Corrosion-resistant centrifugal pump selection, corrosion-resistant centrifugal pump how to choose
October 26, 2022
First of all let us understand what is corrosion: Corrosion can be divided into two categories of wet corrosion and dry corrosion. Wet etching refers to the corrosion of metallic materials in the presence of water while dry etching refers to corrosion in dry gases in the absence of liquid water. As the atmosphere generally contains water, chemical processes often deal with a variety of aqueous solutions, so wet etching is the most common, but the high temperature operation of dry corrosion hazards can not be ignored. The pump industry is exposed to the first wet corrosion.
What is wet corrosion: is the corrosion of metal in aqueous solution is an electrochemical reaction. In the metal surface to form an anode and cathode isolation of the corrosion of the cell, the metal loses electrons in solution, into a positively charged ions, which is an oxidation process that is the anode process. In the meantime, there are plenty of opportunities for the electrons to be neutralized by some kind of material in the solution when contacting the metal surface of the aqueous solution. The process of neutralizing the electrons is the reduction process, ie, the cathodic process. Common cathode processes are aerobic reduction, hydrogen release, oxidant is reduced and precious metal deposition. With the progress of the etching process, in most cases, the cathodic or anodic processes will be blocked by the corrosion products of the solution ions, causing the diffusion to be blocked and the corrosion rate to be slower. This phenomenon is called polarization. The corrosion of the metal follows the polarization Slow down.
According to statistics, wet corrosion is one of the most troublesome hazards for users in the chemical industry. Slight carelessness can damage equipment and lead to accidents or even catastrophes. According to Bo Yu pump technology statistics, about 60% of the destruction of chemical equipment is caused due to corrosion, so in the selection of corrosion-resistant pumps, we must first pay attention to the scientific material selection. There is often a misunderstanding that stainless steel is a "universal material," regardless of the media and environmental conditions are held stainless steel centrifugal pump, which is very dangerous. The following for some common chemical media to talk about the selection of corrosion-resistant centrifugal pump points:
1. Sulfuric acid medium As a strong corrosive medium, sulfuric acid is a very broad use of important industrial raw materials. Different concentrations and temperatures of sulfuric acid on the corrosion of materials vary greatly, for the concentration of more than 80%, the temperature is less than 80 ℃ of concentrated sulfuric acid, carbon steel and cast iron has good corrosion resistance, but it is not suitable for high-speed flow of sulfuric acid, Not suitable for pump valve material; common stainless steel such as 304 (0Cr18Ni9), 316 (0Cr18Ni12Mo2Ti) 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) manufacturing, but its processing is difficult and expensive, so people are not optimistic. Fluoroplastics alloy has very good resistance to sulfuric acid. It is the patented material of Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences. Our company introduced the patented technology in 1985 and the earliest use it to develop and produce corrosion-resistant chemical pump. After the experiment of the Chinese Academy of Sciences, There is no chemical medium to react with it, so using a fluorine-based pump (F46) is a more economical option. Boyu company applicable products include: IHF fluorochemical chemical pump, FSB fluoroplastic centrifugal pump, IGF-lined pipeline pump, PF-type centrifugal pump corrosion, CQB-F-type fluorine plastic magnetic pump.
2. Hydrochloric acid solution Most metal materials are resistant to hydrochloric acid corrosion (including a variety of stainless steel materials), molybdenum high ferrosilicon can only be used for 50 ℃, hydrochloric acid below 30%. In contrast to metallic materials, the vast majority of non-metallic materials have good corrosion resistance to hydrochloric acid, so lined rubber pumps and plastic pumps (such as engineering plastics, fluoroplastics, etc.) are the best choice for the delivery of hydrochloric acid. Boyu company applicable products: fluoride plastic chemical pump series can be.
3. Nitric acid Most metals are mostly corrosive in nitric acid corrosion damage, stainless steel corrosion-resistant centrifugal pump is the most widely used nitric acid centrifugal pump, all concentrations of nitric acid at room temperature have good corrosion resistance, it is worth mentioning that with The corrosion resistance of nitric acid to molybdenum stainless steel (such as 316,316L) is not only inferior to ordinary stainless steel (such as 304,321), sometimes even worse. For high temperature nitric acid, usually using fluorine plastic alloy material. Boyu company applicable products include: IHF fluorochemical chemical pump, FSB fluoroplastic centrifugal pump, IGF-lined pipeline pump, PF-type centrifugal pump corrosion, CQB-F-type fluorine plastic magnetic pump.
4. Acetic acid It is one of the most corrosive substances in organic acids. Ordinary steel will be seriously corroded in all concentrations and temperatures of acetic acid. 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. For high temperature and high concentration of acetic acid or other corrosive media and other harsh requirements, the choice of high-alloy stainless steel magnetic pump or fluorine plastic chemical pump such as CQB-type stainless steel magnetic pump, CQ-type magnetic drive pump, stainless steel pipe centrifugal pump, stainless steel chemical pump.
5. Alkali (sodium hydroxide) Generally corrosive is not very strong, but the general alkaline solution will have a crystal, so the choice of configuration silicide, graphite 169 mechanical seal FSB-type fluoroplastic alloy centrifugal pump.
6. Ammonia (ammonia hydroxide) Most metals and non-metals in liquid ammonia and ammonia (ammonia hydroxide) corrosion are minor, only copper and copper alloy should not be used. Most of the company's products for ammonia and ammonia transport. Such as IHF Fluorine plastic chemical pump, FSB fluoroplastic centrifugal pump, IGF-lined fluorine pipeline pump, PF-type corrosion-resistant centrifugal pump , CQB-F type fluorine plastic magnetic pump, CQF type plastic magnetic magnetic pump better.
