Volatile Corrosion Inhibition - Clark Testing

Volatile Corrosion Inhibition

Volatile Corrosion Inhibitors (VCI) are materials that are widely used to provide temporary corrosion protection for the surfaces of ferrous and non-ferrous metal parts. The VCI chemicals are inserted into coatings, adhesives, plastics, papers, and powders. In an enclosed environment (e.g. a sealed bag), the VCI chemicals vaporize from the parent material and crystallize on the objects inside to form an inert thin film protective coating, otherwise known as passivation.

The thin film protective layer of VCIs works to mitigate corrosion by protecting the metal from oxygen and water present in ambient air.
The thin film protective layer of VCIs works to mitigate corrosion by protecting the metal from oxygen and water present in ambient air.

VCI inhibitors work by:
  • acting as a protective barrier from external dirt and abrasion, and also as a barrier to help block the diffusion of corrosive acid gas pollutants from outside the ICT® packaging material (such as sulfur dioxide or hydrogen sulfide) – thereby preventing contact of these corrosive gases with enclosed metal surfaces.
  • passivating the electron flow between the anodic and cathodic areas on metal surfaces and interrupt the electro-chemical corrosion process.
  • repelling water, which inhibits water from permeating the metal surface and providing the electrolyte for corrosion reactions.
VCI effectiveness depends on a multitude of factors including package integrity and porosity, temperature, humidity, acidity and UV exposure. VCI chemicals are often used in automotive packaging, steel packaging, metal packaging; and military and hobby markets.

VCI Testing

The packaging industry is not required by any government regulation to perform any testing of the VCI infused products. Therefore, there is no regulatory driver of VCI testing. Many manufacturers and end users of VCI materials use single tests for the evaluation of the quality of VCI packaging materials either to tout their own product, or to showcase their product’s superiority to that of a competitor (predatory testing if you will).

The one method garnering the most attention in VCI testing is NACE (National Association of Corrosion Engineers) TM 0208-2013 “Laboratory Test to Evaluate the Vapor Inhibiting Ability of VCI materials for Temporary Protection of Ferrous Metal Surfaces.” This method is easy to perform and is based on U.S. MIL-STD-3010 Test Method 4031. It is also the first in a planned sequence of three standard test methods with other two methods testing non-ferrous corrosion protection and how atmospheric contaminants may affect corrosion protection of VCIs. The latter two methods have yet to be published by NACE.

The strength of NACE TM0208-2013 is that it is published by the world’s corrosion experts and qualifies VCI materials on a scale of 0 to 4.
  1. no corrosion protection
  2. slight corrosion protection
  3. moderate corrosion protection
  4. good corrosion protection
  5. excellent corrosion protection

Major VCI Providers

  • Zerust
  • Branopac
  • RustxUS
  • Armor Protective Packaging
  • Transilwrap (Metpro)
  • Oji F-Tex
  • Protective Packaging Corp
  • Green Packaging
  • CVCI
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