49 CFR §192.475

1. (a)Corrosive gas may not be transported by pipeline, unless the corrosive effect of the gas on the pipeline has been investigated and steps have been taken to minimize internal corrosion.
2. (b)Whenever any pipe is removed from a pipeline for any reason, the internal surface must be inspected for evidence of corrosion. If internal corrosion is found—
   1. (1)The adjacent pipe must be investigated to determine the extent of internal corrosion;
   2. (2)Replacement must be made to the extent required by the applicable paragraphs of §§ 192.485, 192.487, or 192.489; and
   3. (3)Steps must be taken to minimize the internal corrosion.
3. (c)Gas containing more than 0.25 grain of hydrogen sulfide per 100 cubic feet (5.8 milligrams/m 0.3) at standard conditions (4 parts per million) may not be stored in pipe-type or bottle-type holders.