Stainless steel has the ability to resist atmospheric oxidation, that is, stainless, but also with acid, Alkali, the salt medium is the ability to corrosion, that is, corrosion resistance. However, the corrosion resistance of the steel varies with the chemical composition of the steel itself, the state of addition, the use conditions and the type of environmental media. Stainless Steel 304, for example, has excellent resistance to rust in a dry, clean atmosphere, but moves it to a coastal area where it quickly rusts in a sea fog that contains a lot of salt, while the 316 performs well. Therefore, not any kind of stainless steel, in any environment can be corrosion-resistant, non-rusty.
Stainless steel depends on its surface to form a very thin and strong thin thin stable chromium-rich oxide film (protective film) , to prevent oxygen atoms from further infiltration, further oxidation, and obtain the ability of corrosion resistance. Once the film is damaged for some reason, the oxygen atoms in the air or liquid will penetrate into it or the iron atoms in the metal will be separated out to form loose iron oxide and the surface of the metal will be corroded continuously.
This kind of surface film is destroyed in many ways, the following are common in daily life:
1. The surface of stainless steel is covered with dust containing other metal elements or the adhesion of dissimilar metal particles. In the humid air, the condensation water between the adhesion and stainless steel connects the two into a micro-battery, which initiates an electrochemical reaction The damage to the protective film is called electrochemical corrosion.
2. Stainless steel surface adhesion of organic juice (such as vegetables, noodle soup, etc.) , in the presence of water and oxygen, the formation of organic acids, long-term organic acids on the metal surface corrosion.
3. Stainless steel surface adhesion containing acid, Alkali, salt substances (such as decoration walls of alkaline water, lime water splashing) , causing local corrosion.
4. In the polluted air (such as the air containing a lot of Sulfides, carbon monoxide, nitrogen oxide) , the condensation water, the formation of sulfuric acid, nitric acid, acetic acid points, causing chemical corrosion.
Above all can cause the stainless steel surface protective film damage caused by corrosion. So, to ensure that the surface of the metal is permanently bright and free from rust, we have the following Two Suggestions:
1. Stainless steel surfaces must be cleaned and scrubbed from time to time to remove attachments and external factors that cause the modification.
2. If the use of the environment is in the seaside, then it is recommended to use 316 material. Because the 316 material is resistant to seawater.
Post time: Jul-28-2021