When customers first consider using VCI technology, we are commonly asked, “Do VCI products displace moisture or only protect after surfaces are dry?” This question comes up frequently after parts are washed, rinsed, or exposed to humid environments.

The answer is no. VCI products do not push away, absorb, or neutralize moisture that is already present on a metal surface. Vapor corrosion inhibitors work in the vapor phase by releasing protective molecules into a sealed environment. These molecules adsorb onto metal surfaces and interrupt the electrochemical corrosion process, but they do not remove water.

Because of this, standing water, heavy condensation, or trapped moisture can still lead to corrosion if parts are packaged incorrectly.

How VCI molecules protect metal surfaces

VCI molecules migrate through the enclosed air space inside packaging and attach to exposed metal surfaces. Once adsorbed, they form an invisible protective layer that blocks oxygen, moisture, and contaminants from initiating corrosion. Regarding the protection given, it happens despite the fact that VCI products do not displace moisture.

This protection works best when parts are:

  • Clean and free of corrosive residues
  • Surface dry with no visible water
  • Enclosed in properly sealed VCI packaging

VCI protection begins quickly after enclosure, but it is not a substitute for drying or cleaning steps.

Why surfaces should be dry before VCI packaging

Moisture left on parts can become trapped inside the package. If water remains in direct contact with the metal, corrosion may start before the VCI layer fully establishes itself. Since VCI products do not displace moisture, it’s best to keep surfaces dry.

For best results:

  • Remove standing water after washing or rinsing
  • Allow parts to reach surface dry condition
  • Avoid sealing hot parts that may later condense moisture

Following these steps allows VCI molecules to work as intended and deliver reliable corrosion protection, since VCI products do not actually displace moisture.

Common misconceptions about VCI products displacing moisture

One common misunderstanding is that VCI behaves like a desiccant or moisture displacer, so we are commonly asked, “Do VCI products displace moisture?” It does not. VCI technology prevents corrosion by chemistry, not by drying the environment.

In applications involving high humidity, washed parts, or temperature swings, ZERUST® often recommends combining VCI packaging with proper drying practices and, when needed, desiccants or rust preventative fluids.

Do VCI products displace moisture or require additional moisture control

If parts are packaged while damp, exposed to humid environments, or shipped long distances, additional measures may be necessary. These can include:

  • Improved drying or rinse water control
  • Use of desiccants inside the package
  • Applying compatible rust preventative coatings before VCI packaging

Working with ZERUST® corrosion experts helps ensure the right combination of technologies is used for each application.

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