Stainless steel has the ability to corrode in the medium containing acid, alkali and salt, namely corrosion resistance; It also has the ability to resist atmospheric oxidation, that is, rust; However, the magnitude of its corrosion resistance varies with the chemical composition of the steel itself, the conditions of use and the type of environmental media. Such as 304 stainless steel, in a dry and clean environment has excellent corrosion resistance, but when moved to the seaside area, it will quickly rust in the sea fog containing a lot of salt; 316 material has good performance. So in any environment is not any kind of stainless steel can not rust.
Stainless steel surface formed a layer of extremely thin and strong fine stable chromium oxide film, and then obtain the ability to resist corrosion. Once for some reason, this film is constantly damaged. Oxygen atoms in the air or liquid will continue to penetrate or iron atoms in the metal will continue to separate out, the formation of loose iron oxide, metal surface will be constantly corroded, stainless steel protective film will be destroyed.
Several common cases of stainless steel corrosion in daily life
The surface of stainless steel has accumulated dust, which contains attachments of other metal particles. In the humid air, the condensate water between the attachment and the stainless steel will connect the two into a microbattery, thus triggering an electrochemical reaction, the protective film is destroyed, which is called electrochemical corrosion; The surface of stainless steel adheres to organic juices (such as melons and vegetables, noodle soup, phlegm, etc.), and constitutes organic acids in the case of water and oxygen.
Stainless steel surface will adhere to acid, alkali, salt substances (such as decoration wall alkali, lime water splash), resulting in local corrosion; In polluted air (such as the atmosphere containing large amounts of sulfide, carbon oxide and nitrogen oxide), sulfuric acid, nitric acid and acetic acid will form when met with condensed water, thus causing chemical corrosion.
All the above conditions may damage the protective film on the surface of stainless steel and cause rust. Therefore, in order to ensure that the metal surface is bright and not rusted, we recommend that the stainless steel surface must be cleaned and scrubbed to remove attachments and eliminate external factors. The seaside area should use 316 stainless steel, 316 material can resist seawater corrosion; Some stainless steel pipe chemical composition on the market can not meet the corresponding standards, can not meet the requirements of 304 material, will also cause rust.
Post time: Sep-27-2023
