ZAMAK 3 vs ZAMAK 5: Which Zinc Die Casting Alloy Should You Choose?

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When designing a zinc die cast component, one of the first decisions is which alloy to use. The two most common options are ZAMAK 3 (ZP3, ZnAl4) and ZAMAK 5 (ZP5, ZnAl4Cu1), both specified under EN 12844 and, at first glance, quite similar. The core difference comes down to one thing: roughly 1% more copper in ZAMAK 5. Yet this single detail changes strength, hardness, ductility, and long-term behavior enough to steer the entire design decision. This guide breaks down the difference between ZAMAK 3 and ZAMAK 5 and which one to choose, with a look at ZP2 and ZP8 for more demanding applications.

What Is Zamak Alloy, and Why Are There So Many Variants (ZP2, ZP3, ZP5, ZP8)

Zamak (or Zamak/ZA alloys) is a family of zinc-based alloys with added aluminum, copper, and magnesium, engineered for hot chamber die casting. Thanks to a low melting point (around 381-390°C) and excellent flowability, zamak allows manufacturers to produce complex geometries, thin walls, and tight tolerances with a fast, cost-effective production cycle.

The European standard EN 12844 specifies four hot-chamber die castable zinc-aluminum alloys, identified by the codes ZP0400 (ZP3), ZP0410 (ZP5), ZP0430 (ZP2), and ZP0810 (ZP8). The source ingots themselves comply with EN 1774. According to zinc.org, ZP3 and ZP5 are by far the most widely used of the four.

This wasn’t always so tidy: before 1998, Europe had numerous overlapping national standards for zinc die casting alloys, later harmonized under EN 12844 and EN 1774. The key variable distinguishing the variants is primarily copper content (and, in the case of ZP8, aluminum content), since copper is what governs strength, hardness, and long-term stability.

ZAMAK 3: Composition, Properties, and EN 12844 Specifications

ZAMAK 3 (EN 12844 code ZP0400, designation ZnAl4, known in North America as Zamak 3 or Alloy 3) is essentially a binary zinc-aluminum alloy. Its composition allows an aluminum content between 3.7% and 4.3%, with copper capped at a maximum of 0.1%. In practice, ZAMAK 3 is the “cleanest” variant in the family: with no meaningful copper addition, it behaves as the baseline reference alloy in many respects.

Its standout properties are excellent long-term dimensional stability, outstanding castability, and high-quality surface finishes. With a tensile strength (Rm) around 280 MPa and hardness of roughly 82 HB, ZAMAK 3 is the most ductile and least hard alloy in the family — a trait that makes it ideal for secondary forming operations.

Geographically, ZAMAK 3 (Alloy 3) is the prevailing standard in North America and Asia, valued for its balance of physical and mechanical properties and its excellent finishing characteristics, well suited to plating, painting, and chrome treatments. Typical applications include components destined for decorative plating and parts requiring crimping or bending.

ZAMAK 5: Composition, Properties, and Differences from ZAMAK 3

ZAMAK 5 (EN 12844 code ZP0410, designation ZnAl4Cu1, known as Zamak 5 or Alloy 5) starts from exactly the same base as ZAMAK 3 — 3.7-4.3% aluminum — but adds copper content between 0.7% and 1.2% (roughly 1%). This single difference is what sets the two alloys apart.

The effects of that 1% copper addition are well documented. According to technical sources, adding copper produces a tensile strength increase of roughly 10% (Rm around 330 MPa), greater hardness (roughly 91 HB), and improved corrosion resistance compared to ZAMAK 3. In practical terms, ZAMAK 5 yields castings that are marginally stronger and harder.

The trade-off is reduced ductility. ZAMAK 5 is less formable than ZAMAK 3, which directly affects secondary operations such as bending, riveting, or crimping. A component that needs to be deformed after casting may struggle with this lower elasticity. Otherwise, ZAMAK 5 is just as easy to plate, finish, and machine as ZAMAK 3.

Geographically, ZAMAK 5 (Alloy 5) is the more common alloy in Europe, where it has historically been the “default” standard for many die casters. Here too, watch the terminology: the European designation ZP5 (EN 12844) corresponds to the North American Alloy 5 and ASTM specifications, but with minor differences in impurity limits.

Comparison Table: ZAMAK 3 vs ZAMAK 5 vs ZP2 vs ZP8 — Composition and Properties

To put the choice in a broader context, it helps to compare all four EN 12844 alloys in a single table. Values are indicative and consistent with EN 12844 / ASTM B86 designations.

Property	ZP3 (ZnAl4)	ZP5 (ZnAl4Cu1)	ZP2 (ZnAl4Cu3)	ZP8 (ZnAl8Cu1)
Aluminum (%)	~4 (3.7-4.3)	~4 (3.7-4.3)	~4 (3.7-4.3)	~8 (8.0-8.8)
Copper (%)	max 0.1	~1 (0.7-1.2)	~3	~1
Tensile Strength Rm (MPa)	~280	~330	~360	~370
Hardness (HB)	~82	~91	~100	~103
Ductility / elongation	Highest	Medium	Lowest	Low
Creep resistance	Lowest	Medium	High	Highest

ZP2 (ZnAl4Cu3) adds roughly 3% copper to the ZP3 base, achieving a strength increase of about 20%: it’s the strongest alloy in the family. Over time it retains strength and hardness better, but becomes more brittle, is more prone to shrinkage, and is less elastic.

ZP8 (ZnAl8Cu1) takes a different approach: instead of relying on copper, it raises aluminum content to 8%, delivering the best creep resistance in the family along with a lower density (~6.3 g/cm³ versus the ~6.6 g/cm³ typical of zamak alloys). It’s worth clarifying that ZP8 under EN 12844 is not equivalent to “Zamak 8” (which doesn’t exist in the US classification system): the North American counterpart belongs to the technically distinct ZA-8 family.

