It may be due to poor rust prevention treatment of the bearings, or it may be due to corrosion caused by moisture, as well as rust caused by paint mist.

There are four important types of acid components that volatilize from insulating paints used in most motor factories:

① Acid composition of unreacted low molecular paint raw materials (anhydrous isophthalic and terephthalic acid, anhydrous maleic acid, trans-butenic acid)

② The acid component generated during the curing of the paint (when using phenolic modified paint, it changes from formaldehyde water to formic acid

③ Inherently lower fatty acids (formic acid, acetic acid) are decomposed by heat or oxidation

④ The acid component formed after the water decomposition of the paint solidification product. The important acid component produced by insulating paint is formic acid. There is a close relationship between the amount of formic acid and the degree of corrosion

"Grease absorbs the acidic elements that evaporate from the paint, causing the grease to deteriorate. Moreover, these acidic elements promote the hydrolysis of the grease, increasing the concentration of the acidic elements and causing bearing rust.".

The mission of grease is to control the grease layer to separate the steel ball from the inner and outer raceways. The manufacturer of the bearing retainer sleeve controls the viscosity characteristics of the grease. By separating the metal interface between the steel ball and the inner and outer raceways on the surface of the steel ball and raceway, it increases the wear of the metal profile and protects the wing metal from atmospheric and moisture corrosion, reduces vibration and noise, and enables the bearing to roll smoothly.

However, after the lubricating grease deteriorates, its viscosity will change, the oil film will break through, and the separation function and adhesion characteristics of the lubricating grease will disappear. One result of this is that the acidic components generated by the insulating paint directly oxidize the metal profile, causing bearing corrosion. The second is that the steel ball directly contacts the inner and outer raceways, causing wear and tear when changing, resulting in increased noise.

Cleaning is very important for partial bearings in bearings. The surface roughness of the rotating surface of the bearing ring and the rolling element is usually 1/10 μ m. Such a smooth surface is very sensitive to damage caused by contaminants. The lubrication layer between the rotating surfaces is typically 0.2 to 1 μ m. Particulate impurities larger than the lubricant particle size can be excessively rolled by rolling elements, resulting in local pressure in the bearing steel, ultimately leading to material fatigue. In addition to this, the size of dust particles in the external environment can reach 10 μ m. It can also cause damage to the bearings. Therefore, a clean and dust-free environment is crucial for the storage and installation of bearings.