Volatile corrosion inhibitors (VCI) are a type of corrosion inhibitor used to protect ferrous materials against corrosion where it is impractical to apply surface treatements. They slowly release compounds within a selaed airspace that actively prevent surface corrosionA typical application is to protect stored tools or parts inside bags, boxes or cuboards, one advantge of VCIs being that if the container is opened and reclosed, levels of inhibitor will recover.