Zinc Alloys
Zinc is the die-casting metal for small, intricate, high-volume parts. It melts at 380–420 °C, so it casts in hot-chamber machines at cycle rates aluminum cannot match, into steel dies that last a million shots, with thinner walls (0.5 mm), sharper corners and tighter as-cast tolerances than any other metal. Cast zinc also plates beautifully — most chrome-plated hardware is Zamak underneath. The trade-offs are density (zinc alloys weigh as much as steel), creep above 100 °C, and a strength ceiling below aluminum's heat-treated grades.
Zinc alloys by group
Zamak (Zn-4Al)4 % Al ± Cu, Mg · Zamak 3, 5, 2, 74210 – 283The hot-chamber die-casting standards: Zamak 3 for most parts (best castability, plating and dimensional stability), Zamak 5 with 1 % Cu for 15 % more strength, Zamak 2 for the hardest and strongest, Zamak 7 for the thinnest walls and best surface.
ZA alloys (Zn-8 to 27 % Al)8 / 12 / 27 % Al + Cu · ZA-8, ZA-12, ZA-273240 – 370Higher-strength and bearing-grade castings: ZA-8 is still hot-chamber and creep-resistant; ZA-12 and ZA-27 are cold-chamber, sand or graphite-mold cast and machine like bronze — bushings, gears, heavy brackets.
Wrought & specialty zincZn-Cu-Ti sheet, slush-casting alloys820 – 190Rolled zinc sheet for roofing, cladding and battery cans; slush and spin-casting alloys for hollow decorative parts and low-volume prototypes.
Choose a zinc alloy for
Door handles, locks, faucets and decorative hardware that will be plated; connector shells, housings and heat sinks for electronics; gears, levers, brackets and pump bodies in volume; toy and model parts; and any casting under a kilogram where fine detail, thin walls, a smooth surface or a long die life outweigh weight. Zamak 3 is the default; Zamak 5 for more strength, ZA-8 for the best strength and creep still castable hot-chamber.
Look elsewhere when
Weight matters (aluminum A380 castings are 40 % lighter), the part runs above 100–120 °C under load (zinc creeps — use aluminum or brass), the part is large (over ~1 kg, aluminum or cold-chamber ZA-27 becomes more economical), or the volume does not justify a die: machined or printed zinc is rare, so prototypes of a zinc casting are usually machined from aluminum or brass, or cast in a rapid soft tool.
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Zinc Alloy by application
- General die-cast hardware and housings
- Zamak 3 unless there is a reason not to — it is the reference alloy for castability, plating and long-term dimensional stability.
- Strength and hardness
- Zamak 5 is the easy upgrade at the same casting process; Zamak 2 and ZA-27 for gears, levers and structural brackets that would otherwise be aluminum.
- Ductility and thin walls
- Lower magnesium and tighter impurity limits give the best fluidity and elongation — connector shells, zippers and parts that are crimped after casting.
- Bearings and machined castings
- ZA alloys replace bronze in bushings and wear plates at lower cost and weight; sand or graphite-mold cast, then machined.
- Sheet, cladding and hollow decorative parts
- Rolled Zn-Cu-Ti weathers to a self-protecting patina on roofs and façades; slush casting makes lamp bases and figurines without a die.
AI suggestions — verify with an engineer before ordering. Estimates are indicative; the quote page prices your exact geometry.
Manufacturing notes
- Die casting
- Hot-chamber for Zamak and ZA-8: 0.5 mm walls, cored holes, cast-in threads, as-cast tolerances of ±0.05 mm on small dimensions and near-zero draft in places aluminum could not manage. Cold-chamber, sand or permanent mold for ZA-12 and ZA-27. Dies outlast aluminum-casting dies several times over.
- CNC machining
- Zinc alloys machine easily — similar to free-cutting brass — with fine finish and low tool wear; ZA-12 / ZA-27 bar and plate are stocked for machined bearings and prototypes. Zamak is rarely machined from stock because its value is in the casting process.
- Plating and finishing
- Zinc die castings are the best plating substrate among cast metals: copper-nickel-chrome (bright or satin), brass and gold color, black nickel, powder coat, paint and e-coat all take well. Chromate or trivalent passivation for bare corrosion protection; zinc should not be anodized.
- Design limits
- Keep sustained service below ~100 °C and design threads and press fits with creep in mind; zinc also becomes brittle below –10 °C in impact. Specify high-purity alloy (SHG zinc) for parts that must hold size for years — intergranular corrosion in old low-purity Zamak is why vintage die castings crumble.
