A360 vs A380 -When the 3-% Premium Is Justified

A380 is the world's most used die casting alloy -cost-effective, well-characterized, adequate for a broad range of applications. A360 costs 3-% more. The question is when that premium delivers a return.

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Key Differences

Parameter	A360	A380
Copper (Cu)	0.60% max	3.0-4.0%
Silicon (Si)	9.0-10.0%	7.5-8.5%
Tensile strength	317 MPa	317 MPa
Yield strength	172 MPa	159 MPa
Thermal conductivity	113 W/m·K	96 W/m·K
Corrosion resistance (bare)	Significantly better	Good
Anodizing quality	Better than A380	Functional
Machinability	Good	Excellent

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The Copper Effect on Corrosion

A380's 3.0-4.0% copper forms CuAl2intermetallics at grain boundaries. In electrolytes (salt water, fertilizer, road de-icing salt), these precipitates drive galvanic attack at grain boundaries. A380 in direct outdoor exposure shows pitting corrosion within weeks in chloride environments.

A360's 0.60% maximum copper dramatically reduces this mechanism.

Salt spray data (KastMfg production testing, ISO 9227, uncoated):

• A380 without coating: first pitting at 100-200 hours
• A360 without coating: no pitting at 500+ hours

Practical implication: For fully coated indoor parts, this difference is irrelevant. For outdoor parts where coating damage exposes the substrate (scratches during installation, edge exposure), A360 provides meaningful additional protection at the substrate level.

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The Thermal Conductivity Difference -18% More Heat Transfer

113 vs 96 W/m·K is an 18% improvement. For a heat sink housing at 100W heat load, this reduces operating temperature by approximately 2-°C -which may change a marginal design (84°C junction) to a comfortable one (81°C).

See LED streetlight case study for documented 6°C improvement when switching A380 →A360 on a 150W LED streetlight.

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Anodizing Quality

A360's lower copper content and silicon-modified microstructure produce more uniform Type II anodized layers than A380. For programs where anodized appearance quality matters, A360 is the better substrate.

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Decision Guide

Specify A360	A380 is adequate
Outdoor installation, any climate	Indoor, controlled environment
Coastal or marine environment	Fully coated, no substrate exposure
Chemical exposure (agricultural, industrial)	No chemical contact
Thermal conductivity is a design constraint	Thermal requirement easily met
Anodizing appearance quality matters	Functional anodize acceptable

For most indoor industrial applications in controlled environments, A380 is the correct choice. For outdoor, coastal, agricultural, or thermally demanding applications, A360's premium pays for itself.

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Alloy selection: included in every DFM review: yaoqingpu1983@gmail.com | +86 138 1403 4409