Zamak 3 vs Zamak 5 -The Definitive Comparison

Zamak 3 and Zamak 5 differ by exactly one element: copper. Zamak 3 has >=.10% copper; Zamak 5 has 0.75-1.25%. That single difference produces measurable but focused property changes.

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Composition Difference

Element	Zamak 3	Zamak 5	Impact
Aluminum (Al)	4.0%	4.0%	Same
Copper (Cu)	>=.10%	0.75-1.25%	All property differences
Magnesium (Mg)	0.04%	0.04%	Same
Zinc (Zn)	Balance	Balance	Same

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Properties

Property	Zamak 3	Zamak 5	Preferred
Tensile strength	283 MPa	331 MPa	+17%
Yield strength	200 MPa	228 MPa	+14%
Elongation	10%	7%	-0%
Hardness	82 HRB	91 HRB	+11%
Compressive yield	414 MPa	600 MPa	+45%
Impact strength	58 J	65 J	+12%
Creep resistance	Standard	Better	Measurable
Plating suitability	Excellent	Excellent	Same
Die life	Same	Same	Same
Cost	Baseline	+3-%	Small

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The Trade-Off in Plain Terms

Copper in Zamak 5 buys strength (+17% tensile, +45% compressive yield) at the cost of ductility (-0% elongation). For most applications, this favors Zamak 5 -the strength is valuable, the ductility reduction is inconsequential because zinc hardware is rarely designed to deform plastically in service.

For applications where ductility under assembly forces, snap-fit engagement, or drop impact is important, Zamak 3's higher elongation is the correct choice.

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Creep -The Often-Overlooked Factor

Zinc alloys are susceptible to room-temperature creep (time-dependent deformation under sustained load). Zamak 5's copper reduces creep rate by 30-40% versus Zamak 3. This matters for:

• Parts with press-fit components that must maintain engagement force over years
• Loaded bearing surfaces where dimensional creep affects clearance
• Threaded insert housings where clamping load must be maintained

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Decision Framework

Application	Zamak 3	Zamak 5
Decorative furniture hardware	Yes	Yes
Padlock body (forced entry load)	-	Yes
Snap-fit assembly (ductility)	Yes	-
European architectural hardware	-	Yes(ZnAl4Cu1 is EU default)
Automotive seat hardware	-	Yes
Maximum plating quality	Yes	Yes(same)
Threaded insert housing	-	Yes(creep resistance)
Max volume economy	Yes	-

North America: Zamak 3 is the default. Specify Zamak 5 when structural load, creep, or wear resistance is required.

Europe: Zamak 5 (ZnAl4Cu1 per EN 1774) is the default. Specify Zamak 3 only when maximum elongation or cost savings are the deciding factor.

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