Material selection method of chemical pump

For a long time, corrosion is one of the most headaches of chemical equipment. If it is a little careless, the device is damaged lightly, and the accident causes the accident and even causes disasters. According to relevant statistics, about 60%of the destruction of chemical equipment is caused by corrosion. Therefore, when the chemical pump selection is selected, the scientificity of the selection of materials should be paid first. There is usually a misunderstanding that stainless steel is a “universal material”. It is very dangerous regardless of the medium and environmental conditions. This is very dangerous. Let’s talk about the main points of the selection of chemical pumps for some commonly used chemical media:
1. As one of the strong corrosive media, sulfuric acid is an important industrial raw material with a wide range of uses. Sulfuric acid with different concentrations and temperatures has a large difference in corrosion of materials. For concentrations with concentrations of more than 80%or more than 80 ° C, carbon steel and cast iron have good corrosion resistance, but it is not suitable for high -speed flowing sulfuric acid. It is not applicable to the material of the pump valve; ordinary stainless steel such as 304 (0CR18NI9) and 316 (0CR18NI12MO2TI) are also limited to sulfuric acid medium. Therefore, the pump valve that transports sulfuric acid is usually manufactured with high silicon cast iron (casting and processing difficulty) and high alloy stainless steel (alloy 20). Fluor plastic has good sulfur resistance, and the use of fluorine pump (F46) is a more economical choice.
2. Most metal materials are not resistant to hydrochloric acid corrosion (including various stainless steel materials), and molybdenum high -silicon iron can also be used only for 50 ° C and 30%of hydrochloric acid. Contrary to metal materials, most non -metallic materials have good corrosion resistance to hydrochloric acid. Therefore, inner lining rubber pumps and plastic pumps (such as polypropylene, fluoroplastics, etc.) are the best choices for transporting hydrochloric acid.
3. Most nitric acid metals are mostly corroded and destroyed in nitric acid. Stainless steel is the most widely used nitrogen -resistant material. It has good corrosion resistance to all concentrations of all concentrations at room temperature. 316, 316L) The corrosion resistance of nitric acid is 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 is one of the most corrosive substances in organic acids. Ordinary steel will be severely corroded in all concentrations and temperatures. Stainless steel is an excellent acetic acid -resistant material. 316 stainless steel containing molybdenum can also be suitable for high temperature and high temperature and. Steam acid steam. When high temperature and high -concentrated 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 solution below 80 ° C and 30%concentration. There are also many factories still use ordinary steel when 100 ° C and 75%. Essence The corrosion resistance of ordinary stainless steel to alkali solution has no obvious advantages compared with the cast iron. As long as the medium is allowed to include a small amount of iron, it is not recommended to use stainless steel. For high temperature alkali, titanium and titanium alloy or high alloy stainless steel are mostly used.
6. Most of the ammonia (ammonia oxide) most of the metal and non -metallic corrosion in liquid ammonia and ammonia (ammonia) are mild, and only copper and copper alloy should not be used.
7, saltwater (seawater) ordinary steel in sodium chloride solution, seawater and salt water is not too high, and generally must be protected by coatings; various types of stainless steel also have a very low uniform corrosion rate, but it may cause locality due to chloride ions. Corrosion is usually better using 316 stainless steel.
8. Alcohol, ketone, ester, and ether commonly have methanol, ethanol, ethylene glycol, propylene, and other ketones. Ethyps, etc., ether media include methyl ether, ether, butyl ether, etc. They basically have no corrosiveness, and commonly used materials can be applicable. When the specific selection, it should also make reasonable choices according to the attributes of the medium and related requirements. It is also worth noting that ketone, ester, and ether are dissolved in a variety of rubber and avoid errors when selecting sealing materials.