KEYWORDS

Antioxidants, Additive Depletion, Additive Degradation

STUDIES OF VARIATION IN THE OXIDATION INHIBITION OF BASE OILS - CONTINUATION OF AN ISOTHERMAL STUDY OF INNATE AND ADDITIVE-INHIBITED OXIDATION OF BASE OILS

Oxidation stability is well-known as an important property of almost all lubricants. Greater resistance to oxidation decreases the lubricant’s tendency to form undesirable corrosive byproducts.  Antioxidants are added to base stocks to influence their oxidation stability and operating life.  Understanding the influence of antioxidants on the useful life of a lubricant is helpful in both the choice of base oils and antioxidants. Three antioxidants, each at various concentrations in four base oils of increasingly natural oxidation resistance were selected for this work. A versatile bench test instrument was selected for measuring oxidation stability. The blends were oxidized in the presence of a catalyst in a special isothermal, high-pressure, high temperature reactor from which samples of the test oil or blend could be drawn at will for interim analysis during test. Interesting and unexpected differences were observed in the response of both the antioxidants and the base oils.

AUTHORS

Maria Manning, Theodore Selby, Jonathan Evans, William VanBergen, Savant Group, Midland, MI and Thomas Fischer, OelCheck GmbH, Brannenburg, Germany