How Do You Hold Color Match ΔE 1 on Plated Bezels?

ΔE 1 holds when the ring, the chip and the colorimeter are fixed before plating starts: one layer stack, one customer chip, one reading position. The number is a color difference, not a colour name, and it is read on the coated ring at the post-machining stage rather than judged on a screen.

A Zamak 5 ring cast to ASTM B86 AC41A can carry the same three layers as the previous lot and still read differently, because colour on a plated surface comes from the top layer and the layers under it.

What makes two plated bezels read as different colors?

Chrome thickness does. The top layer is 0.1–0.3 µm of chrome over 10–15 µm of nickel and 8–12 µm of copper, and the visible colour sits in that thin top layer.

Where the chrome runs thin, the nickel underneath shows through and the ring reads slightly warm; where it runs thick, the ring reads cooler and darker. Both rings can be inside the 18–27 µm total and still sit at opposite ends of the colour band.

Surface finish adds a second shift. A ring polished to a different roughness scatters light differently, and the colorimeter reads that as a colour difference even when the coating is identical.

How is ΔE 1 measured against a customer chip?

With a colorimeter, against the chip, at a stated light and a stated position on the ring. ΔE is the distance between two colours in a uniform colour space, and 1 is roughly the point where a trained eye starts to see a difference.

The chip is the reference, not a photograph. A screen or a printed photo carries its own colour cast, and a ring approved against a photo is approved against the photographer.

The reading belongs on the first article with the chip number, the instrument and the spot on the ring. A ring measured at the flat face and a ring measured at the radius are two different readings, and the drawing should say which one counts.

Why does chrome thickness drift across a plating rack?

Because current density is not uniform over a rack. Parts at the edge of the rack and parts at the centre see different current, and chrome, being the thinnest layer, shows the difference first.

Geometry adds to it. A ring has an inside and an outside, and the inside faces the rack while the outside faces the tank; the two faces plate at different rates even on the same part.

Control is rack design and part orientation rather than a longer bath. More time plates everything thicker, including the places that were already at the ceiling, and the spread stays.

What has to be redone when the color changes?

First article, chip and trial fit. A new colour means a new top-layer target, and the press fit that was signed on the previous stack has to be checked again on the new one.

The layer stack can move with the colour. A warmer tone may need a different nickel thickness, and that changes the total, which changes the bore and the interference fit.

That is why a colour change is quoted as a new first article rather than a colour swap. The ring geometry is unchanged, but the coated dimensions are not.

What color acceptance belongs on the drawing?

The chip number, ΔE ≤1, the measuring spot, the light source, and the layer stack that produces the colour. Five items turn a subjective argument into a reading.

The layer stack belongs on the drawing because it is the colour recipe. Copper 8–12, nickel 10–15 and chrome 0.1–0.3 µm are thickness ranges, and the colour sits in how those three are balanced rather than in the chrome alone.

Finally, the stage. If ΔE is read after plating, the drawing should say so; a reading taken on a bare ring predicts nothing about the coated one. Send the chip with the four callouts, and the colour can be quoted against a number.

The same stack also carries the press fit, so a colour change reopens the fit question; that check is handled on the pre-plate bore and the trial case rather than on the colour chip.