About common acid-base liquid chemical pump material selection
According to statistics, about 60% of the damage to chemical equipment is caused by corrosion. However, chemical equipment, especially chemical pumps, are indispensable and key equipment for transporting chemical liquids. When selecting pumps, we must first pay attention to the material selection
Different chemical media
Sulfuric acid H2SO4
As one of the highly corrosive media, sulfuric acid is an important industrial raw material with a wide range of uses.
The corrosion of materials by sulfuric acid at different concentrations and temperatures is quite different. Although concentrated sulfuric acid with a concentration of more than 80% and a temperature of less than 80°C, carbon steel and cast iron have good corrosion resistance
Although it is made of high-silicon cast iron (which is difficult to cast and process) and high-alloy stainless steel (No. 20 alloy), it is difficult to process and expensive. Considering the cost and difficulty, it is not promising.
Fluorine plastic has good resistance to sulfuric acid and good corrosion resistance, so using a fluorine-lined pump is a more economical choice
Hydrochloric acid HCL
Most metal materials are not resistant to hydrochloric acid corrosion (including various stainless steel materials), and molybdenum-containing high-silicon ferrosilicon can only be used in hydrochloric acid below 50°C and 30%.
However, most non-metallic materials have good corrosion resistance to hydrochloric acid. Therefore, fluorine-lined pumps and plastic pumps (such as engineering plastics, fluoroplastics, etc.) such as: RMD, RMI, IMC fluorine-lined magnetic pumps, RMZ, IMZ fluorine-lined self-priming magnetic pumps are ideal choices for transporting normal temperature hydrochloric acid.
Nitric acid HNO3
Most metals are easily corroded by nitric acid, but stainless steel is an exception. It is the most widely used nitric acid-resistant material and has good corrosion resistance. It is basically unaffected by any concentration of nitric acid at room temperature.
What’s more interesting is that the corrosion resistance of ordinary stainless steel (such as 304, 321) to nitric acid is better than that of molybdenum-containing stainless steel (such as 316, 316L). Therefore, ordinary stainless steel can be used for nitric acid at room temperature, while for high-temperature nitric acid, usually Fluoroplastic material.
Dilute nitric acid at room temperature: Stainless steel pumps (RMD, RMI, IMC stainless steel magnetic pumps, thermal insulation magnetic pumps, high-temperature magnetic pumps, and IH chemical pump series) are all good choices.
High-temperature dilute nitric acid: steel-lined fluorine pumps (RMD, RMI, IMC fluorine-lined magnetic pumps, RMZ, IMZ fluorine-lined self-priming magnetic pumps, IHF chemical pumps, etc.) are ideal.
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Hydrofluoric acid HF
Hydrofluoric acid is one of the highly corrosive media and has special characteristics such as easy vaporization and toxicity. Therefore, it places 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. Among most strong acids, hydrofluoric acid also has some unique corrosive properties. Tantalum, titanium, and zirconium, which have excellent corrosion resistance to most acids, are not resistant to hydrogen fluoride. Acid, any material containing silicon cannot be used with hydrofluoric acid. A variety of plastics are suitable for diluting hydrofluoric acid under normal temperature conditions. Hydrofluoric acid with a temperature <65°C and a concentration <70%: RMD, RMI, IMC fluorine-lined magnetic pumps, and IHF chemical pumps are all more economical choices.
Due to the easy vaporization characteristics of hydrofluoric acid, some manufacturers store IHF underground below the pump liquid level. At this time, RMZ, IMZ fluorine-lined self-priming magnetic pumps, submersible canned pumps, etc. have become ideal hydrofluoric acid special pumps (hydrogen Fluoric acid pump).
Phosphoric acid H3PO4
Phosphoric acid is a highly corrosive medium. The selection of pure acid is relatively simple, but phosphoric acid often contains some impurities, such as fluoride, chloride, sulfuric acid, etc. This makes the selection more complex and difficult. We should understand the impurities in phosphoric acid when selecting.
Ordinary steel is not resistant to phosphoric acid. The best phosphoric acid-resistant materials are chromium, nickel, molybdenum (316) stainless steel, and high alloy steel (No. 20 alloy), which can be used for acids with boiling points below 85%. However, many fluoroplastics have excellent corrosion resistance to phosphoric acid and phosphate solutions. When selecting, the selection can be based on the concentration and temperature range of the plastic's resistance to phosphoric acid.
Therefore, chemical pumps of different materials can be selected according to different situations, such as RMD, RMI, IMC stainless steel magnetic pump, RMD, RMI, IMC fluorine-lined magnetic pump, RMZ, IMZ fluorine-lined self-priming magnetic pump, IHF chemical pump, etc. It is feasible, but the fluorine-lined magnetic pump is less expensive and more practical.
Sodium Hydroxide NaOH
It is not very corrosive at room temperature, but the situation is different at high temperatures and in the presence of stress. It is severely corrosive to many metals, and most alkaline solutions will crystallize.
Then, the following types of plastics have corrosion resistance under normal temperature and low concentration conditions, such as polypropylene, which can withstand less than 70% alkali solution up to 100°C. Therefore, mechanical seals made of siliconized graphite and IHF chemical centrifugal pumps can be selected. , IMC, RMD, RMI fluorine-lined magnetic pumps, self-priming pumps, etc.
In summary, fluoroplastic materials have become the main material of choice for chemical pumps and equipment used for transporting various acid-base liquids. They not only have good corrosion resistance but are also affordable.
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