Cargo that was perfectly dry when it was loaded can arrive spotted with mould, rust or water damage, even though the container never leaked. The cause is usually condensation, known in the trade as container rain.
What causes it
Air inside the container holds moisture from the cargo, the packaging and the wooden floor. When the container moves from a warm, humid climate to cooler waters, the roof and walls cool faster than the air inside. Moist air meets the cold steel, condenses and drips onto the goods below.
Cargo most at risk
- Metal parts, tools and machinery, which rust
- Paper, cardboard and textiles, which absorb moisture
- Food, leather and wooden furniture, which are prone to mould
- Electronics, which are damaged by moisture in packaging
How to reduce the risk
- Pack goods dry and keep them dry before loading, because wet pallets and damp cartons add moisture
- Use desiccant bags or container desiccant rods, sized to the cargo and the voyage
- Line the walls or cover cargo with moisture-barrier materials where it makes sense
- Use ventilated containers for goods that release moisture, such as some agricultural products
- Choose treated wooden packaging that meets ISPM 15, and let it dry before use
- Avoid unnecessary gaps, which can concentrate condensation on cold surfaces
Insurance and documentation
Condensation damage is not always covered by basic marine cover, so check your policy wording and keep records of the packing method. Photographs of the loaded container help if a claim is needed.
Our packers use moisture control on routes with large temperature changes. Ask for a quote and tell us what you are shipping.