Mechanism
How VCI emitters work in a sealed enclosure
Emitters carry a reservoir of corrosion inhibitor chemistry in a porous foam, tablet, chip, strip, pouch or cup. In a closed air space, inhibitors leave the carrier and enter the enclosure atmosphere. Molecules diffuse until they adsorb on metal. The adsorbed layer is molecular-scale: dry, invisible, and typically dissipates after the enclosure is opened and ventilated.
1. Release. Inhibitor leaves the emitter into package or cabinet air at a controlled rate for the grade.
2. Diffusion. Vapour moves through free volume and into recesses that oil or grease never reach uniformly.
3. Adsorption. Molecules bind to clean metal and interrupt electrochemical corrosion paths.
4. Maintenance. As long as the space stays closed and product capacity remains, concentration supports protection.
Emitters do not create their own sealed envelope. A bag, film liner, crate lid, cabinet door or housing must keep the treated air from continuously exchanging with outdoor humidity. Open shelves defeat the design assumption. Science detail: how VCI works.
Industry guidance for vapour reach often keeps VCI material within roughly 300 mm of metal surfaces for reliable delivery; closer is better. Very large voids need more emitters, foam pads, or a combination of film liners plus emitters so concentration is not starved.