1. Why Export Packaging Matters
A coil of steel strip that leaves the Shanghai plant with a clean, oiled surface can arrive at a destination port with rust stains, pitting, or water damage — not because the steel was defective, but because the packaging failed. Marine transit is one of the most corrosive environments a steel product can encounter: salt-laden air, temperature swings that cause condensation inside the container ("container rain"), and voyage times that can stretch from two weeks to over a month. Packaging is the only barrier between the strip and that environment.
The cost of inadequate packaging is not just the value of the rusted strip. It includes the delay while replacement material is sourced, the cost of returning or disposing of the damaged coil, the customer relationship damage, and in some cases the rejection of an entire production batch because the surface quality no longer meets the specification. A few dollars per tonne of packaging material is cheap insurance against those costs.
This guide covers the standard export packaging system used by HS-FINEB and most Chinese steel strip exporters: the six-layer protection structure, the container loading plans, the corrosion risk assessment by destination, and the material specifications. For the broader shipping and logistics picture — including Incoterms, freight booking and documentation — see the shipping and logistics page.
2. The Six-Layer Protection Structure
Every export coil of steel strip from HS-FINEB is wrapped in a six-layer protection system. Each layer addresses a specific corrosion or damage mechanism, and removing any layer weakens the whole system. The table below summarizes the six layers, followed by a detailed description of each.
| Layer | Material | Function | Failure mode if omitted |
|---|---|---|---|
| 1 (innermost) | VCI corrosion-inhibitor paper | Molecular-level corrosion inhibition on steel surface | Rust initiates at surface defects under condensation |
| 2 | Moisture-proof kraft paper | Mechanical protection for VCI layer; additional moisture barrier | VCI paper tears during handling; corrosion inhibitor exposed |
| 3 | Desiccant packets (silica gel or clay) | Absorbs moisture trapped inside the wrap | Condensation forms inside wrap during temperature swings |
| 4 | Polyethylene (PE) film, heat-sealed | Vapor barrier; seals VCI and desiccant inside; blocks external moisture | VCI dissipates; external humidity reaches strip; all inner layers ineffective |
| 5 | Wooden pallet (ISPM 15 HT) or steel pallet | Structural support; forklift access; isolation from container floor | Coil damaged by forklift; contact with container floor moisture; no handling access |
| 6 (outermost) | Steel strapping (banding), 2–4 bands | Secures coil to pallet; prevents shifting and uncoiling in transit | Coil shifts in container; edge damage; uncoiling; safety hazard |
The six-layer system is the standard export specification. For low-risk destinations (short voyage, temperate climate), some exporters may reduce to four layers (VCI paper + PE film + pallet + strapping), but HS-FINEB applies the full six-layer system as standard for all export shipments. For high-risk destinations, additional protection (wooden crate, waterproof outer wrap, extra desiccant) is added on top of the six layers.
2.1 Layer 1: VCI paper inner wrap
The innermost layer is VCI (Volatile Corrosion Inhibitor) paper — kraft paper impregnated with corrosion-inhibiting chemicals that vaporize at room temperature. The vapor condenses on the steel surface and forms a thin, invisible molecular layer that prevents the electrochemical reaction that causes rust. VCI paper is wrapped directly against the strip surface, with the treated side facing the steel. When sealed inside the PE film (layer 4), the VCI chemicals are trapped inside the wrap and provide continuous protection for 6–12 months, depending on temperature and seal integrity.
VCI paper is the most technically sophisticated layer in the system and the one most often misunderstood. It does not work like a coating — it does not physically block moisture. It works by poisoning the corrosion reaction at the molecular level, so even if some moisture reaches the steel surface, the rust reaction cannot start. This is why VCI paper must be in close proximity to the steel (within the sealed wrap) and why the wrap must remain sealed — once opened, the VCI chemicals dissipate into the atmosphere and the protection drops within days.
2.2 Layer 2: Moisture-proof kraft paper
The second layer is a wrap of moisture-proof kraft paper (also called poly-coated kraft or PE-laminated kraft). It serves two functions: it provides mechanical protection for the VCI paper underneath (preventing tears and abrasion during handling and strapping), and it adds a secondary moisture barrier. The kraft paper is wrapped around the coil with overlapping seams, and the edges are folded and taped. This layer also provides a clean, printable surface for coil identification labels (grade, thickness, width, heat number, weight).
