Surface finishing: design rules
Coatings and treatments: anodizing, powder coating, plating, passivation, blasting.
Typical tolerance
Coatings add thickness: powder coat about 50–100 µm, anodizing a few to tens of µm, plating about 5–25 µm; allow for it on tight fits.
Files to send
Drawing marking finish type, colour or spec, and masked areas (threads, bores, contact faces).
Common materials
Anodizing: aluminium (and titanium). Powder coat: most metals. Plating: steel, brass, copper. Passivation: stainless.
The rules, with reasons
- Coating thickness. Allow for the thickness the finish adds; mask threads and tight-fit surfaces. Why: Coatings fill threads and make fits too tight.
- Material compatibility. Match finish to material (anodize aluminium, passivate stainless, plate steel). Why: The wrong finish does not bond or protects poorly.
- Colour. Name a standard (RAL, Pantone, MIL-spec) and ask for a sample on critical colour. Why: Colours differ between lots and shops.
- Racking points. Expect small contact marks where the part hangs in the tank or oven. Why: The part must be held somewhere.
- Part size. Check the tank or oven size against your largest dimension. Why: Oversize parts cannot be processed.
Before you ask for a quote
- Finish type and specification
- Colour
- Masked areas
- Part material
- Quantity
- Certificates
Common mistakes
- Ignoring coating thickness on threads
- No colour standard
- Anodizing a part that is not aluminium
Request a quote Find manufacturers
Typical rules of thumb, not a guarantee. The manufacturer's own design guidelines override them: ask for them and check your design against both before ordering.