To prevent edge damage and white rust during a long sea shipment, PPGI coil should be packed as a sealed, moisture-managed unit: the coil wrapped in VCI paper against the steel surface, covered with waterproof VCI film, fitted with edge protectors, secured to a wooden pallet or saddle with steel strapping through the eye or around the circumference, and shipped in a container with desiccants and a documented stowage plan. Orientation, wrapping sequence, strapping method and container humidity control all matter, and the right combination depends on coil weight, transit time, route climate and the terms of your contract.
This article explains the practical options. Treat it as general industry guidance for discussion with your supplier. Your purchase order, packing specification and any referenced standard are what actually govern the shipment, and you should confirm the required edition and exact contract values before production starts.
Why Sea Freight Is Hostile to Prepainted Coil
A prepainted galvanized coil is a layered product: steel substrate, metallic coating, conversion or pretreatment layer, primer and topcoat. Each layer can fail in transit for a different reason.
- Mechanical damage: coil edges are the most exposed surface. Impacts during lifting, stacking or rail transfer can deform edges, crack paint and expose bare steel.
- Moisture and condensation: a container crossing climate zones can cycle through dramatic temperature changes. Warm humid air inside a cooling steel container condenses on cold metal — a phenomenon often called container rain.
- White rust: zinc surfaces exposed to moisture and limited airflow can form white zinc corrosion products. Cut edges, scratches and unpassivated areas are the usual starting points.
- Chlorides: salt-laden air near ports or on deck-adjacent stowage accelerates corrosion once the wrap is breached.
- Pressure and abrasion: stacked coils moving slightly against each other can abrade wrap and paint, especially at the eye and the outer wrap.
Good packaging does not make the coil invulnerable. It buys time and creates a controlled microclimate. The goal is to keep the coil dry, supported and mechanically isolated from the first mile to the last.
Eye-to-Sky vs Eye-to-Wall Orientation
Orientation describes how the coil’s axis — the eye — is positioned in the container or on the pallet. It changes load paths, lifting method and how water can pool or drain.
Eye-to-sky (vertical, eye up)
The coil stands on its side, axis vertical. The wide faces are horizontal and the eye is open to the sky.
- Lifting is usually easier with a C-hook or by slings through the eye, depending on weight and equipment.
- Water can collect in the eye if the top is not covered, so the eye must be sealed and capped.
- The bottom edge carries the full weight, so a flat, strong pallet or saddle and edge protection are essential.
- Stacking is limited by the stability of the base and the risk of edge crushing.
Eye-to-wall (horizontal, eye sideways)
The coil lies on its outer surface, axis horizontal. This is common for heavier coils and for coils that will be uncoiled on arrival.
- The coil rests on a curved surface, so it needs a cradle, saddle or well-formed pallet to stop rolling.
- Weight is distributed along the outer wrap, which can mark or abrade the surface if the wrap is thin.
- Stacking is generally more stable when coils are aligned and chocked, but the outer wrap of the bottom coil bears load.
- Drainage is better because water does not sit in the eye, provided the wrap is intact.
How to choose
There is no universal best orientation. Decide based on coil weight and diameter, lifting equipment at both ends, container internal dimensions, whether the coil will be uncoiled directly, and the stowage plan. Then write the choice into the packing specification, including whether mixed orientations are allowed. If you also buy unpainted galvanized material, the same logic applies to GI coil, though surface sensitivity differs.
Wrapping Sequence: VCI Paper, Film and the Microclimate
The wrap is the coil’s first defense. A typical export build-up, from the steel outward, looks like this:
- VCI paper or VCI film against the steel. Volatile corrosion inhibitor releases vapor that forms a protective layer on metal surfaces, including hard-to-reach edges. It works best in a reasonably sealed space.
- Waterproof barrier film. A polyethylene or laminated VCI film keeps liquid water and humid air out. Seams should be overlapped and taped or heat-sealed.
- Edge protectors. Plastic, board or steel edge rings shield the coil edges from strapping pressure and impact.
- Outer wrap or board. A final layer, sometimes with a hardboard or steel outer cover, resists abrasion and handling damage.
- Strapping. Steel strapping holds the package together; it should sit over edge protectors, not directly on painted surfaces.
Two details are frequently missed. First, VCI needs a reasonably closed environment; a loose, open wrap lets the vapor escape. Second, the coil should be dry when wrapped. Wrapping a damp coil traps moisture against the surface, which is worse than leaving it exposed in a dry environment.
Eye, face and edge protection
The eye should be capped or plugged to stop water and dust entering. The inner and outer edges need protection because they are the hardest areas to coat after damage. The outer wrap should be continuous, with the seam positioned where it will not collect water.
