Selection of materials for chemical pumps for common acid and alkali liquids

　　According to statistics, about 60% of chemical equipment damage is caused by corrosion, however, chemical equipment, especially chemical pumps, is an indispensable key equipment for conveying chemical liquids, the first thing to pay attention to the selection of pumps, different chemical media need to choose different materials and pump type, we will look at the selection of special chemical media pumps key points.

　　Sulfuric acid H2SO4

　　As one of the highly corrosive media, sulfuric acid is a widely used important industrial raw materials.

　　In different concentrations and temperatures, sulfuric acid corrosion of materials is completely different, although the concentration of more than 80%, the temperature is less than 80 ° C concentrated sulfuric acid on carbon steel and cast iron has good corrosion resistance, but they are not suitable for high-speed flow of sulfuric acid. Ordinary stainless steels such as 304 (0Cr18Ni9) and 316 (0Cr18Ni12Mo2Ti) have limited effectiveness in conveying sulfuric acid media due to the fluidity of sulfuric acid.

　　Although it is made of high silica cast iron (difficult to cast and process) and high alloy stainless steel (alloy 20), it is difficult and costly to process, and it does not have a promising future considering the cost and processing difficulty.

　　Fluoroplastics have good resistance to sulfuric acid and corrosion, so using fluorine lined pumps is a more economical choice for dilute acid and sulfate solutions, RMD, RMI, IMC fluorine lined magnetic pumps, IHF chemical centrifugal pumps, RMZ, IMZ fluorine lined self-priming magnetic pumps, FZB fluorine lined self-priming pumps series, etc, all of which are a more practical, economical, safe and cost-effective choice.

　　Hydrochloric acid HCL

　　Most metallic materials (including various stainless steel materials) are not resistant to hydrochloric acid corrosion, and high silica iron containing molybdenum can only be used in hydrochloric acid at less than 50°C and 30%.

　　However, most non-metallic materials have good corrosion resistance to hydrochloric acid, so fluorine lined pumps and plastic pumps (e.g., engineering plastics, fluoroplastics, etc.) such as RMD, RMI, IMC fluorine lined magnetic pumps, and RMZ, IMZ fluorine lined self-priming magnetic pumps are ideal for conveying hydrochloric acid at room temperature.

　　Nitric acid HNO3

　　Most metals are susceptible to corrosion by nitric acid, but the exception is stainless steel, which is the most widely used nitric acid-resistant material with good corrosion resistance. At room temperature, stainless steel is essentially unaffected by any concentration of nitric acid.

　　More interestingly, the corrosion resistance of common stainless steel (e.g. 304, 321) to nitric acid is better than that of molybdenum-containing stainless steel (e.g. 316, 316L). Therefore, ordinary stainless steel can be used for room temperature nitric acid, while for high temperature nitric acid, fluoroplastic materials are usually used.

　　Room temperature dilute nitric acid: stainless steel pumps (RMD, RMI, IMC stainless steel magnetic pumps, thermal insulation magnetic pumps, high temperature magnetic pumps and IH chemical pump series) are good choices.

　　High temperature dilute nitric acid: steel fluorine lined pumps (RMD, RMI, IMC fluorine lined magnetic pumps, RMZ, IMZ fluorine lined self-priming magnetic pumps, IHF chemical pumps, etc.) are ideal.

　　Hydrofluoric acid HF

　　Hydrofluoric acid is one of the highly corrosive media, characterized by volatility and toxicity. Therefore, it puts forward higher requirements on the materials and process technology of pump manufacturing.

　　The corrosive effect of hydrofluoric acid on carbon steel and lead is similar to that of sulfuric acid. In most strong acids, hydrofluoric acid also has some unique corrosion characteristics. Tantalum, titanium and zirconium have good corrosion resistance to most acids, but not to hydrogen fluoride. Any silicon-containing material should not be used with hydrofluoric acid. At room temperature, all plastics are suitable for diluting hydrofluoric acid. For hydrofluoric acid at temperatures <65°C and concentrations <70%: RMD, RMI, IMC fluorine-lined magnetic pumps and IHF chemistry pumps are the more economical choice.

　　Due to the easily vaporized nature of hydrofluoric acid, some manufacturers store IHF underground below the pump level. In this case, RMZ, IMZ fluorine-lined self-priming magnetic pumps, submersible canned pumps, etc. become ideal hydrofluoric acid special pumps (hydrofluoric acid pump).

　　Phosphoric acid H3PO4

　　Phosphoric acid is a strong corrosive medium. The selection of pure acid is relatively simple, but phosphoric acid often contains some impurities, such as fluoride, chloride, sulfuric acid and so on. This increases the complexity and difficulty of selection. We should understand the impurities in phosphoric acid when choosing.

　　Ordinary steel is not resistant to phosphoric acid. The best materials for phosphoric acid resistance are chromium, nickel, and molybdenum (316) stainless steel and high-alloyed steel (alloy 20), which can be used for acids with boiling points below 85%. However, many fluoroplastics have excellent corrosion resistance to phosphoric acid and phosphate solutions. The choice is based on the concentration and temperature range of the plastic's resistance to phosphoric acid.

　　Therefore, chemical pumps made of different materials can be selected according to different situations, such as RMD, RMI, IMC stainless steel magnetic pumps, RMD, RMI, IMC fluorine-lined magnetic pumps, RMZ, IMZ fluorine-lined self-priming magnetic pumps, IHF chemical pumps and so on. All these methods are feasible, but fluorine lined magnetic pumps are lower cost and more practical.

　　Sodium hydroxide NaOH

　　It is not very corrosive at room temperature, but the situation is different at high temperatures and under stress. It is severely corrosive to many metals and crystallizes in most alkaline solutions.

　　Well, the following plastics are corrosion resistant at room temperature and at low concentrations, such as polypropylene, which is resistant to alkaline solutions of less than 70% below 100°C. Therefore, graphite silicide mechanical seals and IHF chemical centrifugal pumps are available. IMC, RMD, RMI fluorine-lined magnetic pumps, self-priming pumps and so on.

　　In a word, fluorine plastic materials have become the main materials for chemical pumps and equipment used for conveying various acid and alkali liquids. They not only have good corrosion resistance, but also low price.