A metal zipper carries discrete metal elements clenched onto a tape bead. It is the chain people mean when they specify a jean fly, a work jacket, or a hardware look on a coat. Coil is quieter and lighter. Moulded plastic (Vislon / POM) is chunkier and colder-weather friendly. Metal is the abrasion and wash story — if the alloy and the plate are named.
TrimGem University teaches metal zippers alongside jeans buttons and rivets because they share a wash, a plate and a nickel conversation. The Guangzhou platform’s accessory range keeps widening; the mill language does not change.
Alloys are the first spec line
Brass wire (typically 65/35 copper-zinc) is the premium apparel tooth: naturally golden, reasonably corrosion-resistant, a little self-lubricating. It is the default for better jeans, leather jackets and any programme that will see industrial laundry. Ask for the Cu/Zn grade, not the word “brass.”
Aluminium wire is lighter and cheaper. Strength is lower than brass at the same gauge. Surface treatments can imitate brass colour. It belongs on lighter jackets, fashion denim and kids’ outerwear where weight and price matter more than a five-year fly.
Zinc alloy (Zamak) teeth are die-cast, not stamped from wire. Geometry can be more complex; corrosion resistance comes from the plate, not the substrate. Cost is the lowest of the three. Sub-grade zinc saves the mill pennies and shows up later as white rust and broken teeth.
Tape is usually polyester for washable garments; nylon tape appears on luggage and heavy outdoor chains. Denier and weave of the tape are part of lateral strength.
Stamping versus casting
Brass and aluminium: wire is rolled, then a high-speed press cuts a Y-shaped tooth and clamps it onto the bead at a fixed pitch. Typical pitches sit around 2.5 mm on #3, 3.0 mm on #5, 4.0 mm on #8. A 0.1 mm pitch error is enough for the slider to mis-mesh.
Zinc: molten alloy is injected onto the tape in a multi-cavity tool. Temperature control is the process. Pitch tolerance in a serious house is on the order of ±0.02 mm.
Element shapes have mill names — single-point (standard, Y, square) and double-point (“corn,” European). The buyer cares that the slider cavity was cut for that tooth, not that the nickname sounds Italian.
Plate, colour and what ruins them
Brass is often polished, brushed, or antiqued. Zinc must be plated. Common stacks: bright nickel, antique brass over nickel, gunmetal / black nickel, and electrophoretic colour coats. Nickel thickness is a corrosion spec (mills talk in micrometres), not a shade.
Post-plate rinse and neutralization matter. Residual chemistry is delayed corrosion. A 24-hour neutral salt spray (ISO 9227) is a reasonable incoming check on metal programmes.
Metal elements also stain for reasons that are not “bad plating”: peroxide bleach forms black CuO on copper alloys; rubber bands leave black CuS; acid or chromium compounds mark the tooth. Do not bundle brass chain with sulphur-cured elastics. Keep aluminium dry; alkali and acid both attack it.
Assembly and inspection
Stops are clamped; the slider is threaded; length is cut (often ±2 mm). Auto-lock sliders use a zinc or alloy body, steel spring and locking pin. Functional gates include open/close cycling (thousands of cycles), lateral pull, slider lock force, and visual under D65. AQL 2.5 / 4.0 (ISO 2859-1) is a common sampling language.
Gauges in apparel are mostly #3, #4, #5; #8 is outerwear and bags. Closed-end, open-end, two-way closed (X/O) and two-way separating are the same geometry families as other zipper types.
Put alloy + gauge + plate + lock type + tape fibre on the PO. “Metal zipper, antique” is a colour conversation, not a fly that will survive a jeans laundry.