ISO/WD 25607

Testing of greases — Determination of oxidation resistance of greases — Determination of temperature dependent oxidation induction time for calculation of the Arrhenius activation energy of thermo-oxidative degradation

Scope

This document specifies a method for the accelerated determination of the Arrhenius activation energy of the thermo-oxidative degradation of lubricating greases in contact with catalytically active metallic materials and catalytically inactive glass. Knowledge of the Arrhenius activation energy is a prerequisite for the determination of the grease service life under a known temperature spectrum of an application. The calculation of the Arrhenius activation energy is based on the determination of the oxidation induction times from measurements at minimum two different elevated temperatures. The oxidation induction times are determined by the inflection point of the pressure curve by tangent-intersection method. This inflection point corresponds to the complete depletion of the antioxidant reservoir and the failure of specified grease properties.