46 CFR § 153.556 - Special requirements for sulfuric acid and oleum.
(a) Except as prescribed in paragraphs (b) and (c) of this section, containment systems carrying sulfuric acid, oleum, or contaminated sulfuric acid are approved by the Commandant (CG-ENG) on a case by case basis.
(b) A containment system carrying sulfuric acid may be:
(1) Made of unlined steel if the cargo composition is between 70 and 80 or between 90 and 100 percent acid by weight;
(2) Lined with lead if the cargo composition does not exceed 96 percent acid by weight; or
(3) Lined with natural rubber or neoprene if the cargo composition does not exceed 51 percent acid by weight.
(c) A containment system for oleum may be of unlined steel if the concentration of free sulfur trioxide in the oleum exceeds 20 percent by weight.