text: For steel, the first step will be the volatilization of the inhibitor into the airspace. This may entail simple evolution of the molecule or the chemical may dissociate first and then volatilize. The molecules will then diffuse through the enclosed airspace until some of the molecules reach the metallic surface to be protected. There are two likely paths once the molecules reach the metallic surface. First the molecule may adsorb onto the metal surface thereby forming a barrier to aggressive ions and displacing any condensed water.
  The second path involves the condensed water layer that has been shown to exist on the metallic surface. The VCI molecules will dissolve into the condensed water layer, raising the pH. An alkaline pH has been shown to have a beneficial effect on the corrosion resistance for steel.
  The mechanism for copper begins the same as for steel, evolution of the inhibitor. Once at the copper surface however, the inhibitor will form a copper benzotriazole complex which is protective.
  Vapor pressure is critical parameter in VCI effectiveness. The most favorable range of pressure is 10 to 10 Pa at room temperature. Insufficient pressure leads to the slow establishment of the protective layer; if the pressure is too high, VCI effectiveness is limited to a short time.