Most-quoted zinc alloy grades
| Grade | Group | Yield, MPa | Tensile, MPa | Density, g/cm³ | Machinability | Weldability | Best for |
|---|---|---|---|---|---|---|---|
| Zamak 3 | Zamak (Zn-4Al) | 221 | 283 | 6.6 | Excellent | Poor | The default zinc die casting |
| Zamak 5 | Zamak (Zn-4Al) | 268 | 328 | 6.6 | Excellent | Poor | Stronger hardware, same process |
| Zamak 2 | Zamak (Zn-4Al) | 283 | 359 | 6.6 | Very good | Poor | Hardest, strongest Zamak |
| ZA-8 | ZA alloys (Zn-8 to 27 % Al) | 290 | 374 | 6.3 | Very good | Poor | Hot-chamber strength and creep resistance |
| ZA-27 | ZA alloys (Zn-8 to 27 % Al) | 370 | 425 | 5 | Very good | Poor | Highest-strength zinc, bearings |
| ZA-12 | ZA alloys (Zn-8 to 27 % Al) | 240 | 310 | 6.03 | Very good | Poor | High-strength ZA casting |
| Zamak 7 | Zamak (Zn-4Al) | 210 | 283 | 6.6 | Very good | Poor | Plating-grade die-cast zinc |
| Zn-Cu-Ti | Wrought & specialty zinc | 120 | 165 | 7.2 | Very good | Fair | Cold-rolled architectural zinc |
Finishes for zinc alloy
All 111 finishes63 of our 111 surface finishes take zinc alloy: 2 recommended outright, 52 with process care, 9 in limited cases. Each finish opens to its datasheet — thickness, hardness, salt-spray hours, spec codes and the zinc alloy-specific notes — and the configurator prices it on the grade you pick.
| Finish | Group | On zinc alloy | Thickness, µm | Hardness, HV | Salt spray, h | Cost |
|---|---|---|---|---|---|---|
| Plasma Electrolytic Oxidation | Anodizing, conversion & passivation | Limited | 10–150 | 700–1,500 | — | $$$$ |
| Copper Plating | Plating & metallizing | With care | 5–30 | 50–250 | — | $$ |
| Decorative Nickel-Chrome Plating | Plating & metallizing | With care | 0.3–1 | 700–1,000 | 96–500 | $$$ |
| Electroless Nickel Plating | Plating & metallizing | With care | 5–75 | 450–1,000 | 100–1,000 | $$$ |
| Cerakote | Paint, powder & polymer coatings | With care | 20–30 | — | 500–1,000 | $$$ |
| Conductive Coating | Paint, powder & polymer coatings | With care | 15–50 | — | — | $$$ |
| Electrophoretic Coating | Paint, powder & polymer coatings | With care | 15–35 | — | 500–1,000 | $$ |
| Degating | Mechanical finishing & post-processing | Yes | 0 | — | — | $ |
| Trimming | Mechanical finishing & post-processing | Yes | 0 | — | — | $ |
| Bead Blasting | Mechanical finishing & post-processing | With care | 0 | — | — | $ |
| Chemical Etching | Marking, decoration & colour | With care | 5–100 | — | — | $$$ |
| Dot Peen Marking | Marking, decoration & colour | With care | 50–500 | — | — | $ |
| Electrochemical Etching | Marking, decoration & colour | With care | 2–25 | — | — | $$ |
50 more finishes accept zinc alloy — see the full material × finish matrix →
Zinc Alloy — frequently asked
Zamak 3 or Zamak 5?
Zamak 3 for about 70 % of zinc castings: it casts best, plates best, holds its dimensions longest and costs the least. Zamak 5 adds 1 % copper for roughly 15 % more strength and hardness and better creep resistance — worth it for levers, gears and parts that are threaded or press-fit, at the cost of slightly lower ductility and long-term dimensional stability.
Zinc or aluminum die casting?
Zinc for small, detailed, high-volume parts that will be plated or need thin walls, sharp detail, tight as-cast tolerance and very long die life; aluminum for larger parts, anything weight-critical, and anything that runs above 100 °C. The crossover is usually around 0.5–1 kg part weight or where a chrome finish is required — chrome on aluminum is far harder to do well.
How strong is die-cast zinc?
Zamak 3 has about 220 MPa yield and 280 MPa tensile as cast — stronger than A380 aluminum die casting and about the same as 6061-T6 aluminum, but at 2.4 × the density. ZA-27 reaches 370 MPa yield. The weakness is creep: under sustained load above ~80 °C zinc slowly deforms, so bolted joints and springs in zinc need conservative design.
Can zinc castings be machined and threaded?
Yes — zinc alloys machine like free-cutting brass, and cast-in or tapped threads both work. Most zinc castings need only light secondary machining (facing, drilling, tapping) because the as-cast tolerances are so tight. ZA-12 and ZA-27 are also stocked as bar and plate for fully machined bearings and prototypes.
Why do old zinc parts crumble?
Intergranular corrosion from lead, tin and cadmium impurities in pre-1960s alloys — "zinc pest". Modern Zamak made from special-high-grade (99.99 %) zinc with tight impurity limits does not do this; ASTM B86 and EN 12844 alloys hold their properties for decades indoors and with a conversion coat or plating outdoors.