Surface finish selection guide

Start from the failure you are preventing. Corrosion in a damp or salty environment points to zinc-nickel, e-coat or anodize; wear or galling points to hard anodize, hard chrome, electroless nickel or a PVD film; appearance points to anodize colours, powder coat or plating; conductivity or EMI grounding rules out insulating films such as anodize and powder coat. Then check the substrate: aluminum anodizes, steel plates or phosphates, stainless passivates. The explorer in the surface finish library places every coating on a corrosion-versus-hardness plane — salt-spray hours against Vickers hardness — so the trade-off is visible at once.

The governing specification with its Type and Class (for example ANODIZE PER MIL-A-8625 TYPE II CLASS 2), the colour or gloss, the thickness or thickness class, the surfaces to be coated and the surfaces to be masked (threads, datums, press fits), and whether a hydrogen-embrittlement relief bake or a seal is required. Every finish page ends its specification section with a complete example call-out.

Yes — every deposited or grown layer adds to the envelope. Type II anodize grows about half its thickness outward (5–12 µm per side), hard anodize adds about 25 µm per side at 50 µm total, zinc plating adds its full 5–25 µm, powder coat adds 60–120 µm and PVD films add only 1–5 µm. Tolerances tighter than roughly ±0.025 mm should be specified after finishing, or the finish should be masked from that feature. Each finish page states the build-up per side.

Mechanical finishes and conversion coatings — bead blast, black oxide, chem film, passivation and Type II anodize — carry the lowest lot minimums and add 2–5 working days. Plating and powder coat sit in the middle. PVD, CVD, thermal spray and hard chrome with post-grind are the premium tier because of vacuum time, masking and fixturing. Relative cost is shown as a tier ($–$$$$) on every page; the exact price appears on the instant quote with the part.

Yes. Finishes are applied by qualified partner shops in FabDigit’s network and inspected on receipt — thickness by eddy-current or XRF where the specification calls for it, adhesion and appearance against the drawing. A certificate of conformance naming the specification, Type and Class ships with the parts; coating-thickness reports and salt-spray test reports are available on request when the drawing requires them.

Some nylon print workflows support dyeing, but compatibility depends on the named material, printing route and post-process. Treat dye as a separate finish: state the colour target or approved sample, cosmetic faces and final acceptance condition. Dyeing does not mean every polymer or arbitrary colour is available.

Vapor smoothing modifies the outer surface, so it should not carry a universal dimensional promise. Name the compatible material and route, then validate final dimensions, witness areas and mating features on a representative finished part.

Name the material product and printing route, the required post-process, the datums and the delivered measurement condition. Include orientation when it affects a functional face, and define the acceptance method for critical fits or cosmetic areas.