From a thermodynamic point of view, compared with its corrosion products, bearings have higher energy, are unstable, and have a tendency to spontaneously transform into low-energy corrosion products, that is, bearing corrosion is a natural phenomenon. The vast majority of INA bearings in the industry are multi-component alloys with different metallographic structures, impurities, uneven machining deformation, uneven stress distribution, etc. These physical, chemical and electrochemical inhomogeneities, when When the surface encounters a corrosive medium or a water film is formed on the surface, chemical or electrochemical corrosion will inevitably occur.

External factors of bearing corrosion

1. relative temperature

The higher the relative humidity in the air, the thicker the water film on the bearing surface, and the oxygen in the air penetrates the water film and acts on the bearing surface. When the relative humidity reaches a certain value, the corrosion rate increases significantly. This value is called the critical relative humidity. The critical relative humidity of steel is about 70%.

2. The effect of temperature

Ambient temperature is related to relative humidity. In a dry environment (desert), the bearing will not easily corrode no matter how high the temperature is. When the relative humidity reaches a critical value, the effect of temperature is significantly intensified. For every 10°C increase in temperature, the corrosion rate increases twice. Therefore, in the wet tropics or rainy season, the higher the temperature, the more severe the rust.

3. The effect of oxygen

The rusting process is represented by the following reaction equation:

Fe+H2O→Fe(OH)2

Fe(OH)2+ H2O+O2→Fe(OH)3

Fe+ H2O+O2→Fe(OH)3

It can be seen that without water and oxygen, the INA bearing will not rust. 20% of the volume in the air is oxygen, which is pervasive.

4. Effects of other substances in the atmosphere

When the atmosphere contains salt spray, sulfur dioxide, hydrogen sulfide and dust, corrosion will be accelerated. Therefore, the difference in the size of corrosion under different environments is obvious. The city is higher than the countryside; the industrial area is higher than the living area; the coastal area is higher than the inland; High dust is higher than low dust.

Corrosion factors during processing

Raw materials are corroded and cannot be removed after processing; process materials such as cutting fluids and lubricants have been contacted during processing; improper neutralization and cleaning after pickling; heat treatment oxidation decarburization or residual salt cleaning is not clean; inspection, handling and assembly operations hand sweat left by the operator; improper stress relief or dehydrogenation annealing; inappropriate rust prevention between processes and storage, etc.