Zamak Zinc Alloys
Zamak alloys are zinc with about 4 % aluminum and a trace of magnesium — the eutectic composition that melts at 380–390 °C and fills a steel die in hot-chamber machines faster than any other structural metal. Zamak 3 casts to about 220 MPa yield and 280 MPa tensile with 10 % elongation; adding 1 % copper (Zamak 5) or 3 % (Zamak 2) buys strength and hardness at the expense of ductility and long-term stability. Walls of 0.5 mm, cast-in threads, as-cast tolerances of a few hundredths of a millimetre and the best plating surface of any casting alloy are why most chrome-plated hardware is Zamak underneath.
Popular Zamak grades
Compare in the explorer| Grade | Yield, MPa | Tensile, MPa | Density, g/cm³ | Machinability | Weldability | Best for |
|---|---|---|---|---|---|---|
| Zamak 3 | 221 | 283 | 6.6 | Excellent | Poor | The default zinc die casting; best plating and stability |
| Zamak 5 | 268 | 328 | 6.6 | Excellent | Poor | Levers, gears and bosses needing 15 % more strength |
| Zamak 2 | 283 | 359 | 6.6 | Very good | Poor | Hardest and strongest; small gears and wear surfaces |
| Zamak 7 | 210 | 283 | 6.6 | Very good | Poor | Thinnest walls, smoothest surface, crimped parts |
Choose Zamak for
Door and window hardware, locks and keys, faucet and shower trim, connector shells and RF housings, automotive interior trim and emblems, appliance knobs and handles, zipper pulls, toy and model parts, and any plated or painted casting under about half a kilogram made in the tens of thousands where detail, thin walls and die life matter more than weight.
Look elsewhere when
The part is weight-critical (A380 aluminum is 40 % lighter, AZ91D magnesium 70 %), it carries sustained load above about 100 °C or is a spring (zinc creeps — brass or aluminum), it is larger than about a kilogram (A380 or cold-chamber ZA-27), it must hold a press fit or thread for decades under load (ZA-8 or brass), or the volume does not justify a die — a machined brass or aluminum prototype is the usual stand-in for a Zamak casting.
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Zamak by application
- Plated decorative hardware
- Zamak 3 or Zamak 7 for handles, faucets, emblems and trim that will be copper-nickel-chrome plated — the fine as-cast surface takes bright chrome with minimal polishing.
- Mechanisms, gears and levers
- Zamak 5 for parts that are threaded, press-fitted or carry a working load; Zamak 2 for small gears, pawls and cams where hardness and creep resistance decide wear life.
- Connector shells and housings
- Zamak 3 and Zamak 7 for electrical connector bodies, RF shields and enclosures — cast-in bosses and 0.5 mm walls with EMI shielding that aluminum die castings cannot match at the same wall.
Working with Zamak
- Die casting
- Hot-chamber machines cycle in seconds at a melt temperature of about 420 °C: walls to 0.5 mm, cored holes, cast-in threads, near-zero draft and as-cast tolerances of about ±0.05 mm on small features, with H13 dies lasting a million shots or more because zinc does not erode steel the way aluminum does. Shrinkage allowance is about 0.6 %.
- Machining and secondary work
- Most Zamak castings need only trimming, drilling and tapping; where they are machined they cut like free-machining brass with fine finish and negligible tool wear. Zamak 7 crimps, stakes and bends after casting; Zamak 2 does not.
- Plating and finishing
- The best plating substrate among cast metals: copper strike then nickel-chrome (bright, satin or black), brass and gold tone, e-coat, powder and paint all adhere. Chromate or trivalent passivation gives bare corrosion protection; Zamak is not anodized. Vibratory or mechanical polishing removes the parting line before plating on cosmetic parts.
- Design limits
- Keep sustained service below about 100 °C and design threads and snap fits for creep — Zamak loses about 30 % of its strength at 100 °C — and note that impact toughness falls sharply below 0 °C. Zamak 3 and Zamak 7 shrink about 0.03 % over years as they age; Zamak 2 and Zamak 5 change slightly more, which matters only on precision fits.
Other zinc alloy series
Zamak Zinc Alloys — frequently asked
What is Zamak?
Zamak alloys are zinc with about 4 % aluminum and a trace of magnesium — the eutectic composition that melts at 380–390 °C and fills a steel die in hot-chamber machines faster than any other structural metal. Zamak 3 casts to about 220 MPa yield and 280 MPa tensile with 10 % elongation; adding 1 % copper (Zamak 5) or 3 % (Zamak 2) buys strength and hardness at the expense of ductility and long-term stability. Walls of 0.5 mm, cast-in threads, as-cast tolerances of a few hundredths of a millimetre and the best plating surface of any casting alloy are why most chrome-plated hardware is Zamak underneath.
Which grade of Zamak should I use?
Zamak 3 unless there is a reason not to — it is roughly 70 % of all zinc die castings, the reference alloy for castability, dimensional stability and plating, and the one every die caster quotes first. Zamak 5 when the part is a lever, gear or threaded boss that needs about 15 % more strength and hardness and better creep resistance; it casts and plates the same, with slightly less ductility. Zamak 2 for the hardest and strongest hot-chamber casting (about 360 MPa tensile, 100 HB) and the best creep and wear resistance — small gears, pawls and bearing surfaces — accepting that it loses some ductility and grows a little as it ages. Zamak 7 is Zamak 3 with less magnesium and tighter impurity limits: the best fluidity for walls under 0.5 mm, the smoothest surface and about 13 % elongation for parts that are crimped or staked after casting.
Which grade of Zamak is the strongest?
Zamak 2 has the highest yield strength in the series at 283 MPa; Zamak 5 follows at 268 MPa. Values are for each grade's default condition.
Which grade of Zamak is easiest to machine?
Zamak 3 (machinability excellent, 90/100), then Zamak 5 (85/100).
Is Zamak heat-treatable?
No. These grades are strengthened by cold work and softened by annealing, not by heat treatment; the conditions are listed on each grade page.
Zamak 2 or Zamak 5 for a gear?
Zamak 5 for most gears and levers: about 270 MPa yield, 90 HB, better creep than Zamak 3 and the same casting and plating behaviour, so the die caster changes nothing but the ingot. Zamak 2 is the answer when wear or a high tooth load decides the part — about 360 MPa tensile, 100 HB and the best creep resistance in the family — but its ductility is lower and it ages with a small dimensional change and some loss of impact strength over years, so keep it off snap fits and tight running clearances.
Zamak 3 or Zamak 7?
Same alloy family and strength; Zamak 7 caps magnesium at about 0.01 % and holds tighter impurity limits, which gives it better fluidity for walls under 0.5 mm, a smoother as-cast surface for plating and about 13 % elongation against 10 %. Specify Zamak 7 for thin cosmetic parts and anything that is crimped, staked or bent after casting; specify Zamak 3 for everything else, because it is the alloy every die caster has in the furnace and the reference for dimensional stability and cost.