Why does stainless steel rust? When a brown rust (spot) appears on the surface of a stainless steel tube, people are surprised: "The stainless steel does not rust, rust is not stainless steel, and there may be a problem with the steel." In fact, this is a one-sided misconception about the lack of understanding of stainless steel. Stainless steel will rust under certain conditions. Stainless steel has the ability to resist atmospheric oxidation - that is, stainless, but also has the ability to resist corrosion in media containing acid, alkali, and salt - ie corrosion resistance. However, the corrosion resistance of the steel varies with the chemical composition of the steel itself, the interaction state, the conditions of use, and the type of environmental media. Such as 304 steel pipe, in the dry clean atmosphere, there is absolutely excellent resistance to corrosion, but it will be moved to the sea area, in the sea fog containing a lot of salt, will quickly rust; and 316 steel performance good. Therefore, not any kind of stainless steel can resist corrosion and rust in any environment.