Strapping, Pallets and Handling Hardware
Packaging hardware has to survive lifting, stacking and vibration without crushing the coil or cutting the wrap.
| Element | Typical options | What it protects | Points to confirm in the contract |
|---|---|---|---|
| Orientation | Eye-to-sky or eye-to-wall | Load path, drainage, lifting method | Required orientation, mixed loads, stacking height |
| VCI layer | VCI paper or VCI film | Steel and cut edges against humidity | Type, coverage, whether VCI is required at all |
| Water barrier | PE or laminated film, sealed seams | Liquid water, spray, humid air | Thickness, sealing method, overlap |
| Edge protection | Plastic, board or steel edge rings | Coil edges and paint | Material, coverage, whether required on both edges |
| Strapping | Steel strapping, circumferential and/or through eye | Package integrity | Number and position of bands, tension, seal type |
| Pallet or saddle | Wooden pallet, cradle, skid | Base support, forklift handling | Timber treatment, load rating, saddle fit |
| Desiccants | Container desiccant bags | Condensation inside container | Quantity, placement, whether required |
| Marking | Labels, stencils, tags | Identification and traceability | Coil ID, heat number, weight, handling symbols |
Wooden pallets and skids are often subject to phytosanitary rules in the destination country. Confirm whether heat treatment or another approved measure is required, and ask for the marking that demonstrates it. Requirements vary by market and change over time, so verify against the destination’s current rules rather than assuming.
Container Desiccants and Humidity Control
Desiccants absorb water vapor inside the container and reduce the chance of condensation forming on cold steel. They are most useful on long routes with large temperature swings, and they are not a substitute for a sealed coil wrap.
- Desiccant capacity should be matched to container volume, cargo mass, transit duration and route climate.
- Placement matters: bags are commonly hung along container walls or placed where air circulates, not buried under cargo.
- Container condition matters too. A container with a damaged roof, wet floor or residual moisture can defeat the best packaging.
- Ventilation choices interact with desiccants. Discuss with your freight partner whether vents should be open or closed for your route.
Ask your supplier and forwarder to state, in writing, what humidity-control measures are included and who is responsible for them. Responsibilities often split between the mill, the consolidator and the shipping line, and gaps between them are where claims come from.
RFQ and Packing Specification Checklist
Use this list when requesting quotations or confirming an order. Specific numbers should come from your contract, not from a generic guide.
- Coil dimensions, weight, inner and outer diameter, and quantity per container.
- Required orientation and whether stacking is permitted.
- Wrap build-up: VCI type, barrier film, edge protection, outer cover.
- Strapping pattern, number of bands, material and tension requirements.
- Pallet or saddle type, dimensions, load rating and timber treatment.
- Container desiccant type, quantity and placement.
- Marking and labeling: coil ID, grade, weight, heat number, handling symbols.
- Photographic records of packing before container closing, if you want evidence.
- Inspection or witness points, if any, and who attends.
- Applicable standard, its edition, and the exact values the contract requires.
- Unloading equipment expected at destination, so the packing suits it.
- Handling and storage instructions to pass to the receiving warehouse.
If your project involves both painted and unpainted material, it is worth aligning packing specifications across PPGI coil and GI coil so your receiving team works to one standard.
Common Mistakes That Cause Claims
- Wrapping a wet or warm coil. Trapped moisture becomes white rust before the container even sails.
- Relying on VCI alone. VCI works in a closed space; an open or torn wrap reduces its effect.
- Strapping directly onto painted surfaces. Without edge protectors, bands cut into the wrap and paint.
- Ignoring the eye. An uncapped eye collects water and debris.
- Assuming all containers are dry. Container condition should be checked and recorded.
- No photographic record. Without packing photos, damage disputes become difficult to resolve.
- Copying another buyer’s specification. Transit time, route and climate differ; so should the packing.
- Treating packaging as a formality. It is a technical specification, and it belongs in the contract.
Frequently Asked Questions
Does VCI paper prevent white rust completely?
No. VCI reduces corrosion risk when the package is reasonably sealed and the coil is dry at packing. White rust can still form if moisture enters, if the wrap is damaged, or if the coil was already damp. It is one control among several, not a guarantee.
Is eye-to-sky or eye-to-wall better for long sea transit?
Both are used. Eye-to-wall generally drains better and suits heavier coils; eye-to-sky can simplify lifting but needs a sealed, capped eye and a strong base. The right choice depends on weight, equipment, stowage and whether the coil will be uncoiled directly. Confirm it in the packing specification.
How many desiccant bags should a container have?
There is no single correct number. It depends on container size, cargo mass, transit duration, route climate and the type of desiccant. Ask your supplier or forwarder to propose a quantity based on your route, and record it in the shipping documents.
Do wooden pallets need treatment for export?
Many destinations require approved phytosanitary treatment and visible marking for solid wood packaging. Rules differ by country and are updated periodically. Confirm the current requirement for your destination and ask for evidence of compliance.
What standards apply to coil packaging?
Various national, regional and customer standards may apply, and they can differ in scope and detail. Confirm which standard and which edition your contract references, and verify the exact values required. Do not assume a standard cited in a general guide matches your order.
Will packaging affect the price?
Yes. Cost drivers include wrap materials, VCI type, edge protection, strapping, pallet type and treatment, desiccant quantity, labor and any inspection or photography requirements. Because material and freight costs move, ask for a dated quotation that states the packing scope and validity period rather than relying on an undated figure.
Getting the Specification Right
Packaging for sea freight is a risk-management decision. The strongest practical approach is to define the coil, the route and the receiving conditions first, then specify orientation, wrap, edge protection, strapping, pallets and desiccants to match. Keep records, agree responsibilities in writing, and confirm the standard edition and contract values that apply.
If you are preparing an enquiry, include coil dimensions and weights, destination port, expected transit time, required orientation, and any packing standard your customer requires. Our team can review your requirements against available packing options and confirm what can be quoted. Send your details through our contact page and request a dated quotation with the packing scope clearly stated.
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