Why Does the Stainless Steel Pull Handle Rust?

People are surprised when the stainless steel pull handle has brown rust spots on the outside. They have always believed that stainless steel will not rust. If its surface is rusted, there is something wrong with the stainless steel material. In fact, this is a misunderstanding caused by a lack of understanding of stainless steel materials. Stainless steel will also rust under certain conditions.

Stainless steel has  the property of resisting oxidation----that is rust resistance. At the same time, it also has the property of resisting corrosion in the medium containing acid, alkali and salt----that is corrosion resistance. Its rust resistance and corrosion resistance will change with the chemical composition of the steel itself, the additive state, the operating conditions and the type of environmental media. For example, 304 stainless steel pull handle, used in a dry and clean environment, has excellent anti-rust ability. If you move it to a coastal area, its surface will quickly rust in the salty sea fog.  However, the 316 stainless steel pull handle performs well. Therefore, stainless steel is not resistant to rust and corrosion in  all environments.

The surface of stainless steel has a fine, stable chromium-rich oxide film (protective film). This thin protective film can prevent the continuous entry of oxygen atoms and prevent continuous oxidation, thereby avoiding rust on the surface. Once for some reasons, this protective film was damaged. The oxygen atoms in the medium will continue to enter the surface. The iron atoms in the stainless steel will continue to separate out, forming loose iron oxide. As a result, its exterior is subject to constant rust. There are many forms of membrane damage. The most common forms in life are as follows.

1. When the stainless steel pull handle surface accumulates dust containing other metal elements or attachments of dissimilar metal particles, its surface may be corroded. In a humid air environment, the condensed water between the attachment and the stainless steel connects the two into a micro-battery, triggering an electrochemical reaction. The protective film is damaged. We will call this electrochemical corrosion.

2. If the stainless steel pull handle surface is accidentally stuck with some juice (such as vegetables, soup, phlegm, etc.). Acidic substances are formed in the presence of water and oxygen. Acidic substances adhere to the surface of stainless steel for a long time will cause corrosion.

3. If the medium containing acid, alkali and salt substances adheres to the surface of the stainless steel handle, it will cause local corrosion. (such as lye water used to decorate walls, splashed lime water)

4. When the air containing pollutants encounters condensed water, it will form sulfuric acid, nitric acid, acetic acid and other substances, causing chemical corrosion. (such as atmosphere containing a lot of sulfide, carbon oxide, nitrogen oxide)