Chemical valve material selection

For a long time, corrosion is one of the most troublesome hazards of chemical equipment, ranging from damage to equipment, causing accidents and even catastrophe. According to statistics, about 60% of the destruction of chemical equipment is caused by corrosion, so the selection of chemical valves must first pay attention to the scientific material selection. The following for some common chemical media to talk about the selection of the main points: 1. Sulfuric acid as a strong corrosive medium, sulfuric acid is a very broad use of important industrial raw materials. Different concentrations and temperatures of sulfuric acid on the corrosion of materials vary greatly, for the concentration of more than 80%, the temperature is less than 80 ℃ of concentrated sulfuric acid, carbon steel and cast iron has good corrosion resistance, but it is not suitable for high-speed flow of sulfuric acid, Not suitable for pump valve material; ordinary stainless steel, such as 304 (0Cr18Ni9), 316 (0Cr18Ni12Mo2Ti) sulfuric acid medium is also limited use. Therefore, the delivery of sulfuric acid pump valve usually adopts high silicon cast iron (casting and processing difficult), high alloy stainless steel (20 alloy) manufacturing. Fluorine plastic has better resistance to sulfuric acid, fluorine-lined valve is a more economical choice. 2. Acetic acid It is one of the most corrosive substances in organic acids. Ordinary steel will be seriously corroded in all concentrations and temperatures of acetic acid. Stainless steel is an excellent acetic acid-resistant material. Molybdenum-containing 316 stainless steel is also suitable for high temperature and Dilute acetic acid steam. For high temperature and high concentration of acetic acid or other corrosive media and other harsh requirements, the choice of high-alloy stainless steel valve or fluorine plastic valve. 3. Hydrochloric acid solution Most of the metal materials are not resistant to hydrochloric acid corrosion (including a variety of stainless steel), molybdenum high ferrosilicon can only be used for 50 ℃, hydrochloric acid below 30%. In contrast to metallic materials, the vast majority of non-metallic materials have good corrosion resistance to hydrochloric acid, so lined rubber valves and plastic valves (such as polypropylene, fluoroplastic, etc.) are the best choice for the delivery of hydrochloric acid. 4. Nitric acid Most metals are mostly corrosive nitric acid corrosion damage, stainless steel is the most widely used nitric acid-resistant materials, all concentrations of nitric acid at room temperature have good corrosion resistance, it is worth mentioning that the molybdenum-containing stainless steel (such as 316,316 L) corrosion resistance to nitric acid is not only not superior to ordinary stainless steel (such as 304,321), and sometimes even worse. For high temperature nitric acid, usually titanium and titanium alloy materials.

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