Problems during transport of steel products are common. The most widespread issue is corrosion damage. Understanding the possible causes, as well as methods of corrosion prevention, is therefore essential.
The most common causes for corrosion damage include:
- Condensation: temperature fluctuations along with elevated humidity and insufficient ventilation can lead to the formation of condensation
- Sea water impact: cargo may be damaged due to leaking hatch covers or other openings
- Rain water impact: wetting may occur due to leaking truck tarpaulin or throw tarps which lie directly on the cargo
- Impact by splash water: this may be the result of damaged trailer floors or container walls and leaking doors
- Contaminants and gas particles in the air, such as SO2, salts and hygroscopic dust
- Hygroscopic packaging materials with a high inherent water content
Being aware of the causes and their effects is the first important step towards preventing corrosion damage. The following methods are recommended for prevention:
- Active protection using anti-corrosive alloys
- Passive protection by separating the metal cargo from the corrosive agents
- Permanent protection by surface-coating or galvanising
- Temporary protection
Most steel products require temporary corrosion protection for transport. The following three methods have proven to be effective in this respect:
Protective Layer: solvent or water-based corrosion protection agents or oil/wax applied to the steel surface.
Barrier Method: a barrier is created using watertight materials such as sealed poly film or aluminium compound foil and a carefully-calculated quantity of desiccant is added. Proper care is to be taken during packaging, particularly to prevent the formation of pools of water in case of external wetting.
VCI-Method: Volatile Corrosion Inhibitor (VCI) material embedded in film, paper or foam material is used which releases the active agent after packaging, thus creating a saturated atmosphere and establishing the corrosion protection. The protective layer evaporates after the packaging is opened.
Properly designed and executed packaging is essential in order to prevent corrosion damage to metal cargo. Furthermore, the means of transport employed is to be examined thoroughly prior to loading the cargo.