46 CFR §188.10-23

1. (a)This term includes those acids, alkaline caustic liquids, and other corrosive liquids which, when in contact with living tissues, will cause severe damage of such tissues, by chemical action; or in case of leakage, will materially damage or destroy other freight by chemical action, or are liable to cause fire when in contact with organic matter or with certain chemicals.
2. (b)A corrosive substance may be:
   1. (1)Solid, such as iodine; or,
   2. (2)Liquid, such as acids, or caustic soda solution; or,
   3. (3)Gaseous, such as chlorine or sulfur dioxide.