Apparel hardware is small, seen and often next to skin. The alloy decides whether a piece casts a sharp logo, whether it rusts in a salt-spray cabinet, and whether nickel release becomes a REACH problem.
The usual five
Zinc alloy (Zamak / zinc-aluminium, often #3, ZZnAl4Cu1) is the die-casting workhorse. It fills thin walls, takes electroplate well and keeps tool life high because the melt is relatively cool compared with aluminium. Strength is modest. It is the right metal for decorative logos, many zipper pulls and fashion sew-ons that are more jewellery than fastener. Impurities (lead, tin, cadmium) must be controlled; they drive intergranular corrosion.
Brass (copper-zinc) stamps, machines and plates cleanly. Jeans buttons, better eyelets, and engraved sew-ons still use it when the brand will pay. It oxidises; the finish (nickel, antique, clear coat) is the real product.
Carbon steel / iron is cheap and strong. It rusts. Eyelets, rivets and some prong snaps are steel under a copper+nickel+chrome stack. The plate is the corrosion system.
Aluminium is light. It anodises rather than taking a classic copper-nickel-chrome stack the same way. Fine for some pulls and lightweight eyelets; easy to crush if the wall is too thin.
Stainless steel (304 is the apparel default; 316 for harsher wear) is the honest answer for corrosion and for a lower nickel-release risk when the surface is well finished. It is harder to decorate. Use it when the hardware is functional, not when you need a candy-coloured PVD story at a fashion price.
Matching alloy to part
- Sew-on fashion buttons, logos, scarf hardware: zinc die-cast or brass.
- Snaps, jeans buttons, rivets: brass or steel, specified by the fastening system, not by the face colour.
- Eyelets / grommets: brass or steel, with a washer on true grommets.
- Skin-contact fashion jewellery trims: watch nickel release (EN 1811) regardless of how pretty the antique brass looks.
“Gold” is a colour, usually a plated or PVD finish, not 18-karat gold. Put the substrate + finish on the BOM: “Zamak 3, antique brass plate, clear lacquer” is a spec. “Gold metal” is not.