Ammunition corrodes like any other metal assembly, only with higher stakes
A loaded cartridge is a small multimetal package: a brass or brass-plated steel case, a copper or copper-alloy jacket, a steel or lead core, a primer cup and a crimp. Store it in a humid warehouse, ship it through a tropical port, or leave it in a magazine that sweats every night, and the same galvanic and atmospheric corrosion that attacks a machined part attacks the case. On ammunition the consequences go beyond appearance. Corroded cases can fail to chamber or extract, and Cortec notes that deteriorating propellant charges stored in hot, humid conditions carry a real safety risk.
Cortec published a release at the end of August on a paper product that has been quietly solving this for more than 25 years, and it is one we stock: CorShield VpCI-146.
What the two case histories show
Both of the field records Cortec cites are published Cortec case histories, so we can describe them directly.
| Case history | Application | What was done | Result |
|---|---|---|---|
| Cortec Case History #879 | Ammunition manufacturer in Southeast Asia, 12-gauge shotgun shells | Shells were oxidizing in storage. The plant cut VpCI-146 paper into pieces and placed one in each carton before sealing. | Corrosion stopped. The practice has been in continuous use for more than ten years. |
| Cortec Case History #105 | Defense research agency, 105 mm cartridge cases and charge bags in a tropical climate, starting 1998 | VpCI-146 paper added to the storage packaging. | Prevented corrosion-related deterioration of the cases and charges and, by Cortec’s account, avoided the cost and risk of replacing degraded stock. |
The method in both cases is about as simple as packaging gets. No oil, no dip tank, no desiccant that has to be checked and swapped, and nothing to wipe off before the round is used. The paper goes in, the box closes, and the inhibitor vapor does the work.
Why VpCI-146 fits ammunition, and what else it fits
CorShield VpCI-146 is a natural kraft paper coated with a multimetal vapor phase corrosion inhibitor. Inside a closed carton the paper releases inhibitor molecules that condense on every metal surface in the package, including the inside of a case mouth or under a crimp where a liquid rust preventative would never be applied. When the carton is opened the layer dissipates. Cortec’s published data list carbon steel, brass, copper, aluminum alloys and solder among the metals protected, which covers essentially every metal in a cartridge.
Three details matter for a defense or sporting-ammunition buyer:
- Nothing transfers to the product. There is no oil, wax or film. The paper is dry to the touch and leaves no residue on cases, primers or propellant packaging.
- It is a USDA Certified Biobased Product made from recycled content, and it is repulpable, so it does not create a disposal problem at the depot or the range.
- It works by air space, not by contact. A single piece in a sealed carton protects everything in that carton. Cortec’s sizing rule for VCI paper is roughly one square foot of paper per three square feet of metal surface, or one square foot per half cubic foot of enclosed void, which is why a cut sheet per box is usually enough.
The same properties make VpCI-146 the default choice for a lot of non-defense work we see in the Midwest: interleaving stampings, wrapping machined brass and copper fittings, lining cartons of fasteners, and protecting firearms components and reloading brass between operations. Where the paper also has to resist moisture from outside, VpCI-144 adds a water-resistant barrier coating on one side. Where the parts are electronics or primers sensitive to static, EcoSonic ESD paper adds static dissipation.
A note on the front end of the process
VCI packaging assumes the metal goes in clean and dry. For ammunition and firearms component manufacturers that means the cases, links, magazines or machined parts coming off the line need a proper wash and dry before they are boxed. A Build-All or Magido aqueous parts washer with a heated rinse and blow-off is the usual answer for machined brass and steel components, and it pairs well with an aqueous detergent that carries its own short-term corrosion inhibitor so parts do not flash rust between the washer and the packaging bench.
Which products
- CorShield VpCI-146 paper sheets, 12 x 24, 24 x 24 and 36 x 36, plus rolls in 35 lb and 60 lb basis weights
- VpCI-144 moisture-barrier VCI paper for humid storage
- EcoSonic ESD VCI paper for static-sensitive components
- VpCI-126 Blue zip-close bags for components, magazines and small assemblies
- Desicorr VpCI pouches where desiccant is already specified and VpCI can be added in the same unit
- MilCorr shrink film for pallets and crates going into outdoor or long-term storage
The VpCI product selection guide matches each metal and storage environment to the right paper, film or emitter, and our compatibility charts cover the oils and elastomers that may share the package.
Talk to us
Solvent Recycling Systems is an authorized Cortec distributor with VpCI-146 in stock in Illinois, and we already quote federal and defense accounts. If you need a specification sheet, a cut-size quote or help writing VCI paper into a storage procedure, contact us.
Sources: Cortec press release of August 31, 2026; Cortec Case History #879; Cortec Case History #105.