2.3 Layer 3: Desiccant
Desiccant packets (typically silica gel or montmorillonite clay) are placed inside the wrap before the PE film is sealed. The desiccant absorbs the moisture that is trapped inside the wrap when it is sealed — moisture from the ambient air at the packaging station, and any residual moisture on the strip surface. Without desiccant, that trapped moisture would condense on the steel surface during temperature swings in transit (the container heats up during the day and cools at night, causing the air inside the wrap to cycle above and below the dew point). The desiccant quantity is specified based on the coil volume and the expected voyage conditions — typically 50–100 grams of desiccant per cubic meter of wrap volume, doubled for high-risk destinations.
2.4 Layer 4: PE film barrier
The fourth layer is a polyethylene (PE) film wrap, heat-sealed at the seams and ends to create a vapor-tight barrier. This is the most critical layer in the system — it seals the VCI paper and desiccant inside the wrap and blocks external moisture from entering. The PE film is typically 0.08–0.15 mm thick (80–150 gauge), with UV stabilizers for outdoor storage. The film is applied by a coil wrapping machine that spirals the film around the coil with 50% overlap, and the ends are folded and heat-sealed. A properly sealed PE film should hold a slight negative pressure (the film pulls tight against the coil) after the desiccant absorbs the trapped air moisture — this is a visual indicator that the seal is intact.
2.5 Layer 5: Pallet base
The wrapped coil is placed on a pallet base for structural support, forklift access, and isolation from the container floor. Two pallet types are used: wooden pallets (the most common) and steel pallets (for heavy coils or repeat-use programs). Wooden pallets must comply with ISPM 15 — the international standard for wood packaging material — which requires either heat treatment (HT) to a minimum core temperature of 56°C for 30 minutes, or methyl bromide fumigation (MB). Treated wood must bear the ISPM 15 mark, which includes the country code (CN for China), the treatment provider registration number, and the treatment method (HT or MB). Plywood and oriented strand board (OSB) pallets are exempt from ISPM 15 because the manufacturing process (high-temperature pressing) kills pests, but they have lower load capacity and are used only for light coils.
The pallet is sized to match the coil dimensions — typically 100–150 mm larger than the coil outer diameter on each side, with a minimum deck board thickness of 25 mm for coils up to 2 tonnes and 35 mm for heavier coils. The pallet stringers (feet) are spaced to allow standard forklift tine entry from both sides, and the pallet top deck may include a wooden cradle or V-block to prevent the coil from rolling.
2.6 Layer 6: Steel strapping
The outermost layer is steel strapping (banding) — 2 to 4 bands of high-tensile steel strap, typically 19–32 mm wide and 0.5–0.9 mm thick, tensioned around the coil and pallet and secured with metal seals or clips. The strapping prevents the coil from shifting on the pallet during transit, prevents the coil from uncoiling if the inner wrap is damaged, and provides a structural connection between the coil and the pallet for forklift handling. The strapping is applied in both the circumferential direction (around the coil OD) and the axial direction (through the coil ID, over the pallet), with a minimum of two bands in each direction for coils over 1 tonne. Sharp edges on the strapping are covered with edge protectors (cardboard or plastic) to prevent the strapping from cutting into the wrap.
3. Container Loading Plans: 20GP and 40HQ
Steel strip is dense — a single coil can weigh 1–5 tonnes, and a full container load is limited by the container's maximum gross weight, not by volume. The loading plan decides how many tonnes fit, how the weight is distributed, and how much volume is utilized. The table below compares the three common loading methods for both 20GP and 40HQ containers.
| Loading method | Container | Typical payload (tonnes) | Volume utilization | Best for |
|---|---|---|---|---|
| Coils on pallets (horizontal) | 20GP | 18 – 20 | 55 – 65% | Standard coils, fast loading |
| 40HQ | 24 – 26 | 60 – 70% | Standard coils, volume not critical | |
| Coils vertical (stood on end) | 20GP | 20 – 22 | 70 – 80% | Max payload, small-diameter coils |
| 40HQ | 26 – 28 | 80 – 85% | Max payload, best volume utilization | |
| Wooden boxes / crates | 20GP | 16 – 19 | 70 – 80% | Small coils, cut-to-length sheets, high-risk destinations |
| 40HQ | 22 – 25 | 75 – 85% | Mixed loads, fragile material, high-risk destinations |
Payload values are typical for steel strip with density 7.85 g/cm³. Actual payload depends on coil dimensions, pallet weight, and the container's maximum gross weight limit (typically 30.48 tonnes for 20GP and 32.5 tonnes for 40HQ, including tare weight). Volume utilization is the percentage of container internal volume occupied by cargo (coils + pallets + packaging). Vertical loading achieves the highest volume utilization because coils stood on end pack more tightly side by side than coils laid flat.
