Metal zippers are chosen for how they look and how they last, but the metal itself is only half the decision: plating, lacquer and slider matching decide whether the finish survives the first wash. These six answers cover gauge, corrosion and repair.
Metal Zipper FAQ
Metal or nylon zipper: which should I choose?
Choose metal when the zipper is part of the design and the garment is heavy: jeans, denim jackets, leather, workwear and structured bags. Metal teeth are stronger in compression, hold a crisp line and age visibly, which is often the point. Choose nylon coil when the garment is lightweight, stretchy or washed often, because coil flexes, weighs less and does not corrode. A #5 metal chain is roughly 20-40% heavier than a #5 coil over the same length, which matters on a lightweight jacket. Metal also has to be protected from chlorine and salt, while POM coil tolerates both. The decision rule: if the seam takes tension and the fabric is stable, metal; if the fabric moves or the garment is laundered hard, coil.
What sizes do metal zippers come in and where are they used?
Sizes run #3 to #10. #3 suits trouser flies, pockets and light jackets; #4.5 and #5 are the denim standards, with #5 also used on leather jackets and mid-weight outerwear; #8 covers heavy workwear, coats and boot applications; #10 is for luggage, protective gear and heavy bags. The size number approximates the closed chain width in millimetres, so a #5 measures about 5 mm across the teeth, which is a quick way to check a replacement slider. Gauge should follow load and fabric weight, not fashion: a #3 on 14 oz denim will fail at the fly, and a #8 on a lightweight shirt will look heavy and feel cold. Match the tape width to the seam allowance as well, since metal tapes are usually wider.
Brass, aluminium or nickel-plated: what lasts?
Brass is the most durable for garments: it resists repeated washing, takes plating and lacquer well, and does not pit in mild detergent. Aluminium is light but corrodes in alkaline wash baths and chlorine, leaving grey marks on fabric, so keep it for dry-clean-only or decorative uses. Nickel plating is hard and bright but can release nickel against skin, and it chips at the slider mouth where the chain rubs. For denim, brass with a wash-resistant lacquer is the safe choice; for fashion bags, nickel on brass gives a brighter finish with better wear than nickel on steel. Ask for the substrate, not just the finish name, and test 3-5 washes at the customer's recipe before approving. Salt spray results of 24-72 hours separate a decorative plating from a durable one.
How do I specify a nickel-free metal zipper?
Start with the substrate: specify brass or stainless steel rather than nickel-plated steel, and ask for the alloy grade in writing. If a bright finish is needed, use a coating that acts as a barrier, such as a lacquer or a tin-cobalt deposit, and confirm that the coating covers the slider mouth and the pull, which are the contact points. For skin contact, the relevant limit is 0.5 micrograms per square centimetre per week under the European nickel release method, so a nickel-free label without a test method is not enough. Re-test after any plating or lacquer change, and test the finished slider rather than the raw wire. Keep the report linked to the specific part number and size, because a #5 result does not cover a #3.
Why does the finish discolour or tarnish after washing?
Lacquer is usually the first thing to fail. Detergent pH, chlorine in the water and the tumbling action all attack a thin coating, and once it breaks the brass oxidises and leaves marks on light fabric. Use a lacquer specified for the wash recipe, cure it properly, and avoid abrasive stone wash on lacquered parts. Chlorine is the worst offender, because a single bleach wash can strip a decorative finish. If the garment is garment-dyed, check that the dye bath pH is compatible with the coating, and rinse thoroughly. Test with the actual detergent at the actual temperature for five cycles, then inspect the slider mouth and the top stop, where coating wears fastest. A finish that survives only hand washing should not be specified for a machine-wash garment.
Can metal zippers be shortened or repaired?
Yes, with the right tools. To shorten, remove teeth from the cut end with side cutters, file the wire ends flush, and crimp a new stop 2-3 mm from the last tooth; never cut through a tooth, which leaves a burr that jams the slider. Shorten from the bottom on trousers and from the top on jackets, keeping the original slider park intact where possible. To repair a split, replace the slider first: measure the closed chain, match the gauge, remove the top stop and thread the new slider. If teeth are missing in the middle of the chain, the zipper has to be replaced, because a gap will always reopen. For leather goods, a curved needle and two locking stitches at each end prevent the tape from pulling out. Keep a small stock of sliders in the gauges you use most, since a slider swap is the cheapest repair in the workshop.
YCC and Donglong produce brass, nickel-free and lacquered metal zippers for denim, leather and workwear, with sliders matched to each chain batch.