What is VCI?
VCI is a vapor corrosion inhibitor; this is a class of chemical compounds that emit a rust-inhibiting vapor into the air to stop corrosion on metal surfaces. Typically a packaging material (like paper or poly film) is the carrier for the VCI chemicals, but they can also be delivered through plastic, paper, or foam emitters.
Corrosion happens when an electrolyte (water, oxygen, etc.) is present on the surface of a metal. The corrosion process begins when electrons flow through the electrolyte from high energy areas to low energy areas of the metal.
The protective vapors of the VCI attach themselves to a metal surface to form an invisible film only a few molecules thick to protect metal from corrosive attacks. They are attracted to the charged surface of the metal by virtue of their polar orientation. Certain types of VCIs can work for years to prevent corrosion.
How VCI works – scientifically speaking
The VCI molecules align on the surface of the metal to a depth of 3 to 5 molecules. This layer of molecules passivates the charged surface and creates a barrier that prevents oxidation. The corrosion cell (the flow of electrons in the metal and the flow of ions in the electrolytic surface layer) is unable to establish itself. Corrosion is halted.
And the best part? Airtight packing is not required!
From strictly a corrosion inhibitor standpoint, paper has long been a better choice due to the way that the VCI is embedded into the paper. However, VCI poly film has some significant advantages, as well, because it provides a moisture barrier in addition to corrosion resistance, and is easiest to use as products can be simply slipped into a VCI polybag.
The VCI molecules migrate into recesses and hard to reach areas on even the most complex shapes. The molecules build up on the metal surface until a continuous barrier has formed on the metal part.
The chemicals in VCI products are volatile. When metals are wrapped or packaged in VCI, the chemicals volatilize in the packaging environment, forming a protective molecular layer on the surface of the metal. This protective layer serves as a barrier, preventing moisture, salt, dirt, oxygen, and other corrosion causing materials from depositing directly on the metal and causing rust and corrosion.
The corrosion inhibitors are extruded right into the polyethylene film, not superficially applied. As a result, the volatile and contact inhibitors provide long-term corrosion protection for the most intricate and hard-to-reach surfaces. The corrosion protection is clean, non-discernible, with no strong chemical odor.
Simply store or ship metal parts in VCI packaging. When the parts are unwrapped, the protective layer immediately begins to dissipate. The metal parts are clean, corrosion-free and ready to use. No washing, dipping or cleaning is necessary.
VCI film is transparent for easy inspection and identification of parts. It will not affect the performance of the protected metal, and the parts are ready to use immediately after removal from the packaging without cleaning.