Three loading methods dominate, and each has a clear use case.
Horizontal pallet loading is the standard method — coils laid flat on wooden pallets, strapped down, and loaded into the container with a forklift. It is fast, requires no special equipment, and works for all coil sizes. The downside is volume utilization: flat coils leave gaps between them and above them, so a 40HQ may be only 60–70% full by volume even though it is at maximum weight. For most steel strip shipments, this is acceptable because the weight limit is reached before the volume limit.
Vertical coil loading stands the coils on end (like cans on a shelf), secured to a pallet or a custom rack. This method eliminates the gaps between flat coils and can raise 40HQ volume utilization to 80–85%. It is the preferred method for small-diameter coils (OD ≤ 600 mm) where vertical stacking is stable, and for shipments where every kilogram of payload matters. The downsides are longer loading time (each coil must be lifted and placed vertically), the need for a coil lifter or C-hook, and the risk of coil deformation if the coils are not properly supported. At HS-FINEB, vertical loading is available on request for coils with OD ≤ 800 mm and weight ≤ 2.5 tonnes.
Wooden box / crate loading packs small coils, cut-to-length sheets, or fragile material into wooden crates, which are then stacked in the container. This method provides the highest level of mechanical protection and allows the addition of extra VCI paper and desiccant inside the crate. It is the standard method for high-risk destinations (tropical climate, long voyage) and for material with a critical surface finish (BA surface, polished strip). The downside is lower payload — the wooden crate adds 10–15% to the cargo weight, reducing the net steel payload — and higher packaging cost. For standard carbon steel strip to standard destinations, the six-layer wrap on a pallet is sufficient; wooden crates are reserved for the cases that need them.
4. Marine Corrosion Risk Grading
Not all export destinations present the same corrosion risk. A shipment to Busan (South Korea) on a 3-day voyage in temperate conditions faces far less corrosion risk than a shipment to Lagos (Nigeria) on a 35-day voyage through tropical waters. The packaging specification should match the risk — over-packaging adds cost, under-packaging causes claims. The table below grades corrosion risk by destination climate, voyage length, and season.
| Risk level | Destination climate | Voyage length | Seasonal factor | Example ports | Packaging spec |
|---|---|---|---|---|---|
| Low | Temperate / dry | ≤ 7 days | Any season | Busan, Kobe, Kaohsiung, Singapore | Standard 6-layer |
| Medium | Temperate / humid | 7 – 20 days | Wet season raises risk | Rotterdam, Hamburg, Antwerp, Los Angeles, Vancouver | Standard 6-layer + extra desiccant |
| High | Subtropical / tropical | 20 – 35 days | Monsoon / wet season = high | Jakarta, Manila, Mumbai, Jeddah, Santos | 6-layer + extra VCI + double desiccant + waterproof outer wrap |
| Very high | Tropical / equatorial | > 30 days | Year-round high humidity | Lagos, Abidjan, Douala, Mombasa, Panama | 6-layer + wooden crate + maximum VCI + triple desiccant + waterproof outer wrap |
Risk grading is indicative and based on typical voyage conditions from Shanghai. Actual risk depends on the specific shipping route, the time of year, the container type (dry van vs. ventilated), and whether the container is stowed on deck or below deck. Deck stowage exposes the container to direct sunlight and rain, raising the internal temperature swing and condensation risk. If you have a specific destination and voyage timeline, share it with the supplier at RFQ so the packaging specification can be tailored.
The corrosion mechanism in a shipping container is worth understanding because it explains why the packaging is designed the way it is. A dry van container is a sealed steel box. During the day, solar radiation heats the container interior to 50–60°C, warming the air and the cargo. At night, the container cools to 20–25°C. The air inside the container holds moisture — from the ambient air at loading, from the cargo, and from the packaging materials. When the air cools at night, its moisture-holding capacity drops, and the excess moisture condenses on the coldest surfaces — typically the container ceiling and walls, and the surface of the cargo. This "container rain" drips onto the cargo, and if the cargo wrap is not sealed, the water reaches the steel surface and causes rust. The six-layer packaging system prevents this by sealing the strip in a micro-environment (the PE film wrap) with VCI chemicals and desiccant, isolated from the container's temperature and humidity swings.
