Common Knowledge of Corrosion Protection for Mechanical Seals

Because the special layout and working environment and conditions of mechanical seals are different, the shape of corrosion damage is also varied. The common damage modes of mechanical seals such as tetrafluoro ring and tetrafluoro gasket are corrosion damage, thermal damage and mechanical damage. Corrosion damage is harmful during this period.

Metal ring corrosion

1. Appearance uniform corrosion. If the outer surface of the metal ring touches the corrosive medium, and the metal itself is not corrosion-resistant, it will suffer from external corrosion. Its phenomena are leakage, early wear, damage, vocalization and so on. There are two shapes of uniform corrosion on the surface of metals: film-forming and film-free. Non-film metal corrosion is very risky. It is called stress corrosion cracking. Surfacing carbide and cast iron, tungsten carbide, titanium carbide and other sealing rings are selected to simply present stress corrosion cracking. The corrosion process proceeds at a certain speed, which aggravates the galvanic corrosion.

2. Stress corrosion cracking. Metal in the corrosion and tensile stress together under the effect of assembly mechanical seals, wear resistance. Corrosion of filling F4 ring mainly refers to selective corrosion, dissolution or metamorphosis damage of filling. For example, in hydrofluoric acid, glass fibers molecule hot corrosion, these cracks communicate the entire sealing end face, accelerating the wear of the end face, so as to add leakage.

II. Non-metallic Ring Corrosion

1. Graphite ring corrosion. There are three reasons for the corrosion of impermeable graphite ring impregnated with resin: firstly, when the end surface is overheated and the temperature is higher than 180oC, the impregnated resin will break away from the graphite ring to reduce the wear resistance of the ring; secondly, if impregnated resin is not selected properly, the sealing parts factory of the sealing cooling system should be set up, which is mainly caused by the fault of material selection. The passivation film of film forming corrosion usually has the characteristics of maintenance effect, but the materials used for metal sealing rings, such as stainless steel, cobalt, chromium alloy, etc., are damaged in the end friction. It is difficult to produce new film under anoxic conditions. The corrosion resistant impregnating resin is selected, the high pressure impregnation is selected, and the impregnation depth is 10. It's necessary.

2. Corrosion of polytetrafluoroethylene (tetrafluoroethylene gasket) sealing rings. Chemical changes will occur in the medium, but also reduce the wear resistance; third, impregnation depth of resin is not good, when the impregnation layer is ground, the wear resistance is reduced. F 4 filling, such as glass fibers, first cracks occur in the thin zone, and then develop in depth, cracks occur, sealing ring cracks are usually radial divergent, so one or more can be. Graphite powder, metal powder, etc. to improve its temperature resistance and wear resistance. Corrosion of filling F4 ring mainly refers to selective corrosion, dissolution or metamorphosis damage of filling. For example, in hydrofluoric acid, glass fiber molecule is hot corroded, so what to fill should depend on the specific situation.

3. Oxidation of graphite rings. In oxidizing medium, when the end face is in dry conflict or poor cooling, the temperature of 350-40o C can make the graphite ring react with oxygen, and CO and gas can make the end face rough and even crack. Non-metallic rings also crack under the combined effect of chemical medium and stress.