A corrosive is any liquid or solid that causes visible destruction or irreversible alteration in human skin tissue at the site of contact, or a liquid that has a severe corrosion rate on steel. The term “corrosive” includes all items commonly referred to as acids, as well as most batteries.
- International Mail. All corrosives are prohibited.
- Domestic Mail. A corrosive that can qualify as an ORM–D material and be renamed with the proper shipping name, “Consumer Commodity”, is permitted via air or surface transportation subject to the following:
- A liquid mixture must be 1 pint (16 oz) or less and must contain 15 percent or less corrosive material, with the remainder of the mixture not being a hazardous material, unless otherwise specified in 348.22 for a specific corrosive material.
- A solid mixture must be 10 pounds or less per primary receptacle and must contain 10 percent or less corrosive material, with the remainder of the mixture not being a hazardous material, unless otherwise specified for a specific corrosive solid.
Nonmailable corrosives include the following:
- Batteries (UN2794, UN2795) with liquid electrolyte (such as automobile lead acid batteries), except for the nonspillable type allowed under 348.22.
- Nitric Acid (UN2031, UN2032).
- Fuming and Spent Sulfuric Acids (UN1831, UN1832).
- Hydrofluoric Acid (UN1790).
- Mercury, and items containing mercury, including thermometers.
As a rule, liquid corrosives are limited to 15 percent solution or less as stated in 348.2 and DMM 601.10.19, unless otherwise specified below. Mailable corrosives include the following:
- Acetic Acid (UN2790). Acceptable in solutions that qualify as an ORM–D material and contain less than 80 percent acid and do not exceed 1 pint. Only one primary receptacle is permitted per mailpiece. Packaging Instruction 8A must be followed.
- Batteries. Mailable batteries include:
- Common household dry-cell batteries such as sizes AA, AAA, C, D, etc. are generally not regulated as hazardous materials and are therefore mailable. Packaging requirements in DMM 601.1–8 apply.
- A nonspillable wet battery containing liquid electrolyte is permitted to be mailed only if the battery casing is completely sealed to prevent the liquid corrosive from spilling during Postal Service handling, as stated in DMM 601.10.19.4. Nonspillable batteries with UN2800 are prohibited in international mail but may be sent as domestic mail via air or surface transportation when prepared within the conditions of Packaging Instruction 8B in Appendix C.
- For lithium and lithium-ion batteries, see 349.22.
- Hydrochloric Acid (UN1789). Acceptable only in solutions not exceeding 10 percent acid that can qualify as an ORM–D material. Packaging Instruction 8A in Appendix C must be followed.
- Sulfuric Acid (UN2796). Acceptable in solutions of less than 25 percent acid that qualify as an ORM–D material. Mailable liquids must be packed in a primary receptacle not exceeding 1 pint. Only one primary receptacle is permitted per mailpiece. Packaging Instruction 8A in Appendix C must be followed.
- Dyes (UN2801, UN3147). Acceptable if the dyes can qualify as ORM–D materials. Mailable dyes must be packaged as required in 348.3 and Packaging Instruction 8A in Appendix C.
- Photographic Mixtures. Acceptable if the corrosive liquid solutions for preparing photographic processing mixtures can qualify as ORM–D materials. Packaging Instruction 8A in Appendix C must be followed. When these liquids are in securely closed and sealed bottles that are properly cushioned, they may be packed in the same outside shipping container with required amounts of packaged dry chemicals not classified as hazardous materials (provided no dangerous reaction would occur should the contents of the bottles be mixed with the dry chemicals).
Mailable corrosives, both liquids and solids, must meet the applicable requirements in 348.2b and be prepared as required in Packaging Instruction 8A in Appendix C, or as permitted in 348.22.
Parcels containing mailable corrosive material must be marked as follows:
- For air transportation, a mailpiece containing a mailable corrosive material must be plainly and durably marked on the address side with “ORM–D AIR” immediately following or below the proper shipping name (Consumer Commodity). A properly completed shipper’s declaration for dangerous goods must be affixed to the outside of the mailpiece.
- For surface transportation, a mailpiece must be plainly and durably marked on the address side with “Surface Mail Only” and “ORM–D” immediately following or below the proper shipping name (Consumer Commodity). A shipper’s declaration for dangerous goods is not required for mailable Class 8 corrosives.
- Optionally, mailable limited quantity (ORM-D) material may be marked with an approved DOT limited quantity square-on-point marking (see Exhibit 325b). The plain square-on-point marking is used for shipments sent by surface transportation, and the square-on-point marking including the symbol “Y” superimposed in the center is used for shipments sent by air transportation. The following also apply:
- Markings must be durable, legible, and readily visible.
- The marking must be applied on at least one side or one end of the outer packaging. The border forming the square-on-point must be at least 2 mm in width, and the minimum dimension of each side must be 100 mm, unless the package size requires a reduced size marking of no less than 50 mm on each side.
- For surface transportation, the top and bottom portions of the square-on-point and the border forming the square-on-point must be black, and the center must be white or of a suitable contrasting background. Surface shipments containing qualifying ORM-D material bearing the square-on-point limited quantity marking are not required to be marked with the shipping name and identification number.
- For transportation by aircraft, the top and bottom portions of the square-on-point and the border forming the square-on-point must be black, and the center must be white or of a suitable contrasting background. The symbol “Y” must be black, located in the center of the square-on-point, and clearly visible. Mailpieces intended for transport by air must also be marked with the proper shipping name and identification number, and must also display an approved DOT class 8 hazardous material warning label (see Exhibit 325c).