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 material that qualifies as a Limited Quantity air or Limited Quantity surface transportation is permissible. Mailable corrosives are also 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 (UN2809), and devices containing metallic mercury, such as thermometers, barometers, and sphygmomanometers (i.e., blood pressure meters).
As a rule, liquid corrosives are limited to 15 percent solution or less as stated in 348.2, unless otherwise specified below. Mailable corrosives include the following:
- Acetic Acid (UN2790). Acceptable in solutions that can qualify as a Limited Quantity air material or Limited Quantity surface material, contains less than 80 percent acid, and does not exceed 1 pint. 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. For nickel-metal hydride batteries in sea transportation, see 49 CFR 122.102, Special Provision 130. Packaging requirements in DMM 601.1-7 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. 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 a Limited Quantity air material or Limited Quantity surface material. Packaging Instruction 8A in Appendix C must be followed.
- Sulfuric Acid (UN2796). Acceptable only in solutions of 25 percent or less acid that can qualify as a Limited Quantity air or Limited Quantity surface material. Packaging Instruction 8A in Appendix C must be followed.
- Dyes (UN2801, UN3147). Acceptable if the dyes can qualify as Limited Quantity air material or Limited Quantity surface material. 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 a Limited Quantity air material or Limited Quantity surface material. 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).
- Manufactured devices that contain small amounts of mercury (UN3506). Compact Fluorescent Lamps (CFL) and similar consumer devices containing minute amounts of mercury are mailable by air or surface only when each device, article, or apparatus contains 100 milligrams (mg) (0.0035 ounce) or less of mercury (less than a grain of salt) and each mailpiece contains no more than 1 gram (g) (0.035 ounce) of mercury. Mercury contained in devices categorized under UN3506 typically exists in a vaporized state — no metallic mercury will be visible in UN3506 devices. See Packaging Instruction 8C in Appendix C for mailing details.
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.
All labels and text markings must be placed on the address side of the mailpiece unless specified in 221.1 and 325.1. Parcels containing mailable corrosive material must be marked as follows:
- For air transportation, a mailpiece containing a mailable corrosive material must bear the DOT square-on-point marking. 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 must also bear the appropriate approved DOT Class 8 hazardous material warning label, the identification number, and the proper shipping name. A properly completed shipper’s declaration for dangerous goods must be affixed to the outside of the mailpiece.
- For surface transportation, parcels containing mailable Class 8 materials must be plainly and durably marked on the address side with an approved DOT Limited Quantity surface mark (see 325.4). Surface shipments bearing the Limited Quantity surface marking are not required to include the proper shipping name and identification number. A shipper’s declaration for dangerous goods is not required for mailable Class 8 corrosives sent via surface transportation.
- When the DOT square-on-point markings are used, markings must be durable, legible, and readily visible, and 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.