5. Packaging Material Specifications
The table below lists the standard specifications for each packaging material used in the six-layer system. These are the specifications HS-FINEB applies; other suppliers may use equivalent materials with slightly different parameters.
| Material | Specification | Typical quantity per coil | Key requirement |
|---|---|---|---|
| VCI paper | 60–80 g/m² kraft, VCI treated both sides, multi-metal inhibitor | 1.5–2.5 m² per m² of coil surface | Valid for ferrous metals; shelf life ≥12 months in sealed bag |
| Moisture-proof kraft paper | 80–100 g/m², PE-laminated one side, water-resistant | Same coverage as VCI layer | Tear strength ≥400 mN; water absorption ≤5% |
| Desiccant | Silica gel (type A) or montmorillonite clay, 50g/100g packets, Tyvek or non-woven wrap | 50–100 g per m³ of wrap volume (doubled for high-risk) | Moisture absorption ≥30% by weight; some packets include color indicator (blue→pink) |
| PE film | LDPE or LLDPE, 0.08–0.15 mm thick, UV-stabilized, transparent or black | Full wrap with 50% overlap, heat-sealed seams | Tensile strength ≥12 MPa; elongation ≥300%; water vapor transmission ≤15 g/m²/24h |
| Wooden pallet | Solid wood, ISPM 15 HT (heat treated), 2-way or 4-way entry, deck boards 25–35 mm | 1 per coil (or shared for small coils) | ISPM 15 mark visible; load capacity ≥ coil weight × 1.5; no bark, no visible pests |
| Steel strapping | High-tensile steel, 19–32 mm wide × 0.5–0.9 mm thick, zinc-coated or painted | 2–4 circumferential + 2 axial bands per coil | Tensile strength ≥700 MPa; seal strength ≥80% of strap breaking load |
| Edge protectors | Cardboard (3-ply) or plastic V-shape, 50–70 mm leg width | 1 per strapping contact point | Compression strength ≥500 N; prevents strap cutting into wrap |
| Labels | Paper or synthetic, 100×150 mm, printed with grade/heat/weight/coil ID | 2 per coil (one on side, one on end) | Water-resistant adhesive; barcode or QR code optional |
Specifications are typical for HS-FINEB export packaging. Equivalent materials from other manufacturers may be used with equivalent or better performance. VCI paper should be stored in its original sealed bag until use — once opened, the VCI chemicals begin to dissipate and the paper should be used within 30 days. Desiccant packets should be stored in sealed containers and inspected for color indicator status before use.
6. Receiving Inspection Checklist
When the container arrives at your facility, a structured receiving inspection catches packaging damage before the strip is unloaded and stored. Perform these checks in order, and photograph any damage before disturbing the cargo.
- Container seal: Verify the container seal number matches the bill of lading and packing list. A broken or mismatched seal indicates the container may have been opened in transit — inspect for cargo damage or theft immediately.
- Container interior: Before unloading, inspect the container interior for water stains, rust, or debris on the floor and walls. Water stains on the ceiling or walls indicate container rain occurred during transit — the cargo wraps should be inspected extra carefully.
- Coil wrap integrity: Inspect each coil's PE film wrap for tears, punctures, or loose seams. A torn wrap means the VCI protection may be compromised — set that coil aside for priority use or re-wrapping.
- Desiccant status: If the desiccant packets include a color indicator (blue silica gel that turns pink when saturated), check the color through the PE film if visible. Fully saturated desiccant indicates the wrap was exposed to excess moisture.
- Pallet and strapping: Verify the wooden pallets bear the ISPM 15 HT or MB mark (required for customs clearance in most countries). Check that steel strapping is tight and no bands are broken or missing.
- Coil shifting: Check that coils have not shifted on their pallets or within the container. Shifted coils indicate the strapping or bracing was inadequate — the coil edges may be damaged.
- Surface check (after opening): When opening the first coil from a shipment, unwrap it fully and inspect the strip surface for rust, water stains, oil degradation, or pressure marks. A clean surface on the first coil is a good indicator for the rest of the shipment, but spot-check at least one coil from every pallet position.
HS-FINEB ships every export order with a packing list that includes coil-by-coil identification (grade, thickness, width, heat number, net weight, gross weight, pallet ID), and a mill test certificate for each heat. If you have questions about a specific shipment's packaging specification or need to request upgraded packaging for a high-risk destination, contact your sales representative at sales@fineblankingmachine.com or WhatsApp 008613062870081 before the order is packed.