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Why do bearings corrode and rust?

Aug 01, 2022

Q1: Will chrome steel(GCr15) bearings rust? Will stainless steel bearings rust?

A1: Chrome steel(GCr15) bearings will rust and corrode, stainless steel bearings will also rust and corrode. Although in the usual concept, stainless steel will not rust. But in fact, stainless steel will. There is no steel in the world that does not rust.

Q2: How does stainless steel rust and corrode?

A2: The so-called stainless steel means that the degree of corrosion resistance is different. If the corrosion rate is less than 0.01mm/y, the steel is considered to be "completely resistant to corrosion"; if the corrosion rate is <0.1mm/y, the steel is considered to be "corrosion-resistant"; if the corrosion rate is greater than 0.1mm/y, the steel is considered to be "intolerant". eclipse". The steel with corrosion rate > 0.1mm/y is what we usually call general steel.
Except for a small part of stainless steel bearing steel, most of the bearing steel is ordinary corrosion-resistant steel, so it is not surprising and normal to rust.

Q3: Why does the bearing rust?

A3: Bearing rust is related to material and use environment. Because the bearing steel itself contains carbon, it will react when it encounters water vapor, so in the environment of high humidity, the bearing steel is easy to rust. To prevent the bearing from rusting, it is necessary to do a good job of anti-rust treatment. Or choose non-steel bearings. Similarly, metal products are prone to rust after oxidation, and stainless steel bearings are no exception.
There are many factors that affect bearing rust: such as the chemical composition and structure of the metal material itself; surface finish; the composition and pH value of the solution in contact with the metal surface.These are the direct factors that cause the bearing to rust and corrode.
In addition, when using the bearing, do not directly touch the object with your hands, because when sweat comes into contact with the bearing, a sweat film will be formed on the surface of the bearing, and the sweat film will cause electrochemical action on the bearing and corrode the bearing. Therefore, we need to use special tools such as special gloves or finger cots to pick up the bearings, and do not touch them directly.

Q4: Will bearings made of GCr15 chrome steel rust in outdoor environments?

A4: Yes, and it will rust badly like bearing which made of the general steel. The Cr content of this steel is too small. The value behind the bearing steel is the Cr content, and the unit is 1/1000. The Cr content of GCr15 The amount is only about 1.5%. If the Cr content can be close to the dividing line of 13%, the rust prevention effect will be better. For example, steels such as Cr12 (containing about Cr12%) are basically not rusted.

Q5: Can chrome steel (GCr15) prevent rust and corrosion?

A5: The Cr in chrome steel (GCr15) is to improve hardenability and not to prevent rust and corrosion. Like general metals, humid environments can cause rust. Therefore, anti-rust measures for bearings and their parts are still very necessary.

Q6: How to prevent bearing rust and corrosion?

A6: There are two simple ways to prevent bearing rust and corrosion.
Method 1: Apply anti-rust oil. Small bearings can be immersed in anti-rust oil, so that a layer of oil film is attached to the surface to achieve the effect of anti-rust. Also, you can choose the way of brushing. However, it should be noted that when brushing, it is necessary to apply the anti-rust oil evenly on the bearing surface, so as not to accumulate, and pay attention to prevent leakage. When the immersion method is not suitable for some large ones or it is inconvenient to use the brushing method, the spraying method can be used. Generally, spraying is carried out in a place with fresh air with filtered compressed air with a pressure of about 0.7Mpa.The spray method is suitable for solvent-diluted anti-rust oil or thin-layer anti-rust oil. This method must adopt perfect fire protection and labor protection measures.
Method 2: Choose different materials. In environments where extreme corrosion resistance is required, ceramic bearings can be selected.
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