How to Protect Metal Cargo from Corrosion During Sea Freight

Why Metal Cargo Corrodes During Sea Freight

Sea freight exposes metal cargo to a corrosive combination of salt air, humidity, and temperature fluctuations. A 20–35 day ocean voyage creates ideal conditions for rust formation on unprotected steel and iron components.

• Relative humidity inside containers can reach 85–95%
• Salt air penetrates standard packaging easily
• Temperature swings cause condensation inside cartons
• Tropical trade lanes (India to Europe, USA) are particularly humid

VCI Packaging: The Primary Defence

VCI (Volatile Corrosion Inhibitor) is the most effective technology for protecting metal parts during sea transit. VCI chemicals slowly vaporise and deposit a protective molecular layer on metal surfaces, blocking the electrochemical reaction that causes rust.

• VCI bags: poly bags with VCI coating for individual parts or small batches
• VCI paper: wrap sheets for components and assemblies
• VCI film: bulk roll wrapping for larger items like frames
• VCI foam: for cushioning precision components while protecting from corrosion
• Protection lasts 12–24 months in sealed packaging

Desiccants: Controlling Moisture Inside Containers

Container desiccants absorb moisture from the container's internal atmosphere, reducing relative humidity and limiting condensation. They complement VCI packaging as a second line of defence.

Full Protection Protocol for Metal Parts

The most effective approach combines multiple protection layers. For bicycle parts and other metal components exported from India, the following protocol is recommended for sea freight.

• Individual parts: wrap in VCI poly bag or VCI paper
• Inner carton: include silica gel sachet per carton
• Outer carton: use moisture-resistant corrugated (minimum 5-ply for sea freight)
• Container: hang Container Dri desiccant bags — 1 unit per 10 CBM
• Seal cartons: moisture-resistant tape on all seams
• Factory stuffing preferred: reduces handling and exposure time

Common Packaging Mistakes That Cause Corrosion

• Using standard poly bags instead of VCI bags
• Insufficient desiccant quantity for cargo volume
• Cardboard that absorbs and releases moisture (not moisture-resistant grade)
• Loading warm cargo into container — creates condensation as it cools
• Opening containers in humid air at destination before drying out
• Mixing dry cargo with freshly washed or damp components

Frequently Asked Questions