Zamak 5 (Zinc Alloy 5) -The Stronger Zinc Die Casting Alloy

Zamak 5, also designated Alloy 5 (North America), ZnAl4Cu1 (Europe per EN 1774), and ASTM Alloy No. 5, is the second most widely produced zinc die casting alloy globally and the dominant zinc alloy in European die casting. The addition of approximately 1% copper to the Zamak base composition -the only difference from Zamak 3 -delivers a meaningful improvement in mechanical strength and hardness while retaining the same excellent castability, surface finish quality, and decorative plating capability that make the Zamak family the standard for high-volume zinc die casting.

For applications where Zamak 3's strength is sufficient, Zamak 3 is the economically correct choice. For applications where the part is structurally loaded, subject to wear, or requires better resistance to creep deformation under sustained stress, Zamak 5 is the appropriate specification -and is dominant in European automotive and hardware supply chains for exactly these reasons.

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Chemical Composition

Element	Nominal %	Allowable Range	Standard
Aluminum (Al)	4.0	3.9-4.3	ASTM B86
Copper (Cu)	1.0	0.75-1.25	Key addition -differentiates from Zamak 3
Magnesium (Mg)	0.04	0.03-0.06	Grain refiner, reduces inter-granular corrosion
Iron (Fe)	-	0.075 max	-
Lead (Pb)	-	0.005 max	Critical purity limit
Cadmium (Cd)	-	0.004 max	Critical purity limit
Tin (Sn)	-	0.003 max	Critical purity limit
Nickel (Ni)	-	0.001 max	-
Zinc (Zn)	Balance	-	Base metal -minimum 99.99% SHG ingot

Per ASTM B86; EN 1774 ZnAl4Cu1

The copper content of 0.75-1.25% is the defining difference from Zamak 3 (copper maximum 0.10%). The critical impurity limits -Pb >=.005%, Cd >=.004%, Sn >=.003% -are identical to Zamak 3 and equally important. These trace elements cause inter-granular corrosion (zinc pest) in both alloys; KastMfg uses only Special High Grade (SHG) zinc ingot at 99.99% minimum purity to maintain these limits.

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Mechanical Properties

Property	Zamak 5	Zamak 3 (reference)	Improvement
Tensile strength	331 MPa (48,000 psi)	283 MPa	+17%
Yield strength	228 MPa (33,000 psi)	200 MPa	+14%
Elongation	7%	10%	-0% (trade-off)
Hardness	91 HRB	82 HRB	+11%
Shear strength	262 MPa (38,000 psi)	214 MPa	+22%
Compressive yield strength	600 MPa (87,000 psi)	414 MPa	+45%
Impact strength (Charpy, unnotched)	65 J (48 ft·lbf)	58 J	+12%
Fatigue strength (5x10^8 cycles)	56 MPa	48 MPa	+17%
Creep strength (70°C, 10 MPa, 100h)	Lower deflection	Higher deflection	Better

The compressive yield strength improvement (+45%, from 414 to 600 MPa) is particularly significant for applications with press-fit components, threaded inserts, or bearing surfaces.

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Physical Properties

Property	Zamak 5	Zamak 3
Density	6.60 g/cm³	6.60 g/cm³
Melting range	380-386°C	381-387°C
Casting temperature	400-430°C	400-430°C
Thermal conductivity	109 W/m·K	113 W/m·K
Electrical conductivity	25% IACS	27% IACS
Coefficient of thermal expansion	27.4 μm/m·°C	27.4 μm/m·°C
Modulus of elasticity	86 GPa	86 GPa
Poisson's ratio	0.27	0.27

Zamak 5 and Zamak 3 have essentially identical physical properties -density, melting range, casting temperature, and thermal expansion are the same. The mechanical difference is entirely attributable to the copper addition, with no change in physical behavior.

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The Metallurgical Role of Copper in Zamak 5

Understanding why 1% copper produces a 17% increase in tensile strength helps engineers appreciate when the upgrade from Zamak 3 is worthwhile.

