15961828396
Chinese
Chemical pumps operate in many complex working conditions, and the prominent issue is their corrosion resistance. In the face of various complex working conditions, it is necessary to communicate with the manufacturer in a timely and comprehensive manner when using chemical pumps. For some commonly used chemical media, a brief introduction to the selection of chemical pump materials is provided to facilitate user selection:
1. Sulfuric acid, as one of the highly 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 flow of sulfuric acid and are not suitable as materials for pump valves; Ordinary stainless steels such as 304 (0Cr18Ni9) and 316 (0Cr18Ni12Mo2Ti) are also limited in their use for sulfuric acid media. Therefore, pump valves for transporting sulfuric acid are usually made of high silicon cast iron (with high difficulty in casting and processing) and high alloy stainless steel (alloy 20). 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 at temperatures 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 good choices for transporting hydrochloric acid.
3. Most metals in nitric acid are rapidly corroded and destroyed in nitric acid. Stainless steel is a widely used nitric acid resistant material that 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 better corrosion resistance to nitric acid than ordinary stainless steel (such as 304, 321), but sometimes even worse. For high-temperature nitric acid, titanium and titanium alloy materials are usually used.
4. Acetic acid is one of the highly corrosive substances in organic acids. Ordinary steel will severely corrode in all concentrations and temperatures of acetic acid. Stainless steel is an excellent acetic acid resistant material, and 316 stainless steel containing molybdenum can also be suitable for high temperatures and dilute acetic acid vapors. For demanding requirements such as high temperature and high concentration acetic acid or containing other corrosive media, high alloy stainless steel pumps or fluoroplastic pumps can be selected.
5. Alkali (sodium hydroxide) steel is widely used in sodium hydroxide solutions below 80 ℃ and within 30% concentration. Many factories still use ordinary steel at temperatures below 100 ℃ and 75%. Although corrosion increases, it has good economic efficiency. Compared with cast iron, ordinary stainless steel has no significant advantage in corrosion resistance to alkaline solution. As long as a small amount of iron is allowed to be added to the medium, stainless steel is not recommended. For high-temperature alkaline solution, titanium and titanium alloys or high alloy stainless steel are often used.
6. Ammonia (ammonia hydroxide) Most metals and non-metals have slight corrosion in liquid ammonia and ammonia water (ammonia hydroxide), and only copper and copper alloys are not suitable for use.
7. Salt water (seawater): Ordinary steel has a low corrosion rate in sodium chloride solution, seawater, and salt water, and generally requires coating protection; Various types of stainless steel also have very low uniformity
