Page 26 - MetalForming June 2009

When Packaging,
No Rust
is a Must
Corrosion is the nature of the beast in metalforming. Metallic parts can corrode during processing, storage and transport. For years, corrosion- preventive oils and greases were the solutions. That meant a lot of time, effort and money spent cleaning parts for further processing or upon delivery to the customer.
The advent of volatile corrosion inhibitors (VCIs) in films and packag-
large and small.
BY LOUIS A. KREN, SENIOR EDITOR
ing wraps signaled a clean, dry method of rust protection.
How VCIs Work
Chemicals in the packaging envi- ronment surrounding parts volatilize
to form a protective molecular layer on part surfaces. So what does it mean when these chemicals volatilize? Cor- rosion-inhibitor compounds vaporize from the paper or film packaging, and attract to the charged metallic surface due to their polar orientation. The VCI molecules align on metallic surfaces to a depth of three to five molecules, migrating into recesses on parts. At this point, the corrosion cell—the flow of electrons in the part alloy and the flow of ions in the electrolytic surface layer— cannot establish itself, thus the layer of molecules passivates the charged surface and creates a barrier that pre- vents oxidation. The VCI packaging prevents salt, dirt and other corrosive contaminants from contacting the part surfaces.
Airtight packing is not required for VCIs to work. When the parts are unwrapped from VCI packaging, the protective layer immediately begins to dissipate. No part washing, dipping or other cleaning is necessary.
Military Needs Spurred Technology Growth
VCI technology grew out of mili- tary needs following World War II, according to Martin J. Simpson, presi- dent and CEO of Daubert Cromwell, a
In the battle against oxidation, new-generation
volatile corrosion inhibitors fit the bill for parts
VCI molecules align on metallic surfaces to a depth of three to five molecules, migrating into recesses on parts. The layer of molecules passivates the charged surface and creates a barrier that prevents corrosion-causing materials such as moisture, salt, dirt and oxygen from depositing directly on the parts.
24 METALFORMING / JUNE 2009
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