Aluminum vs Zinc Die Casting -Choosing the Right Material for Your Part

Aluminum and zinc are the two dominant die casting metals globally, together accounting for over 90% of all die casting volume by weight. Both produce complex, net-shape components at high volume with excellent dimensional repeatability. But they differ significantly in density, minimum wall thickness, die life, surface quality, plating suitability, and cost profile -and choosing the wrong one early in the design stage creates problems that are expensive to fix later.

This guide compares aluminum and zinc across every parameter that matters to engineers and buyers, and provides a clear decision framework.

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Property Comparison

Property	Aluminum A380	Zinc Zamak 5
Density (g/cm³)	2.74	6.60
Weight vs aluminum	-(baseline)	2.4x heavier
Tensile strength (MPa)	317	331
Yield strength (MPa)	159	228
Elongation (%)	3.5	7
Hardness	80 HRB	91 HRB
Thermal conductivity (W/m·K)	96	113
Electrical conductivity	Good	Good
Melting temperature (°C)	590-650	380-390
Minimum wall thickness (mm)	1.2 mm standard	0.4 mm standard
Dimensional tolerance	CT4-CT6	CT3-CT5 (tighter)
As-cast surface finish	Ra 1.6-2.2 μm	Ra 0.8-1.6 μm (smoother)
Electroplating suitability	Limited (requires prep)	Excellent -preferred substrate
Die life (cold/hot chamber)	80,000-150,000 shots	300,000-1,000,000+ shots
Cycle time	30-120 seconds	15-25 seconds
Max service temperature	~175°C	~100°C
Corrosion resistance (bare)	Good	Moderate

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Understanding the Key Differences

Weight and Density

Zinc is 2.4 times denser than aluminum. For a part of identical geometry, a zinc casting weighs 2.4x more than the equivalent aluminum casting. This single factor often drives the decision for automotive, aerospace, portable electronics, and any weight-sensitive application. If your design spec includes a maximum part weight, aluminum is almost always the answer.

However, density is not everything. Zinc's superior casting fluidity allows thinner walls, which can reduce part weight more than the density difference suggests. A zinc part with 0.5 mm walls may weigh less than an aluminum part with 1.5 mm walls -even though zinc is denser.

Minimum Wall Thickness

This is zinc's clearest advantage. Zinc die casting reliably achieves 0.4 mm walls; aluminum's practical minimum is 1.2 mm. For small precision components, connectors, and complex thin-section parts, zinc enables geometries that are simply not achievable in aluminum.

Surface Finish and Plating

Zinc produces a smoother as-cast surface (Ra 0.8-1.6 μm vs aluminum's Ra 1.6-2.2 μm) and is the preferred substrate for decorative electroplating. Chrome plating, nickel plating, and gold plating all adhere excellently to properly prepared zinc castings with minimal pre-plating work. Aluminum can be plated, but requires more extensive pre-treatment and produces less consistent results for decorative applications.

Dimensional Tolerance

Zinc achieves CT3-CT5 as standard; aluminum achieves CT4-CT6. In practical terms, zinc die casting parts typically require less post-cast machining for dimensional features -reducing secondary operation cost and supply chain complexity.

Die Life and Economics at High Volume

Zinc's low casting temperature (385-390°C) is far less thermally aggressive on H13 tool steel than aluminum's 650°C. The result: zinc dies routinely outlive equivalent aluminum dies by 3-x. Over a multi-million-piece program, this dramatically reduces total tooling amortization cost per unit -often making zinc cheaper per part despite higher material density.

Strength-to-Weight Ratio

Despite zinc's higher absolute tensile strength, aluminum wins decisively on strength-to-weight ratio. A380 aluminum (317 MPa at 2.74 g/cm³) has a specific strength of 116 MPa·cm³/g. Zamak 5 (331 MPa at 6.60 g/cm³) has a specific strength of 50 MPa·cm³/g. For structural applications where strength per unit mass matters, aluminum is the correct choice.

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Decision Framework

Choose Aluminum When:

• Weight is a constraint -automotive lightweighting, portable devices, EV range optimization
• Operating temperature exceeds 100°C -zinc softens above ~100°C; aluminum is stable to ~175°C
• Thermal conductivity is important -heat sinks, motor housings, thermal management components
• Part is large -aluminum's low density makes large castings (>1 kg) far more economical than zinc
• Corrosion resistance in bare condition is needed -aluminum's native oxide layer provides good protection without coating
• Alloy upgrade options are needed -T5/T6 heat treatment can significantly improve aluminum mechanical properties

Choose Zinc When:

• Decorative plating is required -chrome, nickel, or gold plating on zinc is the industry standard
• Walls are thinner than 1.2 mm -zinc is the only die casting metal that reliably fills 0.4-0.8 mm walls
• Maximum dimensional precision on small parts -CT3-CT5 as-cast, minimal machining required
• Very high volume with long die-life economics -zinc die life of 500,000-1,000,000 shots dramatically reduces tooling cost per unit
• Part size is small-to-medium -zinc's density disadvantage matters less for small parts
• Weight is not a constraint -hardware, locks, automotive trim, consumer products

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Real-World Examples

Part	Material Choice	Reason
Automotive door handle	Zinc (Zamak 5)	Decorative chrome plating, complex geometry, moderate structural load
EV motor housing	Aluminum (A380)	Weight, thermal management, size (>3 kg)
Padlock body	Zinc (Zamak 3)	Decorative finish, thin walls, high volume economics
LED streetlight housing	Aluminum (A360)	Heat dissipation, large size, outdoor corrosion resistance
Connector housing	Zinc (Zamak 3)	Thin walls, dimensional precision, high volume
Hydraulic manifold	Aluminum (A413)	Pressure tightness, machinability, temperature resistance

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Frequently Asked Questions

Can the same part be made in both aluminum and zinc?

Geometrically similar parts can be made in either alloy if the wall thickness is achievable in both (>=.2 mm). The tooling and process would be different (cold chamber for aluminum, hot chamber for zinc), and the part weight and cost would differ significantly. KastMfg regularly provides parallel quotations in both alloys for customers deciding between them.

Which is cheaper -aluminum or zinc die casting?

Neither is universally cheaper. At low volumes, aluminum tooling is similar in cost to zinc tooling. At very high volumes (1 million+ parts), zinc's longer die life makes it more economical per unit despite the higher material cost per kg. For small parts (under 100 g), zinc's faster cycle time and longer die life often result in lower unit cost.

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