1.Why isn't vacuum packaging more widely used?
Extremely high cost: Cold-rolled coils are heavy (typically tens of tons) and enormous in size (up to 2 meters wide and over 1 meter in diameter). Creating vacuum-sealed bags and vacuuming such "steel behemoths" is extremely expensive in terms of technology and materials.
Impractical operation: Vacuum sealing heavy steel coils at ports or factories is extremely difficult, inefficient, and prone to breakage, making it unsuitable for large-scale maritime logistics.
Insufficient necessity: Other mature and reliable packaging methods are sufficient to meet the challenges of maritime transport and achieve the desired protection.
2.What is the standard rust-proof packaging solution for cold-rolled coils shipped by sea?
Inner Protection (Direct Contact with Steel Coil Surface):
Vacuum Phase Inhibitor (VCI): This is the core of modern marine rust prevention. VCI materials continuously and slowly release rust-inhibiting gas molecules, forming a protective layer on the metal surface, effectively preventing rust even in partially sealed packaging. It is typically wrapped around the surface of the steel coil.
Rust-Inhibiting Oil: Applied after rolling or before packaging, as required by contract. Forms a physical oil film that isolates air and moisture.
Middle Physical Barrier:
High-Strength Waterproof/Moisture-Proof Paper: Multiple layers of thickened kraft paper or composite paper provide a strong physical barrier against moisture penetration and mechanical damage.
Plastic Film: Commonly used is multi-layered, densely wrapped polyethylene (PE) stretch film, providing waterproofing, dustproofing, and partial sealing. This is the most practical alternative to a "vacuum" effect, maximizing air rejection through tight wrapping.
Outer Protection and Reinforcement:
Steel Patches/Caps: Steel plates are used to cover the sides (especially the ends) of the steel coils and secured with steel straps to prevent collisions and scratches during lifting and transportation.
High-Strength Steel Straps: Ensure the entire package will not loosen during long-distance sea voyages.
Wooden Brackets/Bases: Facilitate forklift operations and prevent the steel coils from directly contacting potentially wet container or deck floors.
3.What are some special considerations for sea freight packaging?
Container Selection: Prioritize "weatherproof" standard containers. If deck transport is used, the packaging level needs to be further enhanced.
Container Interior Environmental Control:
Desiccant: Sufficient high-efficiency marine container desiccant (such as calcium chloride desiccant) must be suspended inside the container to absorb condensation generated during transit through different climate zones.
Ventilation: While ensuring safety, moderate ventilation may be necessary to prevent moisture buildup inside the container.
Documentation and Inspection: Packaging plans are usually clearly specified in the sales contract and technical agreement. Before loading, both parties (or a third-party inspection agency) will jointly inspect and record the packaging condition.
4.What is the standard procedure for sea freight of cold-rolled coils?
The solution uses a combination of "VCI rust-proof material + waterproof paper + PE stretch film + steel corner protectors/covers + sufficient desiccant". This is the most common and economical solution in international bulk trade.
5.What is vacuum packaging?
It may only be considered for a few special steel grades with extremely stringent rust prevention requirements (such as certain stainless steels and silicon steels) or for very small-sized precision thin strip coils, and requires explicit customer request and additional cost.