Solid Solution Strengthening

Copper dissolves in the zinc-aluminum matrix as a solid solution, replacing zinc atoms in the crystal lattice. These copper substitutions disrupt the regular lattice structure, creating strain fields that impede dislocation movement. Dislocation movement is the atomic mechanism of plastic deformation -impeding it increases the stress required to deform the metal, raising both yield strength and tensile strength.

Precipitation Hardening Contribution

At Zamak 5's copper level (0.75-1.25%), a small fraction of the copper precipitates as CuZn4intermetallic particles during solidification and aging. These fine precipitates further hinder dislocation motion, contributing a precipitation hardening component to the strength improvement.

Creep Resistance

Zinc alloys are susceptible to creep (time-dependent deformation under sustained load) at room temperature -a characteristic that affects the long-term dimensional stability of loaded parts. Copper reduces creep rate in Zamak 5 versus Zamak 3 by approximately 30-40% at typical service stresses. This makes Zamak 5 the preferred choice for:

• Parts with press-fit or interference-fit components that must maintain engagement force over time
• Parts with loaded bearing surfaces where dimensional creep affects clearance
• Parts fastened with threaded inserts where clamping load must be maintained

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Zamak 5 as the European Standard

While Zamak 3 is dominant in North American die casting (accounting for roughly 80% of zinc die casting volume), European die casters default to Zamak 5 / ZnAl4Cu1 as their baseline alloy. The reasons are historical and practical:

European zinc die casting developed with Alloy 5 as the standard from early in the industry's history. European automotive specifications -particularly German OEMs and their tier supplier networks -typically specify ZnAl4Cu1 (the EN designation for Zamak 5) as the standard zinc die casting material in the absence of other specification. European hardware manufacturers, architectural hardware suppliers, and consumer goods producers similarly default to Alloy 5.

For KastMfg customers with European OEM supply chains, Zamak 5 with EN 1774 ZnAl4Cu1 material certification is the standard deliverable. We maintain both ASTM B86 and EN 1774 certification formats.

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Die Casting Process for Zamak 5

Zamak 5 is processed identically to Zamak 3 in hot-chamber die casting:

• Same machine type (hot chamber)
• Same injection parameters
• Same die temperatures (150-220°C)
• Same cycle times (15-25 seconds)
• Same die life expectations (300,000-400,000+ shots on H13 tooling)

From a process perspective, switching between Zamak 3 and Zamak 5 requires only a material change -the die, machine settings, and secondary operations remain identical. This makes alloy substitution during program development straightforward if strength requirements change.

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Applications

Automotive -Structural Zinc Components

Zamak 5's higher strength and hardness make it standard for zinc automotive components that are load-bearing or wear-critical:

Door systems: Lock cylinders, door handles (internal mechanism), window regulator mechanisms, hinge components, striker plates. These components engage repeated loading forces that would cause fatigue or wear issues in Zamak 3 over a 10-year vehicle service life.

Seat hardware: Recliner mechanism housings, adjuster gear covers, latch components. Seat mechanisms are subject to both cyclic loading (daily adjustment) and static loading (occupant weight) -Zamak 5's creep resistance is valuable here.

Engine bay components: Carburetor bodies, fuel system components, sensor housings in the engine bay. Higher temperatures (80-100°C) at the upper limit of Zamak 5's service range but within acceptable bounds for these applications.

Transmission and driveline: Shift lever detent bodies, neutral safety switch housings, small precision brackets in the drivetrain.

Hardware and Building Products

European architectural hardware almost universally specifies Zamak 5:

Security hardware: Padlock bodies, deadbolt housings, mortice lock cases, multi-point lock components. Lock bodies must resist forced-entry loading without fracture -Zamak 5's higher strength provides meaningful resistance to attack.

Door and window hardware: Espagnolette fittings, window fastener bodies, tilt-and-turn hardware mechanisms, balcony door fittings. European building hardware standards (EN 1634, EN 1630) set performance requirements that Zamak 5 meets; Zamak 3 may be marginal.

Architectural fittings: Door and window handles with internal mechanisms, escutcheons, handle roses, hinges for heavy doors. Higher quality architectural hardware specifies Zamak 5 for durability.

