Why stainless steel is also rust?
When the surface of stainless steel brown rust spots (points), people felt a great sense surprise: that "Stainless steel is not rust, the rust is not stainless steel, and steel may be a problem." In fact, this is a lack of understanding of stainless steel as a one-sided view of the error. Stainless steel in certain conditions will be rusty.
Stainless steel resistant to atmospheric oxidation capacity --- that is, stainless steel, while also have the acid, alkali and salt corrosion medium is the ability to --- that is corrosion resistance. But the size of the corrosion resistance of steel with its own chemical composition, plus in each state, the use of conditions and the environmental media, the type of change. Such as 304 steel, in the dry and clean atmosphere, there is absolutely excellent anti-corrosion capabilities, but will move it to the waterfront area, contains large amounts of salt in the sea mist, will soon rust; and 316 is the performance of steel pipe Good. So it is not any kind of stainless steel and capability in any environment is corrosive, non-rusty.
Stainless steel is by its very thin layer formed on the surface and solid stability of dense chromium-rich oxide film (protective film), to prevent the continued infiltration of oxygen atoms to continue to oxidation, while the accessibility to anti-corrosion ability. Once there is some reason, this film was the constant destruction, air or liquid oxygen atom will continue to infiltrate or metal from the iron atoms in constant evolution out of the formation of porous iron oxide, metal surface corrosion also been continuously . This surface film in the form of destruction of many more common in daily life are the following categories:
First, the stainless steel surface-deposit product with other metal elements containing dust or metal particles heterogeneous attachments, in the humid air, fixtures and stainless steel between the condensate will allow the two together into one micro-cell, triggering the electrochemical response, protective film damage, commonly known that electrochemical corrosion.
Second, the stainless steel surface adhesion of organic juices (such as vegetables, soup, sputum, etc.), in the case of water oxygen to form organic acids, organic acids long while the corrosion of the metal surface.
Third, the stainless steel surface adhesion containing acid, alkali, salts (such as a wall decoration alkaline, lime splash), causing localized corrosion.
Fourth, there is polluted air (eg, contains large amounts of sulfide, carbon dioxide, nitrogen oxides in the atmosphere), case of condensation water to form sulfuric acid, nitric acid, acetic acid solution point, causing chemical corrosion.
