1. Sulfuric acid medium is one of the strong corrosive medium. Sulfuric acid is an important industrial raw material with a wide range of uses. Different concentrations and temperatures of sulfuric acid have great differences in the corrosion of materials. For concentrated sulfuric acid carbon steel and cast iron with a concentration of more than 80% and a temperature of less than 80 °C, it has better corrosion resistance, but it is not suitable for high-speed flowing sulfuric acid. It is not suitable for use as a pump The material of the valve is ordinary stainless steel such as 3040Cr18Ni9 and 3160Cr18Ni12Mo2Ti, which also has limited use for sulfuric acid medium. Therefore, the pump valve for conveying sulfuric acid is usually made of high-silicon cast iron and high-alloy stainless steel No. 20 alloy which is difficult to process. Fluoroplastics have better resistance to sulfuric acid. It is a more economical choice to use fluorine-lined pump valve F46. If the pressure is too high and the temperature rises, the point of use of the plastic valve will be impacted, and you can only choose a ceramic ball valve that is much more expensive than it.

2. Hydrochloric acid medium Most metal materials are not resistant to hydrochloric acid corrosion, including various stainless steel materials containing molybdenum and high ferrosilicon, and can only be used for hydrochloric acid below 50 ℃ 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 the best choices for conveying hydrochloric acid. However, if the temperature of such a medium exceeds 150 °C or the pressure is greater than 16 kg, any plastics including polypropylene, fluoroplastics and even PTFE will not be able to do it. At present, there is no ideal valve on the market, but you can try it now. The advantage of the emerging ceramic ball valve is that the self-lubricating torque is small, and the aging life is much longer than that of ordinary valves. Its disadvantage is that the price is much higher than that of plastic valves.

3. Nitric acid medium Most metals are rapidly corroded and destroyed in nitric acid. 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 molybdenum-containing stainless steel such as 316, 316L The corrosion resistance to nitric acid is not only not better than ordinary stainless steel such as 304, 321 and sometimes even worse. For high temperature nitric acid, titanium and titanium alloy materials are usually used.

4. Acetic acid medium It is one of the most corrosive substances in organic acids. Ordinary steel will seriously corrode in acetic acid of all concentrations and temperatures. 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. High-alloy stainless steel or fluoroplastic pumps can be used for harsh requirements such as high-temperature, high-concentration acetic acid or other corrosive media.

5 \5 5. Alkali sodium hydroxide steel is widely used in sodium hydroxide solution below 80 ℃ and 30% concentration, and many petrochemical plants still use ordinary steel at 100 ℃ and below 75%, although the corrosion increases, but 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 mixed into the medium, stainless steel is not recommended. For high-temperature lye, titanium and titanium alloys or high-alloy stainless steel are mostly used.

6. Ammonia Ammonia Hydroxide Most metals and non-metals corrode slightly in liquid ammonia and ammonia water ammonia hydroxide. Only copper and copper alloys should not be used.

7. Chlorine gas and liquid chlorine Most metal valves have limited resistance to chlorine gas corrosion, especially in the case of chlorine gas with water, including various alloy valves. In this case, tetrafluoro valves are a good choice, but chemical plants that produce chlor-alkali will It is found that the tetrafluoro valve takes a little longer and the torque force increases and the problem of tetrafluoro aging will be highlighted, and the leakage that occurs in this case is fatal. It can be considered to replace the original ordinary PTFE-lined valve with PTFE-lined ceramic ball core, and the self-lubricating property of ceramics and the corrosion resistance of PTFE will have a perfect effect.

8. The corrosion rate of ordinary steel in saltwater and seawater is not too high in sodium chloride solution, seawater and saltwater. Generally, coatings must be used to protect various types of stainless steel. There is also a very low uniform corrosion rate, but local corrosion may be caused by chloride ions. Usually, 316 stainless steel is used. better.

9. Alcohols, ketones, esters, ethers. Common alcohol media include methanol, ethanol, ethylene glycol, propanol and other ketone media, including acetone, butanone and other ester media. There are various methyl esters, ethyl acetates, etc. Ester and other ether media include methyl ether, ethyl ether, butyl ether, etc. They are basically non-corrosive and commonly used materials are suitable for specific selection. Reasonable selection should also be made according to the properties of the medium and related requirements. It is also worth noting that ketones, esters, and ethers are soluble in various rubbers to avoid mistakes when choosing sealing materials.