Is stainless steel really stainless?

 Is stainless steel really stainless?

Stainless steel (Stainless Steel) is resistant to air, steam, water and other weakly corrosive media or stainless steel. Its corrosion resistance depends on the alloy elements contained in the steel. Generally, the chromium content is greater than 12% and it has Corrosive steel is called stainless steel. Chromium is the basic element for obtaining corrosion resistance of stainless steel. When the chromium content in steel reaches about 12%, chromium reacts with oxygen in the corrosive medium to form a thin oxide film (passivation film) on the surface of the steel. ) To prevent further corrosion of the steel substrate. When the oxide film is continuously damaged, the oxygen atoms in the air or liquid will continue to infiltrate or the iron atoms in the metal will continue to separate out, forming loose iron oxide, and the stainless steel surface will be continuously rusted.
The size of stainless steel’s anti-corrosion ability changes with the chemical composition of the steel itself, the state of protection, the conditions of use, and the type of environmental medium. For example, 304 steel pipe has absolutely excellent rust resistance in a dry and clean atmosphere, but it will be rusted quickly when it is moved to the seashore area in sea fog containing a large amount of salt. good. Therefore, it is not any kind of stainless steel, which can be resistant to corrosion and rust under any environment.