Why does stainless steel pipe fittings rust too? Why does stainless steel also rust? When the surface of stainless steel pipe fittings appear brown rust spots (points), people are surprised: that "stainless steel is not rust, rust is not stainless steel, it may be a problem with the quality of steel". In fact, this is a one-sided misconception of the lack of understanding of stainless steel. Stainless steel

Stainless steel has the ability to resist atmospheric oxidation - that is, stainless, but also in the medium containing acid, alkali, salt is the ability to corrode - that is, corrosion resistance. But the size of its corrosion resistance is with its steel itself chemical composition, plus mutual state, the use of conditions and environmental media type and change. Such as 304 steel pipe, in a dry and clean atmosphere, there is absolutely excellent corrosion resistance, but it will be moved to the seaside area, in the sea spray containing a large amount of salt, will soon rust; and 316 steel pipe is good performance. Therefore, not any kind of stainless steel, in any environment can be resistant to corrosion, not rust.  Stainless steel is formed on its surface by a layer of very thin and strong and dense stable chromium-rich oxide film (protective film) to prevent the continued penetration of oxygen atoms, continue to oxidation, and the ability to resist rust and corrosion. Once there is some reason, this film is constantly destroyed, the oxygen atoms in the air or liquid will continue to infiltrate or metal iron atoms constantly precipitated out, the formation of loose iron oxide, the metal surface is also subject to constant rusting. This surface film is damaged in many forms.