Stainless steel is not easy to rust, but it can also rust. The reason why stainless steel is not easy to rust has a lot to do with the composition of stainless steel. In addition to iron, stainless steel also contains chromium, nickel, aluminum, silicon, etc. The chromium content of general stainless steel is generally not less than 12%, and the highest is even 18%. After adding chromium and other elements to steel, the properties of steel can be changed. For example, the molecular structure of steel is more uniform, and it is easier to form a dense oxide protective film on the surface of steel, thereby greatly improving the corrosion resistance of stainless steel. Therefore, stainless steel can resist corrosion from fire, water, acid, alkali and various solutions, and will not rust. Scientists have found that the more uniform the internal structure of steel, the more closely the various components are connected, and the more difficult it is for corrosive substances to invade. In addition, a layer of oxide protective film is attached to the surface, just like putting armor on steel, so it is naturally not easy to rust.
Why does stainless steel also rust? When brown rust spots (dots) appear on the surface of stainless steel pipes, people are surprised: they think "stainless steel does not rust, and if it rusts, it is not stainless steel, and there may be something wrong with the steel." In fact, this is a one-sided and wrong view of stainless steel that lacks understanding. Stainless steel will also rust under certain conditions. Stainless steel has the ability to resist atmospheric oxidation, that is, stainlessness, and also has the ability to resist corrosion in media containing acids, alkalis, and salts, that is, corrosion resistance. However, the magnitude of its corrosion resistance varies with the chemical composition of the steel itself, the state of addition, the conditions of use, and the type of environmental media. For example, 304 steel pipes have absolutely excellent corrosion resistance in dry and clean atmosphere, but if they are moved to coastal areas, they will soon rust in sea fog containing a lot of salt; while 316 steel pipes perform well. Therefore, not all kinds of stainless steel can resist corrosion and not rust in any environment.