Valve corrosion refers to the phenomenon that the valve material is damaged by chemical, electrochemical, mechanical or thermal action under a specific working environment. Corrosion is one of the important factors of valve damage. Therefore, in valve protection, valve corrosion protection is an important consideration. In order to combat valve corrosion, the following methods can be taken:
1, the selection of corrosion resistant materials: the use of good corrosion resistance materials to manufacture valves, such as stainless steel, alloy steel, etc. Select the appropriate material according to the characteristics of the working environment to prevent valve damage caused by corrosion.
2, the use of non-metallic materials: non-metallic corrosion resistance is good as long as the valve temperature and pressure meet the requirements of non-metallic materials, not only can solve the corrosion problem, but also save precious metals. Valve body, valve cover, bushing, sealing surface and other commonly used non-metallic materials. As for gaskets, gaskets are mainly made of non-metallic materials. The use of polytetrafluoroethylene, chlorinated polyether and other plastics, as well as natural rubber, neoprene rubber, nitrile rubber and other rubber. As the valve liner, the valve body and valve cover body are made of ordinary cast iron and carbon steel. It not only ensures the strength of the valve, but also ensures that the valve is not corroded.
3, surface coating: the surface of the valve is coated to form a protective layer with good corrosion resistance (600/1) to reduce the corrosion effect on the valve. Common coating materials include paint, epoxy resin coating, polyurea coating, plating and so on.
4, Valve stem anticorrosive: widely used nitriding, boronizing, chromium plating, nickel plating and other surface treatment processes to improve its corrosion resistance (Valve Guardian) and wear resistance. Different surface treatments should be suitable for different stem materials and working environments. For bars in contact with the atmosphere and water vapor media and filled with asbestos, hard chromium plating and gas nitriding process can be used (ion nitriding process is not applicable to stainless steel); The valve in hydrogen sulfide atmosphere is coated with galvanized high-phosphorus nickel, which has better protection performance. 38CrMoAlA uses ion and gas nitriding to resist corrosion, but is not suitable for hard chromium plating; 2Cr13 can resist ammonia corrosion after cooling gas nitrided carbon steel is also resistant to ammonia corrosion, all phosphorus and nickel coatings are not resistant to ammonia corrosion; 38CrMoAlA material has excellent corrosion resistance and comprehensive properties after gas nitriding, and is used to make valve stems.
5, anti-corrosion treatment: anti-corrosion treatment of the valve, such as sandblasting, shot blasting, etc., to remove the surface oxidation layer and pollutants, increase the corrosion resistance of the valve.
6, regular maintenance: regular valve overhaul, cleaning and maintenance, timely discovery and treatment of corrosion on the valve, in order to extend the service life of the valve.
7, the control of corrosion environment: the so-called environment has two broad and narrow. Broadly speaking, it refers to the environment around the valve installation site and the medium flowing within it; Narrow sense refers to the conditions around the valve installation site. Most environments cannot be controlled and production processes cannot be changed at will. Only in the case of no damage to the product, process, etc., can it be used to control the environment, such as boiler water deoxidation, oil refining process, and pH value adjustment alkali. The atmosphere is full of dust, water vapor and smoke, especially in the production environment, such as the smoke emitted by the equipment, halogen, toxic gases and dust, etc., will cause different degrees of corrosion to the valve.
In short, the way to combat valve corrosion mainly includes material selection, surface coating, anti-corrosion treatment, regular maintenance and control of the corrosion environment. Taking different measures according to the specific situation can effectively reduce the corrosion damage of the valve. (2024-03-14)