How should you read this table when making a decision? Identify which property matters most for your application: if formability is the priority, look at elongation; if sustained load matters, look at creep resistance; if mechanical strength is the priority, look at Rm and hardness. For a full picture, see the mechanical properties of zamak alloys.

Mechanical Strength, Hardness, and Ductility: Which Alloy Performs Better

Purely in numerical terms, ZAMAK 5 is marginally superior to ZAMAK 3 in strength and hardness: about +10% in Rm, and hardness rising from ~82 to ~91 HB. If the goal is a stiffer, stronger component without changing the production process, ZAMAK 5 is the natural choice.

The trade-off is ductility. ZAMAK 3 remains the better option when the component must undergo secondary forming operations — bending, riveting, crimping — because its greater elasticity reduces the risk of cracking or failure during cold deformation.

The diagram below summarizes the trade-off along a strength-ductility axis:

ZAMAK 3
more ductile → ZAMAK 5
balanced → ZP2
stronger

The extra strength of ZAMAK 5 makes sense when a component operates under significant mechanical loads and doesn’t need to be deformed after casting. Conversely, when a part is essentially decorative or must be assembled by crimping, the extra strength of ZAMAK 5 offers no real benefit, and the loss of formability becomes a genuine drawback.

Creep Behavior and Long-Term Aging

Creep is the slow, permanent deformation of a material under constant load over long periods, even at temperatures well below its melting point. For components that remain under tension for years — springs, mounting brackets, preloaded parts — creep resistance is a critical parameter.

The creep resistance ranking within the zamak family, according to zinc.org, is as follows:

ZP8 > ZP2 > ZP5 > ZP3

There’s a useful rule of thumb: up to roughly 100°C, ZAMAK 5’s creep rates can be estimated from ZAMAK 3’s charts by adding 10°C to the listed temperatures. In other words, ZAMAK 5 behaves approximately like ZAMAK 3, just at temperatures about 10°C higher. That margin can make a real difference in applications operating near the thermal service limit.

It’s worth remembering that all zamak alloys are designed for continuous service temperatures up to roughly 100-120°C: beyond that threshold, creep accelerates noticeably. Another phenomenon to factor in is natural aging: over time, ZP3, ZP5, and ZP8 tend to lose some tensile strength and hardness while elongation increases. ZP2 is a partial exception, retaining strength and hardness better but becoming more brittle. For related thermal considerations, see our deep dive on zamak melting temperature.

Platability and Surface Finishing: What the Alloy Choice Means for Finishing

An often underrated factor is surface finishing. Both ZAMAK 3 and ZAMAK 5 offer excellent platability, but the copper content in ZAMAK 5 can introduce subtle differences in appearance and coating adhesion. In general, both alloys respond well to the main surface treatments: plating, painting, chrome finishing, and passivation.

The crucial technical point for decorative plating on zamak is the deposition sequence. The standard cycle calls for a copper underlayer (copper undercoat, typically 2-5 μm, followed by acid copper) before nickel plating: without this copper layer, nickel would attack the zinc directly, compromising adhesion. This copper-nickel (Cu-Ni) sequence works well on both ZAMAK 3 and ZAMAK 5. The reference standards for decorative Cu/Ni/Cr finishing on zamak are ISO 1456, EN 12540, and ASTM B456; for chromate conversion/passivation, ISO 4520.

The copper content in ZAMAK 5 can slightly affect coating adhesion and cosmetic results: on projects where final appearance is critical (visible components, polished or chrome details), it’s worth validating the finish on the specific alloy chosen. Learn more in our finishing and surface treatments section.

How to Choose the Right Alloy for Your Component: Practical Criteria and Use Cases

Let’s summarize the decision logic in a quick decision tree, based on the component’s top priority:

Let’s look at two concrete use cases.

Case 1 — a decorative plated component assembled by crimping. Picture a visible hardware component that needs chrome plating and is then crimped during assembly. Here, surface finish and crimping ductility are what matter: ZAMAK 3 is the right choice, offering dimensional stability, excellent platability, and the formability needed for crimping.

Case 2 — a structural component that needs extra strength. A mechanical bracket that must handle higher loads, without undergoing post-casting deformation and without requiring new tooling: ZAMAK 5 delivers roughly 10% more strength and greater hardness while keeping the same hot chamber process.

The advantage of working with a specialized die caster is exactly this kind of guidance on the optimal alloy. Micrometal, based in Erbusco (Brescia, Italy) since 1991 — marking 35 years of activity in 2026 — and ISO 9001 certified, operates 11 production units (7 hot chamber die casting machines from Agrati, Italpresse, and Frech, plus 4 robotic cells with Frech DAW 80 machines) with clamping forces from 20 to 90 tons. This setup allows us to die cast all four EN 12844 alloys — ZP3, ZP5, ZP2, and ZP8 — and to guide customers toward the best fit for each specific component.

If you’re evaluating which alloy to use for your project, our technical team can carry out a dedicated assessment based on your mechanical, aesthetic, and operating requirements. Learn how hot chamber die casting works, or request a quote for your zinc die casting project. You can also call us at +39 030 7760830.

Technical review: Marco Sega

Related articles

• Hot Chamber Zinc Die Casting: How the Process Works
• Mechanical Properties of Zamak Alloys in Zinc Die Casting: Technical Guide
• Zamak Melting Temperature in Die Casting: Complete Technical Guide
• Anodizing Zamak: Why It Doesn’t Work and Which Plating Alternatives to Choose

Content produced with the assistance of artificial intelligence systems and subject to technical oversight by our editorial team. Editorial responsibility: Micrometal S.r.l.