Chemical Pump Material Selection Methods


Published:

Aug 19,2022

As one of the strong corrosive media, sulphuric acid is an important industrial raw material for a wide range of uses. For concentrations above 80% and temperatures less than 80°C, carbon steel and cast iron have good corrosion resistance

Chemical Pump Material Selection Methods

As one of the strong corrosive media, sulphuric acid is an important industrial raw material for a wide range of uses. For concentrations above 80% and temperatures less than 80°C, carbon steel and cast iron have good corrosion resistance, but it is not suitable for high-speed flow of sulphuric acid, not suitable for use as a material for pumps and valves

1.Sulfuric Acid: Sulfuric acid is a highly corrosive substance used extensively in various industries. The corrosion resistance of materials to sulfuric acid varies depending on the concentration and temperature. For concentrations above 80% and temperatures below 80°C, carbon steel and cast iron demonstrate fair corrosion resistance; however, they are unsuitable for high-speed sulfuric acid flow and thus not recommended for use in pump or valve materials. Ordinary stainless steels like 304 (0Cr18Ni9) and 316 (0Cr18Ni12Mo2Ti) also have limited use with sulfuric acid. Therefore, pumps and valves designed for conveying sulfuric acid typically employ materials like high-silicon cast iron (challenging to cast and process) and high-alloy stainless steel (e.g., No. 20 alloy). Fluorine plastics, especially fluorine-lined pumps (F46), offer better resistance to sulfuric acid and are a more economical choice.

2.Hydrochloric Acid: Most metal materials are highly susceptible to corrosion from hydrochloric acid (including various stainless steel materials). High-silicon iron containing molybdenum can only be used for hydrochloric acid concentrations below 30% and at temperatures under 50°C. In contrast, non-metallic materials exhibit good corrosion resistance to hydrochloric acid. Therefore, rubber-lined pumps and plastic pumps (such as polypropylene, fluorine plastics, etc.) are preferred choices for conveying hydrochloric acid.

3.Nitric Acid: The majority of metals suffer rapid corrosion and damage in contact with nitric acid. Stainless steel is the most widely used material resistant to nitric acid across all concentrations and room temperatures. It's noteworthy that molybdenum-containing stainless steels (e.g., 316, 316L) don’t always exhibit better corrosion resistance to nitric acid compared to regular stainless steels (e.g., 304, 321). For high-temperature nitric acid, materials like titanium and titanium alloys are commonly employed.

4.Acetic Acid: As one of the most corrosive organic acids, ordinary steel is highly susceptible to corrosion by acetic acid at all concentrations and temperatures. Stainless steel, particularly molybdenum-containing 316 stainless steel, can be used for high-temperature and dilute acetic acid steam. For highly concentrated or high-temperature acetic acid containing other corrosive media, high-alloy stainless steel pumps or fluorine plastics are recommended.

The article continues similarly for various other chemical substances and their respective corrosiveness and compatibility with different materials used in pump and valve production.

Keyword:

chemical pumps