Zamak 3 vs. Zamak 5 Zinc Alloy: Properties and Strength Comparison
In zinc alloy die casting, Zamak 3 and Zamak 5 are the most widely used commercial alloys. Although both are based on high-purity zinc, minor chemical differences directly impact physical hardness, mechanical strength, and post-casting ductility.
Dinad Industry offers this technical guide to help engineers and procurement managers select the optimal alloy to maximize B2B product ROI.
1. Chemical Composition: The Key Difference
The core Zamak family formula contains approximately 4% Aluminum (Al) and 0.04% Magnesium (Mg) to prevent intergranular corrosion and boost strength. The dividing line between Zamak 3 and Zamak 5 lies in their copper (Cu) content:
- Zamak 3 (Standard Zinc Alloy): No copper added (strictly capped under 0.1%). It is the global standard for zinc die casting, offering excellent dimensional stability and superior ductility.
- Zamak 5 (High-Strength Zinc Alloy): Formulated with approximately 1.0% Copper. This copper addition changes the alloy's microstructure, significantly increasing tensile strength and hardness, but slightly reducing ductility.
2. Mechanical Property Comparison
This table outlines standard physical and mechanical attributes for Zamak 3 and Zamak 5 (per ASTM standards):
| Mechanical Property | Zamak 3 (Standard) | Zamak 5 (High Strength) |
|---|---|---|
| Tensile Strength | 283 MPa (41 ksi) | 328 MPa (47.6 ksi) ── ~15% Higher |
| Yield Strength | 207 MPa (30 ksi) | 228 MPa (33 ksi) ── ~10% Higher |
| Brinell Hardness | 82 HB | 91 HB ── Greater scratch and wear resistance |
| Elongation (Ductility) | 10% ── Ideal for crimping and bending | 7% ── Prone to micro-cracks under severe bending |
| Impact Strength | 48 J (35 ft-lb) | 46 J (34 ft-lb) |
3. Manufacturing Workability and Secondary Operations
- Crimping and Bending (Ductility): Some die-castings require post-casting deformation like crimping, staking, or riveting during assembly. Zamak 3 performs exceptionally here, because its 10% elongation allows metal deformation without cracking. Zamak 5, containing copper, is harder and can fracture under deep bending.
- Corrosion Resistance & Plating: Both alloys offer excellent fluidity and yield identical surface quality for plating (e.g., chrome, nickel, gold). In corrosive, high-moisture environments, the copper in Zamak 5 provides slightly better base atmospheric corrosion resistance than Zamak 3.
4. Engineering Selection Rules
To maximize manufacturing efficiency, Dinad Industry suggests following these guidelines:
Choose Zamak 3 when:
1. The component features flexible clips, rivets, or requires assembly by crimping/bending.
2. Maximum dimensional stability over time is critical, preventing micro-scale creep under constant stress.
3. General instrument housings, decorative hardware, and consumer toys are being produced.
Choose Zamak 5 when:
1. Higher yield strength, hardness, and wear resistance are required (e.g., lock gears, belt buckles, heavy-duty industrial connectors, gearboxes, handles).
2. The part will face harsh outdoor conditions where atmospheric corrosion resistance is valued.
Dinad Industry Co., Ltd. ── Precision Die Casting & Mold Expert
We possess years of experience in mold design and casting production, providing B2B clients with optimization feedback, tooling configurations, and efficient scale manufacturing.