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Advices for materials option in chemical industry
2024.08.06
sulphuric acid
As one of the strong corrosive media, sulfuric acid is an important industrial raw material with a wide range of uses. For 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, but it is not suitable for high-speed flow of sulfuric acid, and is not suitable for use as a material for pump valves; Ordinary stainless steels such as 304 (0Cr18Ni9) and 316 (0Cr18Ni12Mo2Ti) also have limited use for sulfuric acid media. Therefore, pumps and valves for transporting sulfuric acid are usually made of high-silicon cast iron (difficult to cast and process) and high-alloy stainless steel (alloy 20). Fluoroplastics have good resistance to sulfuric acid, and fluorine-lined valves are a more economical choice.
hydrochloric acid
Most metal materials are not resistant to hydrochloric acid corrosion (including various stainless steel materials), and molybdenum-containing ferrosilicon can only be used for hydrochloric acid below 50°C and 30%. Contrary to metal materials, most non-metallic materials have good corrosion resistance to hydrochloric acid, so lined rubber valves and plastic valves (such as polypropylene, fluoroplastics, etc.) are the best choice for conveying hydrochloric acid.
acetic acid
It is one of the most corrosive substances in organic acids, ordinary steel will be severely corroded in acetic acid at all concentrations and temperatures, stainless steel is an excellent acetic acid resistant material, and molybdenum-containing 316 stainless steel can also be used for high temperatures and dilute acetic acid steam. For high temperature, high concentration acetic acid or other corrosive media and other harsh requirements, high-alloy stainless steel valves or fluoroplastic valves can be selected.
nitric acid
Most of the general metals are rapidly corroded and destroyed in nitric acid, stainless steel is the most widely used nitric acid resistant material, and has good corrosion resistance to all concentrations of nitric acid at room temperature, it is worth mentioning that molybdenum-containing stainless steel (such as 316, 316L) is not only not better than ordinary stainless steel (such as 304, 321), sometimes even inferior. For high-temperature nitric acid, titanium and titanium alloy materials are usually used.
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