Causes of Rusting in Crossed Roller Bearings and Corresponding Solutions

It is quite common for cross roller bearings to rust, and as a metal material, rusting is an inevitable phenomenon. The formation of rust can not only affect the operational accuracy of the bearing but, in severe cases, may even lead to bearing failure. Today, the manufacturer of cross roller bearings will provide you with a detailed introduction to the causes of rust in cross roller bearings and the corresponding solutions.

I. Causes of Rusting

1. Humidity

The level of humidity in the air significantly affects the rate of bearing corrosion. At the critical humidity level, the corrosion rate of metals is very slow; however, once the humidity exceeds this critical threshold, the corrosion rate suddenly accelerates. For steel, the critical humidity is around 65%. Due to poor air circulation in bearing manufacturing workshops, the heat generated during machining speeds up the evaporation of moisture from grinding fluids, cleaning solutions, and anti-rust agents into the air, causing the humidity inside the workshop to rise above 65%, and sometimes even reaching as high as 80%. This easily leads to corrosion of bearing components.

2. Temperature

Temperature also has a significant impact on corrosion. Studies show that when humidity exceeds the critical humidity level, for every 10°C increase in temperature, the corrosion rate roughly doubles. When temperature fluctuations are substantial, condensation formed on the bearing surface can greatly accelerate corrosion. During bearing manufacturing, both diurnal and ambient temperature differences can cause condensation on the bearing surface, leading to corrosion.

3. Hand sweat

Hand sweat contains corrosive substances such as lactic acid and sodium chloride. During bearing processing and assembly, if bearing components are handled directly with bare hands without promptly removing the sweat, "fingerprint corrosion" can occur. This phenomenon is particularly severe during the sweaty summer months.

4. Oxygen

During storage, oxygen can dissolve in water, and oxygen concentration gradients leading to corrosion are constantly visible. The solubility of oxygen varies depending on the specific location. When bearings are stacked, the middle area of the overlapping surfaces tends to have insufficient oxygen supply and lower oxygen concentration in the water, while the edges receive ample oxygen and have higher oxygen concentrations in the water. As a result, rust often forms around the edges of the overlapping surfaces.

5. Acid pickling and acid printing solution

During bearing manufacturing, pickling is commonly used to reveal defects such as burns, cracks, and decarburization. Some large bearings even require acid-etched numbering. After pickling or acid-etching, if bearing components are not thoroughly cleaned or adequately neutralized, they may rust. Additionally, contact between acidic substances and bearing components can also lead to corrosion.

6. Soot and dust

Soot contains large amounts of substances such as sulfur dioxide and carbon dioxide, which can cause corrosion of bearing components. Dust in the air settles on the product, altering the surface condition of the bearing and lowering its critical humidity. Moreover, dust readily absorbs moisture, serving as a medium for corrosion and leading to spotted rust.

7. Ventilation equipment

In summer, the air humidity is high. The ventilation equipment used in the factory blows large amounts of moisture and corrosive substances from the air onto the surfaces of bearing components. Moreover, the ventilation causes a drop in product temperature, leading to “condensation” and subsequently causing the bearings to rust.

8. Incomplete demagnetization

Because residual magnetism in the parts easily attracts iron filings and dust, and is difficult to clean thoroughly, they tend to absorb moisture, leading to bearing corrosion.

9. Contusion

During the grinding process, mechanical damage such as scratches and dents on bearing components disrupts the surface condition of the damaged areas, leading to rust formation on the bearing parts.

10. Residual salt

If salt-bath quenching is used, the residual salt on the workpiece surface after quenching is not thoroughly cleaned, making it prone to absorbing moisture and causing bearing corrosion.