Stainless steel is not perfect and does not rust, but its oxidation resistance is stronger than ordinary steel, so it is called stainless steel. Stainless steel BL flange not only has the ability to resist atmospheric oxidation, but also has the ability to corrode in the medium containing acid, alkali and salt. However, the size of its anti-corrosion ability varies with the chemical composition of the steel itself, the interaction state, the operating conditions and the type of environmental media.

　　BL flange stainless steel is based on the extremely thin, solid, dense and stable chromium-rich oxide film (protection film) formed on its surface, which prevents the penetration and oxidation of oxygen atoms and continues to obtain rust resistance. Once there is such a reason, the membrane will be destroyed from time to time.

　　The oxygen atoms in the air or liquid of the stainless steel BL flange will penetrate from time to time, and the iron atoms in the metal will be separated from time to time to form scattered iron oxides, and the metal surface will rust from time to time. There are many ways to damage this surface film, and the following are common in daily life: The surface of stainless steel contains dust or other metal particles containing other metal elements. In the humid air, the stainless steel BL flange adheres to the condensed water between the two, connecting the two into a miniature battery, causing an electrochemical reaction, and the protective film is damaged, which is called electrochemical corrosion.

　　In the presence of water and oxygen, the stainless steel BL flange will form an organic acid, which will stop the corrosion of the metal surface for a long time. The surface of stainless steel BL flange contains acid, alkali, salt and other substances, which constitute local corrosion. In polluted air, condensed water will form spots of sulfuric acid, nitric acid and acetic acid, causing chemical corrosion.