The basics
how corrosion occurs
As is common in nature, metals also strive to reach their lowest energy state. They want to release the energy supplied during metal production. This is the sole reason why metals corrode.
Corrosion is caused, among other things, by electrochemical reactions between a metallic material and its environment. The exact way in which corrosion occurs can vary depending on the specific conditions. In the area of atmospheric corrosion and packaging technology, the presence of water and oxygen is decisive for the corrosion processes.
- Oxygen: Oxygen plays a central role in many corrosion processes, as it takes part in the electrochemical reactions that lead to the oxidation of the metal. With a few exceptions, oxygen is omnipresent. Oxygen regulation is possible in special cases, but is also very expensive.
- Moisture: Water is often a key factor in corrosion, as it forms the electrolyte together with oxygen. The electrolyte wets the metal and enables it to release metal ions and electrons.
- Electrolytes: In addition to water and oxygen, electrolytes can also be acids or bases. The salts they contain can accelerate corrosion by increasing the conductivity of the medium and facilitating electrochemical reactions.
- Material: The composition and structure of the metal can influence its corrosion resistance. Some metals are naturally more resistant to corrosion than others.
Corrosion is generally a natural process and can never be completely avoided. However, various measures can be taken to slow down, control or minimize corrosion.
the causes
Corrosion in packaging
During normal packaging processes, water and oxygen are also packed alongside the package. At a relative humidity of 40 % or more, steel, for example, begins to corrode. Temperature changes alter the relative humidity of the enclosed air inside the packaging. Decreases in temperature always cause an increase in relative humidity up to condensation. The higher the relative humidity in the packaging, the more pronounced the corrosion reactions if there is no corrosion protection.
- VCI corrosion protection: VCI active ingredients are volatile and therefore leave the carrier medium (e.g. VCI film or VCI paper) at room temperature. They saturate the atmosphere inside the closed packaging and coat the metal surfaces. By influencing the electrochemical processes, they actively prevent harmful corrosion reactions and ensure that the packages retain their value.
- Desiccants: Desiccants can be used to reduce the relative humidity to below 40%. Significant corrosion no longer occurs in these areas and the packaged components are protected against corrosion. In addition to the desiccants, a barrier film is also required. The humidity can be monitored with the aid of indicator cards.
- Oils/greases/waxes: The metal surface can be protected against corrosion by applying liquid or highly viscous corrosion inhibitors. Due to their consistency, the corrosion inhibitors keep water and moisture away from the metal surface. They also contain inhibitors that influence the electrochemical reactions.
To prevent corrosion damage to metal components during shipping or storage, it is important to choose the right packaging concept. It happens time and again that components corrode despite corrosion protection packaging. In this case, the cause of the corrosion must be determined in order to avoid further economic damage. Our corrosion protection experts will support you in developing the right packaging concept to prevent corrosion damage in advance.
