Plates, forgings and forged or rolled fittings, and rolled, forged or extruded bars and shapes for cargo tanks, secondary barriers, and process pressure vessels for a design temperature below −55 °C (−67 °F) and down to −165 °C (−265 °F) must:

(a) Meet § 54.25-10(b)(2), § 54.25-15, or § 54.25-20 of this chapter; or

(b) Be of an aluminum alloy that is specially approved by the Commandant (CG-ENG).