Wuxi Guoyin Metal Material Co., Ltd.

Guide to the complete system of rust-proof packaging for galvanized steel coils shipped by sea

Guide to the complete system of rust-proof packaging for galvanized steel coils shipped by sea

Container loading specifications + galvanized layer protection solution

In cross-border steel trade, the anti-rust packaging of galvanized steel coils directly determines the cargo damage rate. This article analyzes the three core protection systems in international shipping scenarios: design of moisture-proof solutions for shipping, scientific loading specifications for containers, and active protection technology for galvanized layers, to help export companies control the rust rate below 0.3%.

1. Risk analysis of galvanized steel coil corrosion

Risk source Impact on galvanized layer Consequences and cases
Marine salt spray damages the passivation film and causes white rust Zinc crystals appear on the Philippine route in 7 days
Container condensation Condensed water causes electrochemical corrosion When the temperature changes by 30℃, the water accumulation in a single coil exceeds 500mL
Friction damage Local galvanized layer falls off and causes red rust The edge wear rate of unshielded steel coils reaches 8%

2. Quadruple protection system for marine moisture protection (key solutions)

▶ First layer: Vapor phase rust prevention (VCI) sealing

Use 0.15mm thick VCI-ND type rust-proof film to wrap 3 layers

Molecular-level protective film is formed on the surface of the zinc layer (salt spray test > 2000 hours)

Technical points: Relative humidity in the film must be ≤35% (built-in humidity indicator card)

▶ Second layer: dynamic drying system

H-shaped drying rod inserted into the core (moisture absorption ≥ 300g/root)

Container drying bag placed on the top (CaCl₂ type, 40kg/cabinet)

Data support: RH < 45% can be maintained within 40 days of shipping cycle

▶ Third layer: buffer oxygen-isolating packaging

Roll surface covered with puncture-resistant composite paper (weight ≥ 120g/m²)

Nitrogen airbags filled in the gap between steel coils (inflation pressure 0.05MPa)

▶ Fourth layer: container environment control

CTU-PRO nano anti-condensation coating sprayed on the inner wall of the cabinet

Moisture-absorbing pads laid on the floor (water storage capacity 1.5L per square meter)

Actual comparison: rust rate of traditional PE film packaging 5.2% → rust rate of quadruple protection system 0.25%

3. Six major specifications for container loading (ISO 1496-1 standard)

①. Positioning specifications

When loading vertically, the coil diameter direction is parallel to the short side of the container

The coil core hole must be filled with a polyurethane support plug (compressive strength ≥ 8MPa)

②. Fixing specifications

\text{Number of straps} = \left\lceil \frac{\text{Roll weight (t)}}{2} \right\rceil \times 4

Example: 25 tons of steel coils require 12 strips (3 groups × 4-way bundling)

③. Spacer specifications

Rubber anti-slip mats are laid between layers (Shore hardness 70±5)

Wave-shaped corner guards are installed on the edges (thickness ≥ 15mm)

④. Loading taboos

It is forbidden to share the same cabinet with acids/fertilizers (> 3m away from corrosive products)

The environmental temperature monitor must be fixed on the inside of the cabinet door

4. Special protection process for galvanized layer

Different protection is adopted for different galvanized types:

Galvanized type Protection focus Exclusive solution
Hot-dip galvanizing (HDG) Zinc flower crystal protection Spraying water-based acrylic protective wax (film thickness 3μm)
Electrogalvanizing (EG) Anti-fingerprint film maintenance PE+non-woven composite protective film
Zinc-aluminum-magnesium (ZAM) Blocking magnesium element activity VCI vapor phase anti-rust paper full wrapping
⚠️ Special warning: Amine rust inhibitors cannot be used for chromium-passivated galvanized coils (initiating hexavalent chromium conversion)

5. International certification packaging identification system
Graphic logo
https://example.com/packing-symbols
(Must include: moisture-proof umbrella label, lifting position label, no rolling label)

Document system

IMO International Dangerous Goods Packaging Certificate (UN Specification Certification)

Declaration of Conformity (DoC) includes ASTM D3951 standard

Third-party anti-rust test report (according to ISO 9020 standard)

Conclusion
The essence of galvanized steel coil sea transportation packaging is to build a dynamic moisture-proof microenvironment + physical protection system. The VCI sealing technology, container drying system and active galvanizing layer protection solution mentioned in this article can help export companies reduce cargo damage claims by 92% and ensure that each batch of goods is delivered to end customers in perfect condition.