Which DOT specification uses stainless steel as the tank material?

Answer: B — DOT 407

Materials chosen for a tank are driven by how the cargo interacts with the metal. Corrosive liquids can attack many common metals, so tanks carrying them need a material that resists chemical attack, stays strong, and is easy to clean. DOT 407 is the specification for corrosive liquids, so its tanks are designed with corrosion resistance in mind. Stainless steel is a common choice for these tanks because it withstands acids and caustics, reducing the risk of pitting or leaks and making decontamination easier. That’s why stainless steel as the tank material is associated with this specification. Other specifications on the list cover different types of cargos (noncorrosive fuels, other non-pressurized liquids, etc.) and typically use materials like carbon steel or aluminum with appropriate linings, rather than stainless steel.