When you open a quotation for a custom workshop trolley, you will see two finishes mentioned repeatedly: powder coating and zinc plating. They are not interchangeable — each protects steel in a different way. Understanding the difference helps you specify correctly and avoid both overpaying and under-protecting.
What Each Finish Does
- Powder coating is a dry polyester or epoxy powder, cured at ~200°C into a tough colored skin. It protects by barrier — keeping moisture and chemicals away from the steel surface. It also provides color, texture and brand identity.
- Zinc plating (electro-galvanizing) deposits a thin zinc layer that protects by sacrifice — zinc corrodes first, shielding the steel even at small scratches. It is metallic, thin and colorless/blue-ish, often with a clear passivate.
When to Use Which
| Part | Recommended Finish | Reason |
|---|---|---|
| Frame, shelves, panels | Powder coating (RAL color) | Appearance, scratch resistance, brand color |
| Bolts, nuts, washers | Zinc plating | Threads need precision; barrier paint breaks threads |
| Drawer slides, small brackets | Zinc plating | Thin profile, dimensional accuracy |
| Outdoor carts | Galvanize + powder (duplex) | Best corrosion life for wet environments |
Quality Checks for Powder Coating
- Film thickness: 60–100 µm; measure with a coating thickness gauge on flat surfaces and near edges.
- Adhesion: cross-cut tape test (ISO 2409) — coating should not peel.
- Salt spray: request ISO 9227 results (e.g. 240–500 h without red rust) for outdoor use.
- Pre-treatment: degreasing and zinc phosphate conversion coating before powder make the finish stick — skipping this causes early flaking.
Bottom Line for OEM Buyers
Specify powder coating for visible structural parts (with a specific RAL and gloss level) and zinc plating for hardware and small precision parts. For coastal or outdoor applications, upgrade to a duplex system. Fulei Metal runs both lines in-house, so we can apply the right finish to every part of your trolley under one roof — ask us for process photos and test reports.