1.What are the main risks of storing cold-rolled coils during the rainy season?
Condensation Risk: Large temperature differences between day and night can easily cause condensation on the surface of cold-rolled coils and inside the packaging. Even oiling cannot completely prevent moisture intrusion.
Packaging Failure: Moisture-proof paper loses its barrier properties when damp. In high humidity, the corrosion inhibitor in vapor-phase corrosion-preventing paper may be lost or become ineffective.
Edge Corrosion: The oil film on the edges of steel coils is easily eroded and thinned, becoming the initial point of corrosion.
Storage Environment: Poor ventilation, water accumulation on the floor, or roof leaks in the warehouse will significantly accelerate the corrosion process.
2.What packaging reinforcements should be made for storing cold-rolled coils during the rainy season?
Upgrade your rust-preventive oil – During the rainy season, it is recommended to use a moisture-resistant displacement rust-preventive oil, which has a thicker oil film and stronger resistance to water displacement;
Add vapor phase corrosion inhibitor paper – Apply vapor phase corrosion inhibitor paper or place vapor phase corrosion inhibitor powder packets inside the core and end faces of the steel coil, utilizing the evaporation of the corrosion inhibitor to fill the sealed space;
Strengthen outer packaging – Use moisture-proof plastic film (PE or PVC) for full-enclosure wrapping, and add an outer metal protective ring and end face protective plate to prevent direct contact with rainwater;
Sealing inspection – After packaging, check whether the overlaps are sealed, especially the contact area between the bottom of the steel coil and the pallet, to prevent water from seeping in through capillary action.
3.What are the special requirements for the storage environment during the rainy season?
Warehouse Conditions – Indoor warehouses with sealed concrete floors are preferred, ensuring the roof is leak-free and doors and windows can be closed. If a simple shed warehouse is used, storage of finished coils should be suspended during the rainy season.
Ground Moisture Control – Steel coils must be placed on moisture-proof trays or wooden blocks, maintaining a distance of at least 10cm from the ground. A moisture-proof layer can be laid on the warehouse floor, or dry lime can be sprinkled regularly.
Humidity Control – When the relative humidity exceeds 70%, it is recommended to turn on a dehumidifier or air conditioner. If this is not possible, ventilation should be strengthened to avoid excessive temperature differences between the inside and outside of the warehouse, which can lead to condensation.
Stacking Spacing – Maintain appropriate spacing between steel coils to ensure air circulation and avoid dense stacking that can cause localized moisture accumulation.
4.How should stored cold-rolled coils be inspected and maintained during the rainy season?
Packaging Integrity – Check for damage to the plastic film, loose seals, and discoloration of the moisture-proof paper. Repair any damage immediately with waterproof tape or repackage.
Condensation Signs – Observe the inside of the packaging for condensation. If condensation is found, unpack in a dry environment, reapply oil, and replace the moisture-proof material.
End Face Corrosion – Focus on inspecting the ends, edges, and lifting contact points of the steel coils, as these areas are most susceptible to oil film damage. Wipe with a white cloth to check for signs of yellow rust.
Warehouse Condition – After rain, promptly check the warehouse for leaks and water accumulation on the floor. If any problems are found, immediately relocate the steel coils.
5.Does the amount of oil need to be adjusted when storing during the rainy season?
Recommended oil application rate: During the rainy season, increase the oil application rate by 20%–30% compared to the regular season (e.g., from 1.5 g/m² to 2.0 g/m²) to ensure continuous oil film coverage even under condensation conditions.
Uniformity is paramount: While increasing the oil application rate, ensure uniform coating, especially ensuring adequate coverage of easily rusted areas such as edges and welds to avoid localized accumulation or missed areas.
Consider downstream processes: If the cold-rolled coil requires subsequent welding, painting, or annealing, confirm that the increased oil application rate still meets cleaning or evaporation requirements to avoid affecting downstream processes.
Seasonal formulations: Some rust inhibitor suppliers offer "rainy season-specific" formulations, which have stronger anti-emulsification and resistance to damp heat, and can be switched to before the rainy season.