While the oxidation of graphite in gaskets is a well known phenomenon it is often poorly quantified and the factors affecting it not always well known. There are some standard tests that can be used to determine graphite quality. While many of these material standards concentrate on the compositional impurities (sulfur, chlorides etc.) and the ash content; these are indicative of other properties and they are no real indication of oxidation performance. Recently, some test methods have been published that suggest a method for measuring oxidation performance; however, they have some shortcomings or constraints.
Using modern, standard TGA (ThermoGravimetric Analysis), the work presented in this paper aims to provide a more detailed standard test that can be used to measure the oxidation rate of graphite in flowing air for a given set of time and temperature conditions. The paper will show what other conditions are critical and which are less significant in specifying a standard test. This will lead to the presentation of a suggestion for an improved standard test that builds on and further codifies the tests currently published.
Finally, this paper will show the oxidation rates of a variety of different commercial graphite grades to illustrate the vast range of oxidation rates that are possible from the various grades of graphite.
APPENDIX: TABLES OF ASTM STANDARD TEST METHODS FOR PETROLEUM AND PETROLEUM PRODUCTS
