Electroplating is what makes a zinc alloy button look like gold, nickel or antique silver, and it is also why the same button can flake after three months if the process was rushed. The colour you see is only the top of a stack of layers, each with a specific job. This guide walks through the plating stack from the bottom up, explains why thickness matters more than the name of the finish, and shows you how to spot the typical defects before you accept a delivery.
Why the metal isn't coloured directly
Most metal buttons, snaps and decorative rivets are die cast in zinc alloy (Zamak) or stamped from brass. Zinc is chemically active: put a thin layer of gold or nickel straight onto it and the two metals slowly diffuse into each other, so the surface darkens or develops white spots. A cast surface also contains micro-pores from gas trapped during casting. That is why intermediate layers go between the base metal and the colour, giving adhesion, levelling and a diffusion barrier.
Metal eyelets PE 0002 flat
Metal buttons with a pink finish 6104047 Col 255 – 22 mm handmade
Round metal rivets 10967L08 – 5 mm decorativeThe stack, bottom to top
0. Preparation: tumbling, degreasing, activation
Parts are tumbled in a barrel with abrasive media to remove casting flash, degreased in an alkaline bath and activated in a mild acid. If even a thin film of oil survives this stage, every layer that follows sits on top of it and will come off with it.
1. Copper strike
The first metal layer is a thin copper strike, roughly 1–2 microns, applied under conditions that bond well to zinc. It seals the surface and makes the later baths possible. Brass parts often need a simpler start because brass is less reactive.
2. Levelling copper
For bright finishes a thicker copper layer follows, usually 5–10 microns. Copper fills micro-roughness and gives a mirror-like base. This is exactly the step that budget buttons tend to shorten, which is why they often look slightly dull or wavy.
3. Nickel
Nickel, often 5–10 microns or more, is the hard barrier layer. It stops diffusion between copper and the final colour and adds scratch resistance. For items in direct skin contact, such as jeans buttons or lingerie snaps, nickel-free systems based on bronze alloys or other barriers are used so the part meets the REACH nickel release requirements.
4. Final colour layer
This is what we call the "finish": gold, silver, chrome, black nickel, gunmetal, antique brass. Decorative gold is typically only 0.05–0.2 microns thick, hundreds of times thinner than a human hair. The colour therefore depends entirely on the quality of the layers underneath.
5. Lacquer
Finally the part receives a clear lacquer, sprayed or applied by electrophoresis (e-coat), which protects the colour from oxidation and sweat. Lacquer is also the most common first point of failure: an impact or harsh washing cracks it, and the colour beneath starts to tarnish.
Tip: when a supplier says "gold plated", ask about the whole package (copper, nickel or nickel-free barrier, gold, lacquer) and the thickness of each layer in microns.
How thick is thick enough?
| Layer | Typical thickness | What happens if it's too thin |
|---|---|---|
| Copper strike | 1–2 µm | Poor adhesion, blisters |
| Levelling copper | 5–10 µm | Visible pores, dull "orange peel" surface |
| Nickel / barrier | 5–15 µm | White zinc corrosion, darkening |
| Decorative colour | 0.05–0.5 µm | Fast wear on edges |
| Lacquer | a few µm | Colour oxidation, sweat marks |
These figures are indicative; the right specification depends on the base metal, the shape and the end use. A coat button that is rarely washed can live with a lighter stack, while a workwear snap or a jeans button that goes through industrial laundering needs a heavier one.
Defects: how to recognise them and where they come from
Blistering
Small bubbles that appear straight away or after heat (ironing, tumble drying). The cause is usually gas trapped in casting pores or poor cleaning. Check: heat a few samples to about 150 °C for an hour and look again; blisters rise to the surface.
Peeling
The plating lifts off in flakes, often together with the copper. This is almost always a preparation or strike problem. Test: press strong adhesive tape onto a bent or scratched area and pull it off sharply.
White or grey spots
White powder around the rim or on the back means the zinc underneath is corroding. The nickel is too thin or porous. You will often see it after a few weeks in a damp warehouse.
Edge wear
Colour disappears from the highest points and copper or nickel shows through. That is normal after long use, but if it happens after a handful of washes, the colour layer and lacquer are too thin.
Stains under the lacquer
Cloudy or brownish areas that won't clean off. The lacquer went onto a part that wasn't rinsed properly and trapped salts underneath.
Checking a batch without a lab
- Inspect 20–30 pieces in daylight: is the tone even, are there pores or stains on the back?
- Run the tape test on two or three pieces.
- Wash samples at the garment's care-label temperature together with denim, five cycles.
- Leave two buttons in a closed jar with a damp cloth for a week; white corrosion shows up quickly.
- Compare colour and gloss against the approved golden sample.
Questions to ask your supplier
- What is the layer sequence and the thickness of each layer in microns?
- Does the plating contain nickel, and is there EN 1811 test data for skin-contact items?
- Is there neutral salt spray data (ISO 9227), and how many hours before corrosion?
- Which lacquer is used, and does it survive dry cleaning?
- How is shade controlled from one batch to the next?
A good supplier answers these points specifically. If the answer is just "gold, high quality", ask for samples and test them yourself.
Plating and price
Every extra micron means more time in the bath and more metal. That is why two buttons with the same shape and the "same" colour can carry different prices; the difference sits in the layers you can't see. When comparing quotes, compare specifications, not just photos.
Bul-tex supplies ready-to-ship metal buttons, snap fasteners and eyelets in a range of finishes, including Nickel Free options, and we produce custom hardware for brands. For more on finishes and button choice, browse our button guides. If you need a specific plating for a collection, get in touch.
