard Penn State Microoxidation Tests have been conducted with a low carbon steel test cup and a series of motor oils, aircraft gas turbine oils, and phosphate esters to establish a relative order of oxidative stability.

Microoxidation test results on Table 3 show that typical SF-CC and SF-CD motor oils undergo substantial oxidative degradation (about 3.0 percent) in a 30 minute test at 225°C. The aircraft gas turbine oils, on the other hand, have a stable life of about 30 minutes under these same

Table 3

Oxidation Characteristics ot Several Lubricants After 30 Minutes at 22SC in the Penn State Microreactor Unit


8ama Molao. Wt.

High Mol. Wl.

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