Which material is not suitable for cryogenic tanks due to brittleness?

Carbon steel is not suitable for cryogenic tanks primarily due to its susceptibility to brittleness at low temperatures. At cryogenic temperatures, the properties of carbon steel change, resulting in reduced ductility and toughness. This brittleness can lead to fractures and catastrophic failures in storage tanks designed to hold cryogenic fluids.

In contrast, materials like aluminum, stainless steel, and copper can maintain their integrity and remain ductile even at extremely low temperatures. For instance, aluminum is often used in cryogenic applications because of its excellent resistance to temperature fluctuations, while stainless steel has enhanced corrosion resistance and toughness at low temperatures. Copper, although not commonly used for large cryogenic tanks, retains ductility at lower temperatures as well. Consequently, when selecting materials for cryogenic tanks, avoiding carbon steel is critical to ensuring the safety and reliability of these structures.