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Causes of discoloration of Grease caused by bearing clearance
Jul 11, 2018

Grease discoloration occurs in bearings, even if it is not placed in bearings. 

This is because: first, grease exists oxidation problem. Grease is placed (or run) for a period of time and has a lot of contact with oxygen, and the metal (bearing itself) acts as a catalyst in this oxidation reaction. Therefore, oxidation should also be taken into account when calculating the interval of supplementary grease in bearings. Many greases now have antioxidant additives. That doesn't mean it won't be oxidized. 

Second, the operation of the bearing itself, temperature (bearing itself, or the environment) will change, which leads to the base oil in the grease in and out of the thickener, at the same time, each time the base oil back, not necessarily completely back. After such a long time, the performance of the grease will change, will not be able to meet the lubrication, so re-apply lubrication. The color of grease with insufficient base oil is likely to change. Also, if the temperature is abnormal, the performance of the grease changes greatly, so, there will be discoloration. If the temperature is high, it will carbonize. The color will get darker. 

Third, during the operation of the bearing, the inside of the grease mixed with impurities. The impurity may have been peeled off by the bearing itself or entered by the outside world. May be solid, may be liquid, these will affect the grease properties.

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