Why Parcel Boxes Rust — And What We Do About It

Why Parcel Boxes Rust — And What We Do About It

Quick Intro
Parcel boxes are meant to protect your deliveries, not look like they’ve been through a shipwreck. In this article, we explain why outdoor parcel boxes can rust and exactly what we’re doing to stop it.

A Visual Start
Picture this: the delivery guy walks up with your long-awaited package, but as he drops it off—bam—your parcel box looks like it’s auditioning for a role in a post-apocalyptic movie. Rusty, bubbled paint, flaking like pastry. Not a good look.

So, what causes this? And more importantly—how can we fix it?

The Steel Story: Materials, Welding & Coating

Outdoor parcel boxes are typically made from one of three materials:

Cold-rolled steel (CRS)

Galvanized steel

Aluzinc (galvalume) steel

To find out how these materials handle real-world conditions, we performed a 500-hour salt spray test using a 5% NaCl solution. We tested bare materials, powder-coated surfaces, and coated surfaces that were intentionally scratched to simulate damage.

Test Batch 1: Raw Materials, No Coating,the test duration is 72 hours

We tested cold-rolled steel, galvanized steel, and aluzinc without any protective coating.
Result: Every material rusted, especially the cold-rolled steel has corroded and cannot be distinguished.

Test Batch 2: Black Texture Powder Coating

We applied black textured powder coating on the same materials.
Result:

Cold-rolled steel showed serious rusting and heavy blistering.

Galvanized steel had minor surface flaking and small bubbles, but no visible rust.

Aluzinc steel held up best—surface mostly intact with some moderate bubbling, no rust.

Test Batch 3: White Texture Powder Coating + Electrophoresis

This time, we applied electrophoretic coating followed by white textured powder coating. We then scratched the surface to test rust resistance.
Result (Scratched Surface):

Cold-rolled steel: severe rust at the scratch sites.

Galvanized steel: slight rust, small blisters.

Aluzinc: no rust, moderate bubbling only.

Result (Unscratched Surface):

Cold-rolled: rusted.

Galvanized: some peeling, but no rust.

Aluzinc: remained intact.

So Why Do Parcel Boxes Still Rust?
Under normal conditions, galvanized and aluzinc steel resist corrosion quite well. However, when turning them into parcel boxes, we run into a common issue: welding.

To build a durable box, multiple steel sheets must be joined together. Traditional welding causes heat distortion and leaves visible weld points. To smooth things out, these weld points are ground down—but this process damages the protective coating and exposes raw steel to air and moisture.

And that’s where rust starts.

How We’re Fixing It

To minimize corrosion, we've upgraded our process:

• Riveting instead of welding for most connections
• Spot welding only where structural strength is critical
• The introduction of better laser welding equipment strengthens welding and reduces surface grinding caused by the process.
• Minimal grinding to reduce coating damage

Two coating options:

Powder coating only

Electrophoretic coating + powder coating for high-end protection

Final Thoughts

Based on extensive testing, here’s what we’ve learned:

Cold-rolled steel rusts easily, even when coated.

Galvanized steel resists rust unless deeply scratched.

Aluzinc steel performs best, maintaining integrity even after damage.

By switching up our construction methods and improving surface treatments, we're building parcel boxes that stay rust-free, look sharp, and last longer—even when left outside year-round.