VCI stands for volatile corrosion inhibitor. VCI film, paper or emitters release a vapour that settles on metal surfaces inside a closed package and forms a very thin layer that blocks the reactions that cause rust.
It protects surfaces the vapour can reach, including holes and recesses that oil cannot easily coat. It does not need to be cleaned off before use, which is why it suits machined parts and assembled machines.
Forms you will see
- VCI film is polyethylene with the inhibitor built in, used as bags, shrouds and stretch wrap for whole machines.
- VCI paper is used to interleave or wrap smaller parts such as gears, shafts and turned components.
- VCI emitters are small pouches or foam pieces placed inside panels, gearboxes or electrical cabinets to cover enclosed spaces.
- VCI oils and sprays combine a liquid film with vapour action, for surfaces that need both.
What makes it work, and what makes it fail
The vapour needs a closed space to build up. An open wrap, a torn bag or a gap at the base lets it escape, and protection falls away. Each product also has a limited distance over which it works, so a large machine may need emitters inside cavities as well as an outer shroud.
Parts must go in clean and dry. VCI slows corrosion but cannot remove rust that is already present, and it struggles against sweat, coolant or salt left on the surface. Fingerprints on bright steel are a common source of later rust spots.
Chemistry matters too. Some VCI products are made for ferrous metals and can mark copper, brass or certain coatings. Multi-metal grades exist for mixed assemblies. Ask the factory which grade it uses and check the supplier's data sheet for compatible metals.
Protection also has a time limit set by the product, the sealing and the climate. If your machine may sit in storage after arrival, ask for the rated protection period in writing and plan to rewrap or inspect it.
VCI film also loses strength if it is stored open or for too long before use. Ask the factory to keep rolls sealed and to use stock within the maker's shelf life. Once a machine is unpacked at your site, the protection stops, so plan installation soon after opening.
VCI is one layer, not the whole answer
On a long voyage, a container can swing between hot days and cool nights, and moisture condenses on cold steel. VCI works best with rust preventive on precision surfaces, desiccant inside the wrap and dry crate timber. Our guide on preventing rust during sea freight covers the full system, and export packing for machines covers the crate.
Next step
We check that wrapping is sealed and complete before crates are closed, and we photograph it for you. To set a packing standard for your order, book a free sourcing review.