It is difficult to judge whether the bearing operates normally according to the color of grease. Because different greases have different internal additives, different operating conditions, and different temperature ranges, there can be no unified standard. Even the same grease may have different colors due to different batches and slightly different formulas. Therefore, it may be different based on color changes.
In addition, even if the grease is not placed in the bearing, it will change color. This is because the grease has oxidation problems.
The lubricating grease is placed (or operated) for a period of time due to contact with air; At the same time, metal (bearing itself, bearing housing and other related parts) also acts as a catalyst in this oxidation reaction. Although many greases now have antioxidant additives, they only reduce the rate of oxidation, so the color of greases will always change. If the bearing does not operate normally, or foreign matters enter, it will cause the performance and color of the grease to change. If the temperature is high, the grease will accelerate oxidation until carbonization turns into carbon black. The reason is that the change of the bearing itself or the ambient temperature will cause the base oil in the grease to continuously enter and exit the thickener. At the same time, each time the base oil returns, it may not return completely. After such a long time, the performance of the grease will change and will not meet the lubrication. The color of grease with insufficient base oil may change. The higher the temperature, the greater the performance change of the oil and the greater the color change. If the temperature is very high, it will carbonize, that is, it will turn dark brown.
If foreign matters enter the bearing, including the wear of the bearing itself or the metal chips produced by the friction between the foreign matter and the shaft and bearing chamber, the grease will then become close to or even the same color as the foreign matter.
When entering water or other liquids, its color will generally become lighter, sometimes it will become foam or flocculent.
