According to relevant statistics, about 60% of the damage of chemical pumps is caused by corrosion. Therefore, when selecting chemical process pumps, we should first pay attention to the scientificity of material selection. There is usually a misunderstanding that stainless steel is a "universal material". It is very dangerous to hold a stainless steel pump regardless of medium and environmental conditions. 1) Sulfuric acid, as one of the strong corrosive media, is an important industrial raw material with a wide range of uses. The corrosion of sulfuric acid with different concentration and temperature is quite different. For concentrated sulfuric acid with concentration above 80% and temperature less than 80 ℃, carbon steel and cast iron have good corrosion resistance, but it is not suitable for high-speed flow sulfuric acid chemical process pump and is not suitable for chemical process pump materials; Ordinary stainless steels such as 304 (0Cr18Ni9) and 316 (0Cr18Ni12Mo2Ti) are also limited to sulfuric acid medium. Therefore, the chemical process pump conveying sulfuric acid is usually made of high silicon cast iron (difficult to cast and process) and high alloy stainless steel (No. 20 alloy). Fluoroplastics have good resistance to sulfuric acid. It is a more economical choice to use fluorine lined chemical process pump (F46). 2) Hydrochloric acid most metal materials are not resistant to hydrochloric acid corrosion (including various stainless steel materials), and molybdenum containing high silicon iron can only be used for hydrochloric acid below 50 ℃ and 30%. In contrast to metal materials, most non-metallic materials have good corrosion resistance to hydrochloric acid, so lined rubber pumps and plastic chemical process pumps (such as polypropylene, fluoroplastics, etc.) are the best choices for transporting hydrochloric acid. 3) Most general metals of nitric acid are rapidly corroded and damaged in nitric acid. Stainless steel is the most widely used material for nitric acid resistant chemical process pump. It has good corrosion resistance to all concentrations of nitric acid at room temperature. It is worth mentioning that the corrosion resistance of molybdenum containing stainless steel (such as 316 and 316L) to nitric acid is not only better than that of ordinary stainless steel (such as 304 and 321), but sometimes even worse. For high temperature nitric acid chemical process pump, titanium and titanium alloy materials are usually used. 4) Acetic acid is one of the most corrosive substances in organic acids. Ordinary steel will be seriously corroded in acetic acid at all concentrations and temperatures. Stainless steel is an excellent acetic acid resistant chemical process pump material. 316 stainless steel containing molybdenum can also be used for high temperature and dilute acetic acid steam. For high temperature and high concentration acetic acid or containing other corrosive media and other harsh requirements, high alloy stainless steel chemical process pump or chemical process pump made of fluoroplastic can be selected.
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