The process, briefly
Physical Vapor Deposition (PVD) is a vacuum deposition process: the metal surface is cleaned, placed in a chamber, and a thin film — typically titanium nitride, chromium nitride, or zirconium nitride — is deposited at the atomic level under high heat and vacuum. The result is a coating measured in microns, bonded to the substrate rather than sitting on top of it.
Decision 1 — base finish
The PVD film is transparent enough that the base steel surface reads through. A mirror-polished base gives a deep, reflective colour. A brushed base gives a satin colour with directional texture. A bead-blasted base gives a flat, matte colour. The colour you see is partly the coating, partly the surface it’s on — choose the base before you choose the colour.
Decision 2 — colour
Standard PVD produces gold, rose gold, black, and gunmetal reliably. The iridescent spectrum effect requires controlling the deposition conditions precisely: layer thickness and deposition angle produce light-interference effects that shift across the visible spectrum. This is achievable in production, but it requires a workshop that has dialled it in. Not every PVD shop will quote it correctly.
Decision 3 — form
PVD coats line-of-sight surfaces uniformly. Deep recesses, internal channels, and tight inside corners will show uneven deposition. Design with that in mind — or use it intentionally.
Where it fights you
Surface preparation before coating is unforgiving: any scratch, weld mark, or machining line that isn’t addressed before the coating goes on will be permanent after. The coating is hard and chemically resistant but not infinitely scratch-resistant on large flat horizontal surfaces (table tops under daily use). Fingerprints show clearly on mirror-polished black and gold.
The fixture matters more than most people expect: every part needs a hanging or contact point inside the chamber, and that point will carry a mark. Decide where it goes; don’t let the workshop decide for you.
Where it can be pushed
Multi-layer deposition can produce gradient colour shifts across a surface. Masking before deposition allows two different finishes on the same piece. The same process on aluminium produces lighter, cheaper pieces — at the cost of some structural stiffness.
Cost drivers
- Chamber load — price is per batch, so small parts in volume are cheap, single large parts are not
- Surface preparation — polishing labour before coating usually costs more than the coating itself
- Colour development — standard colours are off-the-shelf; a tuned spectrum effect is a development project
- Rejects — every pre-coat defect becomes a post-coat reject; budget for first-run loss
- Fixture design — custom racks for odd geometries are a one-time but real cost
What to put on the drawing
- Base finish, specified with a physical sample (mirror / brushed with grain direction / bead-blasted with grit)
- Colour against a signed-off coated sample — not a Pantone or RAL reference, the process doesn’t speak that language
- Masked areas, if two finishes share the piece
- The fixture contact point — where the hanging mark is allowed to be
- Surfaces where line-of-sight coverage matters vs. recesses where variation is acceptable
- Use environment: interior or exterior, and what touches it daily