When brown rust spots (spots) appear on the surface of stainless steel plate, people are greatly surprised: they think that "stainless steel does not rust, and rust is not stainless steel, but may be a problem with steel". In fact, this is a one-sided wrong view that lacks understanding of stainless steel. Stainless steel rusts under certain conditions. Stainless steel not only has the ability to resist atmospheric oxidation, that is, rust prevention, but also has the ability to corrode in the medium containing acid, alkali and salt, that is, corrosion resistance. However, its corrosion resistance varies with the chemical composition of its steel, the state of mutual reinforcement, the use conditions and the types of environmental media. For example, 304 steel pipe has absolutely excellent anticorrosion ability in dry and clean atmosphere, but in sea fog with high salt content, if it is moved to coastal areas, it will soon rust; 3 16 steel pipe performed well. Therefore, not all stainless steel plates can resist corrosion and rust in any environment. Stainless steel forms a very thin, firm and stable chromium-rich oxide film (protective film) on its surface, which prevents oxygen atoms from continuing to infiltrate and oxidize and gains corrosion resistance. Once this film is destroyed for some reason, oxygen atoms in air or liquid will continue to penetrate or iron atoms in metal will continue to separate to form loose iron oxide, and the metal surface will continue to be corroded. There are many forms of damage to this surface film, and the following are common in daily life: 1. Dust containing other metal elements or attachments of different metal particles are deposited on the surface of stainless steel. In humid air, the condensed water between accessories and stainless steel connects them into a miniature battery, which causes electrochemical reaction and the protective film is destroyed. This is called electrochemical corrosion. 2. Organic fruit juice (such as melons, vegetables, noodle soup, phlegm, etc.). ) attached to the surface of stainless steel, organic acids will be formed in the presence of water and oxygen, which will corrode the metal surface for a long time. 3. Substances containing acid, alkali and salt are adhered to the surface of stainless steel (such as alkali water and lime water splashing for wall decoration), causing local corrosion. 4. In polluted air (such as air containing a lot of sulfides, carbon oxides and nitrogen oxides), condensed water will form sulfuric acid, nitric acid and acetic acid, causing chemical corrosion. All the above conditions will lead to the damage of the protective film on the stainless steel surface, leading to corrosion. Therefore, in order to ensure that the metal surface is permanently bright and not corroded, Ai suggested: 1. The chemical composition of some stainless steel plates in the market can not meet the corresponding national standards and the material requirements of 304. So it will also cause rust, which requires users to carefully choose products from reputable manufacturers. Pipeline construction and construction precautions In order to prevent scratches and pollutants from adhering during construction, stainless steel construction is carried out in the state of film pasting. However, with the extension of time, according to the service life of the film, the surface should be cleaned and special stainless steel tools should be used when the film is removed after construction. When cleaning common tools with general steel, clean them to prevent iron chips from sticking. Care should be taken not to let highly corrosive magnetic and stone luxury cleaning drugs contact the stainless steel surface. If it comes into contact, it should be cleaned immediately. After the construction, use neutral detergent and water to wash the cement, powder and ash attached to the surface. 2. Decorative stainless steel surfaces must be cleaned and scrubbed frequently to remove attachments and external factors causing decoration. 3. 3 16 stainless steel should be used in coastal areas, which can resist seawater corrosion.