What is corrosion?
Corrosion is the process that takes place when the essential properties within a given material begin to deteriorate after exposure to the elements of the environment.
Very often this deterioration is visible in metals and we refer to it as oxide. What happens in this case is that chemical reactions arise from an exposure of the metal to the presence of water and oxygen.
In general, corrosion is the oxidation of metals in the presence of water or water vapour and is known as "oxide" (for iron, steel), "white rust" (in galvanized steel) and there are also other terms about corrosion failures such as tarnishing, pitting, flaking and detachment.
Protection against corrosion
To fight against corrosion in packaging, and prevent the emergence of rust, there are two types of protection:
Active or Chemical Protection
It combats corrosion through the modification of physical processes. Among the most important is the creation of a protective atmosphere, VCI (vapour corrosion inhibition).
Passive or Physical Protection
It combats corrosion creating barriers against moisture.
- Plastic packaging together with desiccant clays
- Barrier Packaging (aluminum complexes)
- Vacuum packaging
ANTIOX® VCI anti-corrosion Protection
VCI products offer protection against the corrosion and the emergence of rust in several ways:
Acting as a physical barrier against external dirt and abrasion, as well as a barrier that helps blocking pollutant and corrosive acid gases (such as sulphur dioxide or hydrogen sulphide) from outside the packed material, thereby avoiding contact of these corrosive gases with the steel surfaces to be protected.
Generating a protective atmosphere with the VCI corrosion inhibitor, which condenses around the metal surface and, at the presence of moisture or acids, creates a protective film that prevents from corrosion.
How does ANTIOX® VCI work
Let's put in a closed space a metal piece or machine and an ANTIOX® VCI product, whose protective vapour is generating the protective atmosphere.
The inhibition process begins when the vapour comes into contact with the metal surface and gets condensed forming a thin layer of crystals of one or two molecules-thick.
At the minimum presence of moisture or acids, crystals dissolve and form a protective film over the metal surface that prevents from corrosion.
We will use ANTIOX® VCI paper and films to wrap and pack the goods or over trays as interleaves; cardboard emitters will be dispersed among the pieces that go in bulk.
How to use ANTIOX® VCI products
For an optimal use of the VCI, the first factor to be considered is the type of material or goods on which we make the application. Different aspects condition whether the anticorrosion protection should be higher or not:
Protection levels should be higher in several cases:
- Whenever acting on cast iron and steel with low levels of carbon.
- When we deal with finished products.
- If we manipulate large metal surfaces.
- For long-term storage.
- In anticipation of sudden temperature changes.
- Facing marine environment's inclement weather.
- When there is lack of outer packaging.
Protection levels could be lower...
- In case of coated steels and high alloy steels.
- With semi-finished products.
- When action is taken on a small metal surface.
- For short-term storage.
- If temperature changes are not meant to be.
- For goods into high quality outer packaging.
Packaging advices and suggestions
- The VCI migrate from the plastic or paper and tend to settle over the closest surfaces. For this reason, it is recommended that some VCI material is added every 35-40 cm., so that saturation inside the packaging is achieved in a minimum time before other pollutant factors can cause corrosion.
- It should also be avoided that the metal is in contact with wood or carton, these being hygroscopic materials with a non-neutral PH, they can cause corrosion and/or absorb moisture from the environment.
- The more pieces - the more area to protect.
- Keep in the warehouse for 24 h after packing.
- Avoid packing hot parts (to minimize condensation).
- Reduce direct contact in condensation points.
- Let VCI vapors flow over the metal. Avoid placing barriers between product and the VCI (film, paper), such as separators or plastic trays. At a given time these barriers could be drilled to help the VCI circulate freely.