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VAPOR-PHASE INHIBITORS
     
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                                                VAPOR-PHASE INHIBITORS

Vapor-phase corrosion inhibitors (also referred to as volatile corrosion inhibitors (VCIS)) deposit from a vapor phase on the metal surface to be protected.

Therefore, Vapor-phase corrosion inhibitors are protectwe as long as there is suffkient inhibitor in the vapor phase surrounding the metal to maintain a o condensed phase on the surface. The vapor phase acts only as a transport medium from a sourw to the corrosion site.

The vapor-phase corrosion inhibitor should be volatile enough so that all surfaces to be protected are readily reached but not so volatile that it is rapidly depleted through leaks in the containment vessel in which it is used.

Formulations have been developed that protect ferrous and nonferrous metals.

Vapor-phase inhibitors for ferrous metals are volatile arnines, such as the nitrite, carbonate, and benzoate salts of dkyclohexylamine, cyclohexykunine, and hexamethyleneimine and other polar substances. It appears that the organic portion of the molecules only provides volatility.

Inhibitors for nonferrous metals with vapor space enclosures provide some protection, but they are not as effective as inhibitors used with ferrous metals.

Vapor-phase corrosion inhibitors are used to impregnate wrapping paper or are placed loosely inside a closed container. They are widely used for corrosion protection within packaging.
                                                  
reference: MATERIAL DETERIORATION PREVENTION AND CONTROL GUIDE OF ARMY MATERIAL, PARTONE, METALS (MlL HDBK-73S (MR))