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 [deg]C (-67 [deg]F) and down to -165 [deg]C (-265 [deg]F) must:
(a) Meet Sec. 54.25-10(b)(2), Sec. 54.25-15, or Sec. 54.25-20 of this chapter; or
(b) Be of an aluminum alloy that is specially approved by the Commandant (CG-ENG). [CGD 74-289, 44 FR 26009, May 3, 1979, as amended by CGD 82-063b, 48 FR 4782, Feb. 3, 1983]