Powder coating is the most common finish on steel and aluminium furniture and lighting, which means it’s also the most commonly misspecified. The range of what it can do is wider than most designers use.
The process
Electrostatically charged dry powder is sprayed onto a grounded metal surface, then cured in an oven at 180–200°C. The result is a hard, even finish that covers in a single pass and is significantly more durable than liquid paint.
The finish families, compared
| Smooth gloss | Smooth matte | Textured (wrinkle / sand) | Metallic | |
|---|---|---|---|---|
| Scratch visibility | High | Low | Very low | Medium |
| Fingerprint visibility | High | Low | Very low | Medium |
| Edge coverage | Good | Good | Excellent | Good |
| Colour range | Full RAL + custom | Full RAL + custom | Limited | Limited |
| Minimum order for custom colour | 25 kg powder | 25 kg powder | 25 kg powder | 25 kg powder |
The edge rule
Where it fights you
Powder coating adds 60–120 microns of thickness uniformly — which matters for close-tolerance fits, threaded fasteners, and mating surfaces. Mask those areas before coating or account for the build-up. Complex internal geometries and deep recesses may show uneven coverage if the spray can’t reach; a second pass or liquid primer in those areas is sometimes necessary. Edges and corners — particularly on thin sheet metal — can show thin spots; design with a minimum 1 mm radius at all edges if coating coverage is critical.
The hanging point is the other quiet constraint: every part hangs from a hook in the oven, and the hook point stays uncoated. Decide where it goes on the drawing, the same way you’d decide a mould split line.
Where it can be pushed
Two-tone finishes are achievable by masking before the first coat, curing, re-masking, and applying the second. Texture powders (wrinkle, sand, and vein effects) hide surface imperfections better than smooth finishes and give a tactile quality that reads well on utilitarian pieces. For pieces where colour accuracy across a production run matters, specify a powder by brand and code, not just RAL — different manufacturers produce RAL colours differently, and batch variation within a single supplier is real.
Cost drivers
- Custom colour MOQ — ~25 kg of powder is the entry ticket for a colour that isn’t on the shelf
- Masking labour — every masked thread and datum face is manual work, per part, per coat
- Two-tone runs — a second colour roughly doubles the process: mask, coat, cure, re-mask, coat, cure
- Pre-treatment — degrease/phosphate or sandblast before coating; skipping it is how coatings fail later
- Part size — oven and booth dimensions set a hard limit; oversize parts mean a different (more expensive) shop
What to put on the drawing
- Powder by manufacturer and product code, plus the RAL reference — and keep a retained sample from the first run
- Gloss level as a number (e.g. 30% / 70%), not “matte” or “satin”
- Film thickness range if any fit is affected, and which surfaces are masked
- Minimum 1 mm radius on all visible edges
- The hanging point location
- Pre-treatment spec — what happens to the metal before the powder touches it