Why stainless steel will rust when the surface of the stainless steel tube brown rust ( points ) , people great surprise : that " Stainless steel is not rusty , rusty steel is not , may be a problem with the steel ." In fact , this is a lack of understanding of a one-sided stainless misconception . Under certain conditions, stainless steel will rust in .
Stainless steel has the ability to resist the atmospheric oxidation --- ie stainless steel , while also having acid , alkali and salt corrosion medium is the ability --- namely corrosion resistance. But the size of its corrosion resistance of the steel itself is with its chemical composition, plus inter- state media types and environmental conditions changed . Such as 304 steel , in a clean dry atmosphere is absolutely excellent anti -corrosion ability , but to move it to the waterfront area , contains a lot of salt in the sea of fog , will soon rust ; while 316 steel is manifested good . Therefore , not any kind of stainless steel , in any environment resistant to the corrosive , does not rust .
Stainless steel is extremely thin and sturdy fine stable chromium-rich oxide film ( protective film ) formed on the surface , to prevent further infiltration of oxygen atoms, to oxidation , and ability to obtain anti- corrosion . Once there is some reason , this film was constantly undermined , air or liquid oxygen atoms will continue to infiltrate or metal from iron atoms constantly analyze , forming loose iron oxide, metal surface corrosion will continue to suffer . This takes many forms surface film damaged , daily life is more common are the following :
A, stainless steel surface with attachments containing the accumulated dust or other metallic elements heterogeneous metal particles in the humid air , condensate and stainless steel fixtures between the two together into a micro- battery , causing the electrochemical reaction , the protective film is damaged, call it that electrochemical corrosion.
B, stainless steel surface adhesion of organic juice ( such as vegetables , soup , sputum , etc. ) , in the case of water oxygen to form organic acids, organic acid corrosion of time the metal surface .
C, stainless steel surface adhesion containing acids, bases, salts ( such as wall decoration alkaline , lime splash ) , causing localized corrosion.
D, in air pollution (e.g., containing sulfides, carbon dioxide , nitrous oxide atmosphere ) , the case of the condensation water to form sulfuric acid, nitric acid, acetic acid solution points cause chemical corrosion.