A360 Aluminum Alloy -Superior Corrosion Resistance and Thermal Conductivity

A360 is a hypoeutectic aluminum-silicon-magnesium alloy containing approximately 9.5% silicon and 0.5% magnesium, with deliberately low copper content (0.6% maximum). This low-copper, magnesium-modified composition is the defining characteristic of A360 and the source of its two principal advantages over A380: significantly better corrosion resistance and meaningfully higher thermal conductivity.

Where A380 is the correct choice for general-purpose engineering, A360 is specified when the service environment is aggressive (marine, outdoor, humid industrial) or when heat dissipation is a primary function (heat sinks, motor housings, thermal management assemblies).

---

Chemical Composition

Element	Min %	Max %	Role
Silicon (Si)	9.0	10.0	Fluidity, reduces shrinkage
Magnesium (Mg)	0.40	0.60	Corrosion resistance, strength
Iron (Fe)	-	1.3	Reduces die soldering
Copper (Cu)	-	0.60	Kept low -key to corrosion performance
Zinc (Zn)	-	0.50	-
Manganese (Mn)	-	0.35	-
Nickel (Ni)	-	0.50	-
Tin (Sn)	-	0.15	-
Aluminum (Al)	Balance	-	Base metal

Per ASTM B85. The copper limit of 0.60% max (vs 3.0-4.0% in A380) is the critical compositional difference.

---

Mechanical Properties (As-Cast HPDC)

Property	A360	A380 (reference)
Tensile strength	317 MPa (46,000 psi)	317 MPa
Yield strength	172 MPa (25,000 psi)	159 MPa
Elongation	3.5%	3.5%
Hardness	75 HRB	80 HRB
Shear strength	180 MPa	190 MPa

A360 has slightly higher yield strength than A380 (172 vs 159 MPa) due to the magnesium content contributing precipitation hardening in the as-cast condition. Tensile strength and elongation are essentially equivalent.

---

Physical Properties

Property	A360	A380
Density	2.63 g/cm³	2.71 g/cm³
Thermal conductivity	113 W/m·K	96 W/m·K
Electrical conductivity	31% IACS	27% IACS
Coefficient of thermal expansion	21.0 μm/m·°C	21.1 μm/m·°C
Melting range	557-596°C	540-595°C
Casting temperature	630-690°C	620-680°C
Modulus of elasticity	71 GPa	71 GPa

---

Why A360 Outperforms A380 in Two Critical Areas

Corrosion Resistance

The corrosion performance gap between A360 and A380 is primarily driven by copper content. Copper in aluminum alloys forms intermetallic precipitates (CuAl2 at grain boundaries. These precipitates are cathodic relative to the aluminum matrix, creating micro-galvanic couples that accelerate corrosion in wet or chloride environments. A380's 3.0-4.0% copper produces a dense network of these precipitates; A360's 0.60% maximum copper dramatically reduces them.

In salt spray testing per ISO 9227, A360 die castings regularly survive 500-1,000 hours before significant corrosion -compared to 200-300 hours for equivalent A380 castings without surface treatment. For outdoor, coastal, and marine applications where bare or minimally coated aluminum is exposed to the atmosphere, this difference is significant.

The magnesium addition (0.4-0.6%) further improves A360's corrosion performance by promoting a more uniform and coherent natural oxide layer on the alloy surface.

Thermal Conductivity

A360's thermal conductivity of 113 W/m·K is 18% higher than A380's 96 W/m·K. This difference translates directly into heat dissipation performance:

• A heat sink housing designed in A360 will operate at a lower steady-state temperature than the same geometry in A380 under identical heat loading
• Motor housings in A360 conduct winding and bearing heat to the outer surface more effectively, enabling higher continuous power ratings or smaller frame sizes
• Liquid-cooled manifolds in A360 transfer heat to the coolant more efficiently

For high-power electronics, industrial drives, and motor frames where thermal performance is a design constraint, specifying A360 over A380 is a no-cost upgrade that improves thermal performance by approximately 15-20%.

