PVD or chemical colouring? Specifying coloured stainless steel for architectural metalwork

Two routes to a coloured surface

BSSA's guidance on coloured stainless steel describes chemical colouring as controlled thickening of the existing oxide film. Reflected light produces interference colours without an opaque pigment layer. Its reported film thickness spans approximately 0.02 to 0.36 micrometres. The same guidance gives about 0.3 micrometres as a typical decorative PVD layer thickness. Those values describe different processes and cannot be used to rank their durability by thickness alone.

PVD, or physical vapour deposition, deposits a thin coating in a vacuum environment. Euro Inox's Colouring Stainless Steel explains that the coating material is vaporised and deposited onto the substrate. The decorative ceramic layer remains thin enough for the underlying texture to show through. A polished substrate and a brushed substrate can therefore produce distinctly different architectural surfaces in a similar colour family.

Ask the supplier to name the colouring route, substrate grade and underlying finish separately. A purchase description such as “champagne stainless steel” leaves all three open. It also leaves uncertainty about any clear topcoat, which should be identified as an additional treatment with its own care instructions.

What a flat swatch cannot settle

Chemical interference colour changes with viewing angle. PVD generally offers greater colour stability across viewing angles, although the metal's reflection and surrounding illumination still affect its appearance. BSSA also stresses colour matching between sheets and sourcing from the same mill and batch. These are useful reasons to assess adjacent pieces together instead of approving a single isolated square.

The Hyatt Place hotel example published by Rimex Metals Australia uses its Gold Pagoda ColourTex finish. The photographs show a patterned coloured surface at building scale. This is an example of that manufacturer's finish, not proof of the performance of a different gold coating or a Xinmao assembly.

For an architectural mock-up, position a typical panel beside a return or adjoining panel. Use the proposed illumination and view it from the approach route as well as straight ahead. A reception wall is seen while walking past; a ceiling is seen obliquely from below. Record the viewing conditions that matter to the actual room.

A phone photograph can document the arrangement, but its exposure and white balance make it a poor colour master. Keep labelled physical reference samples. Where numeric colour or gloss tolerances are proposed, agree the measurement method and how it relates to visual approval. No universal colour-difference limit is assumed here.

Decide the fabrication sequence before the finish is ordered

Euro Inox recommends welding before applying the PVD coating and calls for a bend test when coated material will be formed. Its discussion of interference-coloured material also notes that bending can change the colour depth at the bend. These observations make a formed sample more useful than a flat sample for folded architectural parts.

Consider a hypothetical column cover with a visible welded seam. The project team should establish whether the cover is fabricated and finished as a completed component or assembled from prefinished sheets using an approved connection. The finishing specialist must confirm component dimensions, handling and process access. Neither route should be presumed available from a colour chart.

For a screen, include a representative opening and edge in the trial piece. Record which surfaces are visible from each side and what appearance is required at the cut edges. For a folded wall panel, include the actual bend geometry and protective handling method. This is a proposed acceptance exercise, not a prescribed bend radius or proof that every PVD product can tolerate forming.

Put the agreed sequence on the fabrication information: cutting, forming, joining, surface preparation, colouring and final protection. If a later site alteration changes that sequence, refer it back to the responsible fabricator and finisher before work proceeds.

Compare evidence at the level of the supplied product

“Scratch resistant” needs a defined comparison and test. Ask what specimen was tested, which method was used and whether the substrate and finish match the proposed delivery. A result on a flat coupon does not automatically describe an edge, a formed return or an installed panel with a different surface treatment.

The evidence request should follow the application. A protected wall feature and a lift panel that receives repeated contact have different acceptance concerns. If a coating test is supplied, record its method, conditions and result. A salt-spray duration should not be converted into years of service without a defensible relationship to the intended exposure.

The substrate specification remains a separate decision. Colour names do not identify the alloy or demonstrate suitability for a coastal hotel entrance. Ask for material identification and finish identification as separate records, then have the responsible project specialist assess the combination for its exposure.

For a quotation to Xinmao Metal, the useful package is the room application, panel geometry, nominated material, colour references and the proposed approval sample. This gives a fabricator a basis for discussing the visible metalwork and finishing interfaces without implying that a particular test, coating or production capability has already been confirmed.

Accept a colour range and plan for replacement

BSSA notes that scratches in coloured stainless steel are difficult to repair and that heat joining can cause colour changes that are difficult to blend. Euro Inox likewise warns that aggressive damage to a PVD colour can be irreparable. A maintenance plan should therefore define when specialist assessment or component replacement is preferable to local polishing.

Build that decision into the panel layout. Identify a removable piece, how it is released and which adjoining finishes could be disturbed during access. If spare panels are ordered, record their locations and finish batch, and agree their storage protection. Later availability of a similar colour name does not establish an acceptable match to the installed field.

The final finish approval should link the retained samples to the accepted component, fabrication sequence and inspection record. For custom stainless steel ceilings, extend the review to the visible joint and service opening. For screens and wall panels, check both the face and the exposed returns. The order is ready when the chosen colour is defined as something the team can manufacture, inspect and maintain in its intended location.