Reasons of Stainless Steel Pipe Rusts

　　Stainless steel pipes resist corrosion because they have a very thin and fine protective film on the surface. It prevents oxygen atoms from continuing to infiltrate and continues to oxidize.Once the film is destroyed, 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 oxides and corroding the metal surface. This type of surface film is subject to destruction in many forms, and is commonly seen in daily life as follows:

　　1. On the surface of stainless steel pipe, deposits of dust or other dissimilar metal particles containing other metal elements accumulate on the surface. In moist air, the condensed water between the deposits and the stainless steel connects the two into a microbattery, which triggers an electrochemical reaction and protects it. The membrane is damaged. This is electrochemical corrosion.

　　2. The surface of stainless steel adheres to organic matter juices (such as vegetables, noodles, soups, etc.). In the presence of water and oxygen, organic acids are formed, and organic acids attack metal surfaces for a long time.

　　3. The surface of the stainless steel adheres to acids, alkalis, and salts (such as alkaline water and lime water splashing on the wall), causing localized corrosion.

　　4. In contaminated air (such as an atmosphere containing a large amount of sulfides, carbon oxides, and nitrogen oxides), condensed water is formed and sulfuric acid, nitric acid, and acetic acid liquids are formed, causing chemical corrosion.