To prevent corrosion, you must first understand why the mechanical seal is corroded

Mechanical seal is a shaft sealing device used for rotating fluid machinery. Reliable screw pump with small leakage, long service life and low power consumption. No need for frequent repairs, and can adapt to the automation of the production process and high temperature, low temperature, high pressure, vacuum, high speed and various strong corrosive media. If it is not properly protected, the mechanical seal will still be corroded. If you want to know the method of anti-corrosion, you must first understand the principle of corrosion. 1. Corrosion of the metal ring 1. The surface is uniformly corroded. If the surface of the metal ring is in contact with the corrosive medium, and the metal itself is not resistant to corrosion, surface corrosion will occur, and the phenomena are leakage, early wear, damage, and sound. The uniform corrosion of the metal surface has two forms: film-forming and film-free. The metal without film is very dangerous to corrode, which is called stress corrosion cracking. The use of surfacing cemented carbide and sealing rings such as cast iron, tungsten carbide, and titanium carbide can easily show stress corrosion. Split. The corrosion process proceeds at a certain speed, which intensifies the galvanic corrosion. 2. Stress corrosion cracking. Metal cartridge mechanical seal under the combined action of corrosion and tensile stress, wear resistance. The corrosion of the filled F4 ring mainly refers to the selective corrosion, dissolution or decay of the filling. The glass fiber molecules are thermally corroded, and these cracks communicate with the entire sealing end face, which accelerates the wear of the end face and increases the leakage. Second, non-metallic ring corrosion 1. Graphite ring corrosion. The impermeable graphite ring impregnated with resin has three reasons for its corrosion: one is that when the end face is overheated and the temperature is greater than 180oC, the impregnated resin must be broken off the graphite ring, so that the wear resistance of the ring is reduced; Improper selection, so the establishment of a sealing parts factory for the sealing cooling system is mainly caused by the wrong selection of materials. In film-forming corrosion, the passivation film generally has the characteristics of protection, but the materials used for metal sealing rings, such as stainless steel, cobalt, chromium alloy, etc., the passivation film on the surface is damaged in the end face friction The film is difficult to form. It is very necessary to choose a corrosion-resistant impregnating resin and high-pressure impregnation to increase the impregnation depth. 2. Corrosion of PTFE (tetrafluoroethylene gasket) sealing ring. There will be chemical changes in the medium, which will also reduce the wear resistance. Third, the depth of resin impregnation is not enough. When the impregnated layer is removed, the wear resistance will decrease. Filled with F4 such as glass fiber, cracks first occur in the thin area, and then develop to the depth and split. The cracks of the sealing ring are generally radially divergent, and there may be one or more cracks. Graphite powder, metal powder, etc. to improve its temperature resistance and wear resistance. The corrosion of the filled F4 ring mainly refers to the selective corrosion, dissolution or decay of the filling. Glass fiber molecules are hot corroded, so what to fill should be determined according to the specific situation. 3. Oxidation of graphite rings. In an oxidizing medium, when the end face is in dry contact or poor cooling, the temperature of 350-40°C can cause the graphite ring to react with oxygen, generate CO, gas, and make the end face rough and even split. Non-metallic rings will also split under the combined action of chemical media and stress.