Zamak 3 and Zamak 5 are two of the most common zinc alloys used for custom die-cast hardware. Both can produce detailed shapes with good surface finish, but they are not identical. For global OEM buyers, the right choice depends on strength, ductility, finishing, part geometry and cost target.
Zamak 3 and Zamak 5 differ mainly in copper content — Zamak 5 has ~1 % copper while Zamak 3 has <0.1 %. Zamak 3 is the default for decorative hardware (handles, knobs, covers) because it casts and plates more consistently. Zamak 5 is chosen when mechanical strength or wear resistance matters more — load-bearing brackets, fittings, repeatedly tightened parts. Both can be polished and plated equally well when casting porosity is controlled. For your RFQ, specify load conditions, target salt-spray hours, and which dimensions are critical after plating.
Quick answer
Zamak 3 is the default choice for many decorative and general-purpose zinc die-cast parts because it casts well and offers stable dimensions. Zamak 5 contains more copper, which improves strength and hardness but slightly reduces ductility. It is often chosen when the part needs better mechanical strength or wear resistance.
| Item | Zamak 3 | Zamak 5 |
|---|---|---|
| Common use | Decorative hardware, handles, knobs, housings | Stronger hardware, brackets, fittings, functional parts |
| Castability | Excellent | Very good |
| Strength | Good | Higher |
| Ductility | Better | Slightly lower |
| Surface finishing | Excellent for polishing and plating | Excellent when casting and polishing are controlled |
Typical property values (as-cast)
| Property | Zamak 3 | Zamak 5 |
|---|---|---|
| Aluminium content | ~3.5–4.3 % | ~3.5–4.3 % |
| Copper content | ≤ 0.1 % (typ.) | 0.75–1.25 % |
| Tensile strength | ~283 MPa | ~328 MPa |
| Elongation | ~10 % | ~7 % |
| Hardness (Brinell) | ~82 HB | ~91 HB |
(Typical as-cast values in line with ASTM B86 / EN 12844. Actual properties vary with foundry practice and batch — request the material certificate for your production lot rather than designing to catalogue numbers.)
When Zamak 3 is usually the better choice
Zamak 3 is widely used because it has a strong balance of castability, dimensional stability and finishing quality. It is often the best first option for furniture handles, cabinet knobs, decorative covers, door hardware and parts where the appearance is more important than heavy mechanical load.
- Thin decorative shapes with fine detail
- Parts requiring bright chrome, gold, antique brass or black nickel finishes
- High-volume hardware where stable molding and finishing yield matter
- Components with moderate load and no severe impact
When Zamak 5 is worth considering
Zamak 5 is often selected when the part needs improved hardness or mechanical strength. The added copper can make it better for fittings, brackets, lock components and functional hardware that sees higher stress. However, the design still needs proper radii, wall thickness and gate planning to avoid casting defects.
Buyer note
If the part is decorative and lightly loaded, Zamak 3 is often enough. If the part is load-bearing, repeatedly tightened, or exposed to friction, ask the supplier whether Zamak 5 or another process is safer.
When Zamak 5 is not worth it
If the part is purely decorative — a handle, knob or cover that is gripped but never load-bearing — Zamak 5 buys strength you will never use. Zamak 3 fills thin decorative sections slightly better, holds dimensions across long runs, and gives marginally more consistent plating yield. In that situation the “stronger” alloy is simply the wrong specification, not an upgrade.
Which alloy is cheaper?
Ingot prices are close; Zamak 5 carries a small premium for its copper content, and Zamak 3’s easier casting tends to give slightly higher first-pass yield. For most hardware projects the total difference is minor compared with tooling, plating and packaging costs — so choose the grade by mechanical requirement first, not by the ingot price.
Finishing considerations
Both grades can be polished and plated well when the casting surface is clean and low-porosity. The finish quality depends less on the grade name alone and more on die design, melt control, polishing sequence and plating stack. For premium hardware, specify the finish sample, plating layer requirement and salt-spray target in the RFQ.
Questions to send with your RFQ
- Is the part mainly decorative, functional or both?
- What load, torque or repeated movement will it see?
- Which surface finish and salt-spray requirement are needed?
- Which dimensions are critical after plating?
- Is the order for sampling, batch production or long-term supply?
Key takeaways
- Zamak 3 is the common default for decorative zinc alloy hardware.
- Zamak 5 is useful when higher strength or hardness is required.
- Surface finish depends on casting quality, polishing and plating control.
- The best grade choice should be tied to the part drawing and application.
Frequently Asked Questions
What's the main difference between Zamak 3 and Zamak 5?
Zamak 5 contains more copper (~1 %) than Zamak 3 (<0.1 %). The extra copper increases strength and hardness but slightly reduces ductility. Zamak 3 is the default for decorative hardware where casting and finishing matter most; Zamak 5 is chosen when mechanical strength or wear resistance is more important.
When should I choose Zamak 5 over Zamak 3?
Choose Zamak 5 for parts that are load-bearing, repeatedly tightened, or exposed to friction — brackets, fittings, lock mechanism components. For decorative furniture handles, knobs, and covers with light mechanical load, Zamak 3 is typically the better choice because it casts and plates more consistently.
Do both Zamak grades plate equally well?
Both can be polished and plated well when casting porosity is controlled and the pre-treatment sequence is correct. Zamak 5's slightly different copper content can affect plating bath behaviour, but in practice the finishing line setup matters more than the grade choice for the final visual result.
What information should I send with a Zamak RFQ?
At minimum: is the part decorative, functional, or both; load, torque, or repeated movement the part will see; target surface finish and salt-spray hours; critical dimensions after plating; and whether this is for sampling, batch production, or long-term supply. This lets the supplier propose the right grade and process.
Is Zamak 5 more expensive than Zamak 3?
Slightly. Zamak 5 carries a small ingot premium for its copper content, and Zamak 3's easier casting usually gives marginally higher production yield. For most hardware projects the total cost difference is small compared with tooling and finishing costs — specify the grade by mechanical requirement, not price.
Can I switch between Zamak 3 and Zamak 5 in the same mold?
Usually yes. Both alloys run in the same hot-chamber tooling with very similar shrinkage, so an existing mold can normally cast either grade. Plan a short sample run to re-verify critical dimensions and plating pre-treatment before committing a production batch to the new grade.
Not sure which Zamak grade fits your part?
Share the application, drawing and finish target. LuminaCast can recommend Zamak 3, Zamak 5 or an alternate process based on function and appearance.
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