Material selection method for chemical pumps

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 materials varies greatly with different concentrations and temperatures of sulfuric acid. For concentrated sulfuric acid with concentrations above 80% and temperatures below 80 ℃, carbon steel and cast iron have good corrosion resistance, but they are not suitable for high-speed flowing sulfuric acid and are not suitable as materials for pumps and valves; Ordinary stainless steels such as 304 (0Cr18Ni9) and 316 (0Cr18Ni12Mo2Ti) also have limited applications in sulfuric acid media. Therefore, pumps and valves for transporting sulfuric acid are usually made of high silicon cast iron (difficult to cast and process) and high alloy stainless steel (No. 20 alloy). Fluoroplastics have good sulfuric acid resistance, and using a fluorine lined pump (F46) is a more economical choice.
2. Most metal materials, including various stainless steel materials, are not resistant to hydrochloric acid corrosion. Molybdenum containing high silicon iron can only be used for hydrochloric acid below 50 ℃ and 30%. Contrary to metal materials, the vast majority of non-metallic materials have good corrosion resistance to hydrochloric acid, so lined rubber pumps and plastic pumps (such as polypropylene, fluoroplastics, etc.) are the best choices for transporting hydrochloric acid.
3. Most metals in nitric acid are rapidly corroded and destroyed in nitric acid, and stainless steel is the most widely used nitric acid resistant material. It has good corrosion resistance to all concentrations of nitric acid at room temperature. It is worth mentioning that stainless steel containing molybdenum (such as 316, 316L) not only has inferior corrosion resistance to nitric acid compared to ordinary stainless steel (such as 304, 321), but sometimes even worse. For high-temperature nitric acid, titanium and titanium alloy materials are usually used.