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 concentrations and temperatures on materials varies greatly. For concentrated sulfuric acid with a concentration of more than 80% and a temperature of less than 80 ° C, carbon steel and cast iron have good corrosion resistance, but it is not suitable for high-speed flowing sulfuric acid and is not suitable for pump and valve materials; ordinary stainless steel such as 304 (0Cr18Ni9) and 316 (0Cr18Ni12Mo2Ti) are also of limited use for sulfuric acid media. Therefore, pumps and valves for conveying 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 better sulfuric acid resistance, and fluorine-lined pumps (F46) are a more economical choice.

2. Hydrochloric acid, most metal materials are not resistant to hydrochloric acid corrosion (including various stainless steel materials), and molybdenum-containing ferrosilicon can only be used for hydrochloric acid below 50 ° C and 30%. Contrary to metal materials, most non-metallic materials have good corrosion resistance to hydrochloric acid, so lined rubber pumps and plastic pumps (such as polypropylene, fluoroplastics, etc.) are a good choice for transporting hydrochloric acid.

3. Nitric acid, most metals are rapidly corroded and destroyed in nitric acid. Stainless steel is the most widely used nitric acid-resistant material, and has good corrosion resistance to all concentrations of nitric acid at room temperature. It is worth mentioning that molybdenum-containing stainless steel (such as 316, 316L) The corrosion resistance to nitric acid is not only not better than that of 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, which is one of the most corrosive substances in organic acids. Ordinary steel will be seriously corroded in acetic acid of all concentrations and temperatures. Stainless steel is an excellent acetic acid-resistant material, and 316 stainless steel containing molybdenum can also be used for high temperature and dilute acetic acid steam. For demanding requirements such as high temperature and high concentration acetic acid or 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 ° C and at a concentration of 30%. There are also many factories that still use ordinary steel at 100 ° C and below 75%. Although the corrosion increases, the economy is good. Compared with cast iron, the corrosion resistance of ordinary stainless steel to lye has no obvious advantages. As long as a small amount of iron is allowed to be incorporated in the medium, stainless steel is not recommended. Titanium and titanium alloys or high-alloy stainless steel are mostly used for high-temperature lye.

6. Ammonia (ammonia hydroxide) Most metals and non-metals are slightly corroded in liquid ammonia and ammonia water (ammonia hydroxide), only copper and copper alloys are not suitable for use.

7. Salt water (sea water) The corrosion rate of ordinary steel in sodium chloride solution and sea water and salt water is not too high, and it is generally necessary to use paint protection; all kinds of stainless steel also have a very low uniform corrosion rate, but it may be caused by chloride ions. Localized corrosion, usually 316 stainless steel is better.

8. Alcohols, ketones, esters, ethers, common alcohol media include methanol, ethanol, ethylene glycol, propanol, etc. Ketone media include acetone, butanone, etc. Ester media include various methyl esters, ethyl esters, etc. Ether media include methyl ether, ether, butyl ether, etc. They are basically non-corrosive, and commonly used materials are applicable. Reasonable choices should be made according to the properties of the medium and related requirements. In addition, it is worth noting that ketones, esters, and ethers are soluble to a variety of rubbers, so avoid mistakes when choosing sealing materials.