Industrial Hardware

Pneumatic fittings: Push-in fitting bodies, quick-connect couplings, manifold bodies for pneumatic systems. The higher compressive yield strength of Zamak 5 maintains the interference fit required for reliable sealing.

Industrial fasteners: Snap fasteners, quarter-turn fasteners, panel fasteners, cam locks. Load-bearing fastener hardware benefits from Zamak 5's compressive strength.

Electrical components: Grounding clamps, conduit fittings, terminal housings with press-fit inserts. Copper content slightly reduces electrical conductivity versus Zamak 3 (25% vs 27% IACS) -negligible for most applications.

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Surface Finishing

Zamak 5 accepts the same decorative and protective finishes as Zamak 3, with equivalent quality:

Finish	Application	Notes
Decorative chrome plating	Automotive trim, bath hardware	Zinc's smooth surface is ideal for chrome
Bright nickel plating	Hardware, fashion accessories	High-quality decorative finish
Satin nickel / brushed nickel	Architectural hardware	Growing preference over chrome
Gold plating	Luxury hardware, fashion	Warm decorative finish
Powder coating	Industrial, outdoor	Color and corrosion protection
Painting	Consumer products	Color flexibility
E-coating	Automotive primers	Corrosion protection before topcoat
Clear lacquer	As-cast metallic appearance	Protects without color change

The copper content in Zamak 5 does not adversely affect plating quality compared to Zamak 3. Both alloys accept decorative electroplating with equivalent adhesion and appearance.

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Long-Term Dimensional Stability

One concern sometimes raised about zinc alloys is post-casting dimensional change -slow shrinkage or growth over weeks and months after casting. This phenomenon, if significant, would affect assembly fit and function for precision components.

In practice, correctly produced Zamak 5 from SHG-grade zinc ingot shows dimensional stability within ±0.001 in/in (±0.025 mm/25 mm) over the typical 2- week period between casting and assembly. The critical factor is impurity control -iron, lead, and cadmium above specification cause accelerated aging changes. KastMfg's spectrometer verification of every melt ensures the alloy purity required for stable castings.

For critical applications requiring maximum dimensional stability, a stabilization anneal (3- hours at 100°C) immediately after casting can eliminate 70-80% of the total aging dimensional change, front-loading the change before machining or assembly.

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Equivalent Designations

Standard	Designation
ASTM B86 (USA)	Alloy 5, No. 5
EN 1774 (Europe)	ZnAl4Cu1 -European baseline alloy
BS 1004 (UK)	Alloy B
JIS H5302 (Japan)	ZDC2
ISO 301	ZnAl4Cu1

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Frequently Asked Questions

Can Zamak 5 be used at elevated temperatures?

Zinc alloys including Zamak 5 begin to lose strength noticeably above 100°C. At 100°C, tensile strength is approximately 70% of room-temperature values; at 120°C, approximately 60%. For applications where operating temperatures routinely exceed 80-90°C, ZA-8 or ZA-12 (higher aluminum zinc alloys) provide better elevated-temperature performance. Most hardware, automotive interior, and consumer applications operate well within Zamak 5's comfortable service range.

Is Zamak 5 better than Zamak 3 for chrome plating?

Both alloys produce equivalent chrome plating quality. Plating adhesion, brightness, and corrosion resistance of the chrome/nickel/copper plating stack depend primarily on surface preparation and plating process control, not on the 1% copper difference between the alloys. If decorative plating quality is the only criterion, either alloy is equally suitable; if the part also carries load, specify Zamak 5.

How does copper affect the corrosion resistance of Zamak 5?

In standard neutral or mildly acidic environments, the 1% copper in Zamak 5 has negligible effect on corrosion resistance compared to Zamak 3. Both alloys require chromate conversion coating or electroplating for outdoor and humid environments. In highly acidic environments, the copper can slightly accelerate selective dissolution; for such applications, Zamak 3 is marginally preferred. In practice, virtually all zinc die castings are surface treated before service, making the bare-metal corrosion comparison academic.

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Zamak 5 die casting inquiry: yaoqingpu1983@gmail.com | +86 138 1403 4409 | No.6, Rungu Road, Nanjing, China