In cryogenic tank construction, is carbon steel typically used?

• A. Yes
• B. No
• C. Sometimes
• D. Depends on the gas stored

Answer: (B)

The key idea is material performance at very low temperatures. Cryogenic tanks must keep their toughness and not crack when exposed to extreme cold. Carbon steel loses significant toughness as temperatures drop, becoming brittle and more prone to fracture, which is unacceptable for containing cryogenic liquids. That’s why carbon steel isn’t typically used for the cryogenic inner vessel. Instead, materials like stainless steels and aluminum alloys are chosen because they retain ductility and strength at cryogenic temps and are compatible with the stored fluids. In some designs, carbon steel may be used for non-cryogenic parts or outer jackets, but the actual cryogenic containment is usually stainless steel or aluminum.