---

Castability of A360

A360 casts slightly differently from A380 in practice:

Fluidity: A360's fluidity is somewhat lower than A380 due to the higher liquidus temperature and absence of copper. For thin-wall castings (below 1.5 mm wall), this may require slightly higher metal and die temperatures or increased injection velocity compared to A380.

Die soldering resistance: The low copper content reduces A360's tendency to solder to the die -a benefit for tool maintenance. However, the magnesium content can oxidize rapidly at the melt surface if protective measures are not taken. KastMfg uses covered furnaces and controlled melt hold times for A360 production.

Machinability: A360 is slightly less machinable than A380 -the lower copper content reduces chip breakability, leading to longer chips in some operations. For programs with extensive post-casting machining, this is a consideration. In practice, the difference is manageable with appropriate tooling selection.

---

A360 vs A380 -When to Choose A360

Factor	Choose A360	Choose A380
Service environment	Outdoor, marine, humid industrial	Indoor, dry, protected environments
Primary function	Heat dissipation	General structural/enclosure
Corrosion protection	Bare or minimal coating	Painted, powder coated, fully protected
Thermal conductivity	Critical	Standard requirement
Machining volume	Moderate	Extensive
Cost premium	~3-% material premium	Baseline

For most indoor industrial applications in controlled environments, A380 is adequate and the correct choice. For applications where the casting will be exposed to the elements, where salt air or humidity are factors, or where thermal performance constrains the design, A360 is worth the modest cost premium.

---

Applications

Outdoor and Marine Equipment

• Outdoor lighting fixture bodies (streetlights, floodlights, area lights)
• Marine hardware and equipment housings
• Agricultural machinery components exposed to weather and fertilizer spray
• Irrigation equipment bodies
• Telecommunications equipment enclosures for outdoor deployment

Thermal Management

• Power electronics heat sink housings
• Motor and generator frame components (improved thermal path to ambient)
• EV charging station enclosures
• Industrial drive housings requiring superior heat dissipation
• Liquid-cooled cold plate housings

Chemical and Process Industries

• Pump housings for mild chemical service
• Valve and actuator bodies in food processing environments
• Instrumentation enclosures in aggressive atmospheres

---

Surface Finishing

A360's lower copper content improves anodizing quality compared to A380. The anodized layer on A360 is more uniform and consistent in appearance, making A360 the better choice when Type II anodizing is specified for both corrosion protection and appearance.

Finish	A360 Suitability	Notes
Type II Anodizing	Excellent	Better quality than A380; uniform clear or colored layer
Type III Hard Anodizing	Good	Suitable for wear surfaces
Powder Coating	Excellent	Standard preparation applies
Chromate Conversion	Good	Slightly different process parameters vs A380
E-coating	Excellent	Standard process

---

Equivalent Designations

Standard	Designation
ASTM B85 (USA)	A360.0
EN 1706 (Europe)	EN AC-43400 (approximate)
JIS H5302 (Japan)	ADC3 (similar, not identical)
BS 1490 (UK)	LM9 (approximate)

---

Frequently Asked Questions

Is A360 significantly more expensive than A380?

A360 commands a 3-% material cost premium over A380, primarily due to the controlled magnesium addition and tighter copper limit requiring higher-purity base metal. At typical casting weights and volumes, this translates to a cost difference of cents per part -rarely a deciding factor when the application genuinely warrants A360's performance advantages.

Can A360 be used for the same tooling as A380?

Yes, with minor process adjustments. The same H13 die used for A380 can run A360. Metal temperature and injection parameters require slight adjustment; die temperature management may need optimization due to the different fluidity characteristics. KastMfg's process engineers handle this transition as part of the program setup.

Does A360 require T6 heat treatment?

Standard A360 HPDC as-cast properties are adequate for most applications. T6 heat treatment is possible on vacuum-assisted or low-pressure die cast A360 (low enough porosity to prevent blistering during solution treatment), improving tensile strength to approximately 300-320 MPa and yield to 230-250 MPa. Contact KastMfg to discuss T6 capability for specific programs.

---

A360 die casting inquiry: yaoqingpu1983@gmail.com | +86 138 1403 4409 | No.6, Rungu Road, Nanjing, China