Why does the bearing rust? What are the influencing factors?

1 flake embroidered yellow

It is characterized by large area, shallow depth, and easy discovery. The main cause of this rust is the presence of moisture, dust and SO2, H2S, CO2 and other gases in the atmosphere. In the hot and humid summer, especially in places with large air flow, this type of bearing is prone to be generated on the periphery of the bearing stack. Rust.

2 Honeycomb pitting

It is characterized by large lumps, prominent surface, loose yellow color, yellow rust on the surface, easy to wipe off, but honeycomb-shaped black rust pits under it. The main reason for this kind of corrosion is that the residual salt is not cleaned or the parts have water droplets.

3 Fingerprint rust

When holding NSK bearings and parts with bare hands, the sweat on the surface is caused by rust. There are lactic acid, sodium chloride, water, etc. in hand sweat, especially in summer, and the rust is in the shape of fingerprint rust.

4 Yellow seal rust

The characteristic is shallow depth, easy to wipe off with emery cloth, there is no rust pit scar after rubbing, the end face of the stacking ring is easy to produce this kind of yellow rust. The main working fluid has poor overlap, and the overlapped surface of the ferrule is corroded by the concentration difference caused by uneven inflation.

5 Black seal rust

It can be wiped off at first, but rust pits will be formed over time. This kind of rust is caused by poor neutralization after writing acid, or the acid liquid is stained on the product, or because the packaging paper has poor rust resistance, this black rust will be produced on the contact with the packaging box after being damp.

6 black points

There are many forms of black spots, which are characterized by small area and large depth. They are not easy to observe in sunlight, but can be seen clearly under lights or a magnifying glass. There is a kind of black spot that is only as big as a small needle tip, with a light outer color and a circular black hole in the middle. This kind of rust cannot be wiped off with general gauze. The reason for the black spot is that the surface of the part is stained with grinding wheel debris and cannot be cleaned, especially rubber. Grinding wheels and resin grinding wheel chips produce black spots faster.

7 Corrosion caused by bumps, scratches, abrasions, and blank printing

Defects caused by the "three scratches" (bumps, scratches, and abrasions) usually seen on the bearing surface should be distinguished from rust. However, the damaged part is particularly easy to cause rust, because the three wounds and the embryo print have wounds, the oxide film is destroyed by the negative potential and becomes the anode, and the non-sound becomes the cathode. At the same time, the three wounds are easy to be contaminated and accelerate electrochemical corrosion. Therefore, the wounds often turn black. For example, when working from the disk of a surface grinder, it is easy to cause the grinding wheel chip pad injury and produce small spots on the surface, which will become small black spots over time.