What is vci (vapour corrosion inhibitor)?
VCI is a corrosion inhibitor that vaporises from a paper, film or emitter and condenses as an invisible protective layer on every metal surface inside a sealed package — including blind holes and internal bores a liquid coating can never reach. It requires an enclosed volume to work.
Also called: vapour phase inhibitor, VPI
The inhibitor sublimes slowly, saturates the air in the package, and adsorbs onto metal as a molecular film. Because it works through the vapour phase, geometry stops mattering — a complex casting is protected as completely as a flat plate.
The absolute requirement is enclosure. VCI in an open crate does nothing; the vapour disperses. Packaging must be genuinely sealed, and the parts must be clean and dry going in, because VCI cannot protect metal under a layer of moisture or salt.
VCI and oil-based preventives are complementary rather than competing: exposed faces get the film, internal passages get the vapour, and the whole assembly goes into a sealed bag.
