stainless steel rust
In daily life, stainless steel is a common material, which is widely used in many fields such as kitchenware, building materials, and auto parts. Compared with ordinary steel, the biggest feature of stainless steel is that it is not easy to rust. However, when you see brown rust spots on the surface of stainless steel, you may wonder: Why does “stainless steel” rust? If it rusts, is it still “stainless steel”?
Stainless steel is also called stainless acid-resistant steel. As the name suggests, it will not rust like ordinary steel, and it can also withstand corrosion from chemical media such as acids, alkalis, and salts. So, how is this done?
Stainless steel is mainly composed of iron, chromium, and nickel, as well as a small amount of carbon and other trace elements. The main reasons why stainless steel is not easy to rust are as follows:
The first is the role of chromium, chromium is a key element of stainless steel rust resistance. Chromium in stainless steel is more easily combined with oxygen than iron, forming a dense oxide film Cr2, which can cover the surface of the steel and prevent further contact between iron and oxygen.
In addition, this oxide film also has the ability to self-repair. Even after being damaged, as long as it is exposed to air, chromium can still react with oxygen to repair itself and re-form a “chromium-rich passivation film.” This is the secret of stainless steel tableware is not easy to rust and acid and alkali resistance.
Of course, this protective film will also be destroyed under certain conditions, so stainless steel is just not easy to rust, but it is not “stainless” under any conditions.
There are many reasons why stainless steel rusts, the most common of which is chloride ion corrosion. Chloride ions, due to their small radius, can easily penetrate and destroy the passivation film on the surface of stainless steel, allowing iron atoms to come into contact with oxygen and be oxidized to Fe2+. Fe2+ then combines with Cl– to form FeCl2, which then hydrolyzes to produce hydrogen ions, which continue to react with Fe to produce Fe2+, causing corrosion to continue.
Avoid stainless steel products and strong acid, alkali, salt and other corrosive substances long-term contact. These substances may destroy the passivation film of stainless steel and cause rust.
Although stainless steel is corrosion resistant, the surface is easy to be scratched, and the scratch may become the starting point of corrosion. Use and handle with care to avoid collision or friction with hard objects.
Although stainless steel is corrosion resistant, the surface is easy to be scratched, and the scratch may become the starting point of corrosion. Use and handle with care to avoid collision or friction with hard objects.
Try to avoid exposing stainless steel products to high temperatures for a long time, because high temperatures may affect the corrosion resistance of stainless steel.
Stainless steel products should be placed in a dry, ventilated environment when stored to avoid humidity and corrosive gases.
By following these precautions, you can effectively extend the service life of stainless steel products and maintain their beauty and performance.
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