The cause of stainless steel rust and processing method

Why is stainless steel rust? When the stainless steel tube surface appear brown rusty spot ( Point) , big surprised: people think 'stainless steel is not rusty, rust is not stainless steel, is likely to be the problem of steel'. Actually, this is a one-sided error for a lack of understanding of stainless steel. Stainless steel under certain conditions will be rusty. Stainless steel has the ability of resistance to atmospheric oxidation - - - Namely, stainless, also has in the medium containing acid, alkali, salt is the ability of corrosion - - - The corrosion resistance. But the size of its ability to resist corrosion was with the chemical composition of steel itself, and each state, using conditions and environmental medium type and change. As 304 steel tube, in dry, clean atmosphere, have absolute good corrosion resistance, but it will be moved to the coastal areas, in contains a great deal of sea salt fog, will soon be rusty; And 316 steel tube is good. So, not any kind of stainless steel, in any environment corrosion, no rust. Stainless steel is formed on the surface of a layer of a very thin and fine and stable solid rich chromium oxide film ( Protective film) To prevent the oxidation of oxygen infiltration, continue, and ability to resist corrosion. Once you have some reason, this film has been continuously destroyed, air or liquid oxygen in the original child will constantly infiltration or metallic iron atom separation out unceasingly, forming loose iron oxide, metal surface are also constantly rust. The surface membrane damage in the form of many, see more of in daily living has the following several kinds: 1. Deposited on the surface of the stainless steel contain other metal elements of attachments, or heterogeneous metal particles of dust in the humid air, attachments and stainless steel, the condensed water between the both together as a micro battery, triggers the electrochemical reaction, protective film is damaged, to call the electrochemical corrosion. 2. Stainless steel surface adhesion organic juice ( Such as vegetables, noodle soup, sputum, etc. ) , under the condition of water is oxygen, organic acid, organic acid to for a long time and are on the surface of the metal corrosion. 3. Stainless steel surface adhesion containing acid, alkali, salt substances ( Like to decorate the walls of caustic soda, stone splash water) , cause local corrosion. 4. Where there is pollution in the air ( Such as contains a lot of sulfur, oxidation of carbon, nitrogen oxide atmosphere) , encounter condensed water to form sulfuric acid, nitric acid, acetic acid, liquid, chemical corrosion. The above situation can be caused by the destruction of the stainless steel surface protective film cause corrosion. So, in order to ensure the surface of the permanent bright metal, not rust, we suggest that: 1. Decorative stainless steel surfaces must often swabbed clean, remove attachments, eliminate the cause of external factors. 2. 316 coastal areas to use 316 stainless steel material, material corrosion resistance to sea water. 3. Some chemicals stainless steel tube can not be on the market accords with relevant national standards, amounted to less than 304 material requirements. So can also cause rust, which requires users to choose reputable manufacturer product carefully.