What are the reasons for the deterioration of grease? Today Xiaobian answers this question for you and comes to understand it.
There are two main reasons for grease deterioration: on the one hand, chemical changes, such as oxidation of base oil and a large amount of oil, and the composition of additives in the effective components of the reduction, etc. On the other hand, physical changes, such as the thickening of lubricating grease increase or decrease, drop point decline, and so on. The speed of deterioration is the basis for determining the service life of lubricating grease.
Lubricating grease is heated in the course of use to promote its oxidation and deterioration reaction, so that the viscosity of base oil increased, acid value increased, oxides increased, thickener structure damage, resulting in softening grease and a large number of oil and shorten the service life. Similarly, there is also hardening due to oxidation deterioration, from the surface of the metal, grease can no longer be used. Therefore, in order to suppress or prolong the thermal oxidative deterioration of lubricating grease, it is necessary to add antioxidant additives.
The grease is often in the process of being sheared when it is rubbed and stirred mechanically. The consistency decreases in different degrees according to its shearing stability. The structure of the grease is destroyed by random mechanical stirring, which leads to softening and a large amount of oil separation. At the same time, the centrifugal force produced by the high-speed rotation of the journal is produced. It also makes it easy for the base oil to take a lot of oil and grease to harden and not to be used.
Effect of moisture
Moisture can emulsify and deteriorate some lubricating oils, such as sodium-based grease, and even affect the corrosion of metal parts in use. Water can also accelerate the oxidation and deterioration of lubricating oils, which will help to soften the grease and increase the consistency. Some test results indicate that even the moisture content of 0.01% is bad for bearing.
Effects of harmful gases
Some breaking or alkaline gases deteriorate the grease used in the bearing and corrode the bearing, especially in the presence of moisture, further accelerating the deterioration of the grease and increasing the corrosion of the bearing.
Influence of vacuum degree
High vacuum has a great influence on the evaporation of lubricating grease, at the same time, the friction coefficient increases significantly and even causes the sintering of friction surface. Therefore, silicone oil should be used as base oil in high vacuum.