Reasons Why Stainless Steel Rusts

Stainless steel has the ability to resist atmospheric oxidation—that is, stainless steel, and also has the ability to resist corrosion in media containing acids, alkali, and salt—that is, corrosion resistance. However, its corrosion resistance changes with the chemical composition of the steel itself, its additive state, usage conditions and environmental medium types. Like 304 steel pipes, in the atmosphere of dry cleansing, absolute good resistant to tarnishing ability is arranged. But if it is moved to riviera, in containing the sea fog of a large amount of salts, will soon get rusty; 316 steel pipes show excellent corrosion resistance. good. Therefore, not any kind of stainless steel can resist corrosion and rust in any environment.

Stainless steel relies on the formation of an extremely thin, strong, fine, and stable chromium-rich oxide film (protective film) on its surface to prevent the continued penetration and oxidation of oxygen atoms, thereby obtaining the ability to resist rust. Once this film is continuously damaged for some reason, oxygen atoms in the air or liquid will continue to penetrate or iron atoms in the metal will continue to separate out, forming loose iron oxide, and the metal surface will be continuously corroded. There are many forms of damage to this surface film, and the most common ones in daily life are as follows:

       1. Dust containing other metal elements or attachments of heterogeneous metal particles accumulate on the surface of stainless steel. In humid air, the condensed water between the attachments and stainless steel connects the two into a micro-battery, triggering an electrochemical reaction. , the protective film is damaged, which is called electrochemical corrosion.

       2. Organic juice (such as vegetables, noodle soup, etc.) adheres to the surface of stainless steel. In the presence of water and oxygen, it forms organic acid. For a long time, the organic acid corrodes the metal surface.

       3. The surface of stainless steel contains acids, alkalis, and salts (such as alkaline water and lime water splashed on walls), causing local corrosion.

       4. In polluted air (such as an atmosphere containing a large amount of sulfides, carbon oxides, and nitrogen oxides), when encountering condensed water, sulfuric acid, nitric acid, and acetic acid liquid points will form, causing chemical corrosion.