Industry dynamic

Industry dynamic

2018-04-12 10:06:22

Chemical pump delivery of acid and alkali how to determine the material

1, sulfuric acid as one of the strong corrosive medium, sulfuric acid is a very wide range of important industrial raw materials. Corrosion of different concentration and temperature of sulfuric acid on the material difference is bigger, the concentration is above 80%, the temperature is less than 80 ℃ concentrated sulfuric acid, carbon steel and cast iron has good corrosion resistance, but it is not suitable for high-speed flow of sulfuric acid, is not used as a pump valve materials; Common stainless steel such as 304 (0Cr18Ni9), 316 (0Cr18Ni12Mo2Ti) for sulfuric acid medium is also limited use. Therefore, the delivery of sulfuric acid pump valve is usually made of high silicon cast iron (casting and processing difficult), high alloy stainless steel (no. 20 alloy). Fluoroplastic has better sulfuric acid resistance, using fluorine pump (F46) is a more economical choice.

2, hydrochloric acid, most don't hydrochloric acid corrosion resistant metal materials (including all kinds of stainless steel materials), also can only be used for high silicon molybdenum 50 ℃ and below 30% hydrochloric acid. In contrast to metallic materials, most non-metallic materials have good corrosion resistance to hydrochloric acid, so lining rubber pump and plastic pump (such as polypropylene, fluoroplastic, etc.) is the best choice for transporting hydrochloric acid.

3, nitric acid general metal corrosion and damage, mostly in nitric acid was quickly is the most widely used nitric acid resistant stainless steel material, all on room temperature the concentration of nitric acid have good corrosion resistance, it is important to note that the molybdenum stainless steel (e.g., 316, 316 l) of nitric acid corrosion resistance not only no better than ordinary stainless steel (e.g., 304, 321), sometimes even less. For high temperature nitric acid, usually titanium and titanium alloy materials.

4, acetic acid it is one of the most corrosive substances in organic acid, ordinary steel in all concentration and temperature of acetic acid will seriously corrosion, stainless steel is an excellent anti-acetic acid material, molybdenum-containing 316 stainless steel can also be applied to high temperature and dilute acetic acid steam. For high temperature high concentration acetic acid or contain other corrosive medium such as demanding, can choose high alloy stainless steel pump or fluoroplastic pump.

5, alkali (sodium hydroxide) steel is widely used in under 80 ℃, 30% concentration of sodium hydroxide solution, there are also many factory under 100 ℃, 75% still USES the ordinary steel, while the corrosion increases, but the economy better. The corrosion resistance of ordinary stainless steel to lye has no obvious advantages over cast iron, and stainless steel is not recommended as long as a small amount of iron is allowed in the medium. For the high temperature lye mostly titanium and titanium alloy or high alloy stainless steel.

6, ammonia (ammonia hydroxide) most of the metal and non-metal in liquid ammonia and ammonia water (ammonia hydroxide) corrosion is very minor, only copper and copper alloy is not suitable for use.

7, salt water (sea water) ordinary steel in sodium chloride solution and sea water, salt water corrosion rate is not too high, generally must use paint protection; All kinds of stainless steel also have very low uniform corrosion rate, but may cause local corrosion due to chloride ions, usually 316 stainless steel is better.

8, alcohols, esters, ketones, ethers, common alcohol medium such as methanol, ethanol, ethylene glycol, propylene glycol, ketone medium such as acetone, butanone, there are all kinds of methyl esters medium, ethyl ester, ethers media such as methyl ether, ethyl ether, butyl ether, their basic no corrosive, commonly used materials are applicable, the specific selection should also according to the requirements of the dielectric properties and related make reasonable choice. It is also worth noting that ketone, ester, ether on a variety of rubber solubility, to avoid errors in the selection of sealing materials.