Guide
Zinc vs aluminum die casting: which one should your part use?
Zinc vs aluminum die casting is the choice between two alloy families that run on different machines and pay off in different places. Zinc alloys such as Zamak 3 are cast hot-chamber at low temperature and reward small, detailed, plated or leak-sensitive parts. Aluminum alloys such as A380 and ADC12 are cast cold-chamber and reward parts where weight, size and heat matter more.
By Saola Manufacturing engineering team · Published · Updated
This guide is for mechanical engineers and sourcing managers who have a die-cast part on the drawing board, or a quote in one alloy for a part drawn in the other. Most comparisons stop at “zinc is heavy, aluminum is light”. That is true and rarely decides the question. What decides it is how the alloy changes wall thickness, draft, die life, machining and finishing, and therefore the cost of each good part over the life of the program.
Every figure below comes from a free primary or trade-association source: International Zinc Association engineering data, NADCA design pages and the ASTM scope summary for zinc castings. Paid standards are named but not quoted. The two alloys Saola sources from its partner foundries are ADC12 aluminum and Zamak 3 zinc, so those are the pair this page compares.
On this page
What is the real difference between zinc and aluminum die casting?
The deciding difference is the process each alloy allows: zinc melts low enough to be cast on a hot-chamber machine, while aluminum has to be ladled into a cold-chamber machine. Almost every other difference, from die life to cycle speed to how thin a wall can be, follows from that.
On a hot-chamber machine the injection plunger sits in the molten metal bath, so each shot is drawn straight from the furnace. NADCA describes this route as the one used for zinc, magnesium and other low-melting alloys that do not readily attack the pot, cylinder and plunger (NADCA, hot chamber process). Aluminum would erode that hardware, so it is poured into a separate sleeve for every shot (NADCA, cold chamber process). The extra ladling step is one reason hot-chamber machines are typically smaller and faster for the same casting size.
Temperature is the second half of the story. Zamak 3 melts at 381–387 °C in the International Zinc Association’s property data (IZA, physical properties), while NADCA lists alloy 380 at 1000–1100 °F, roughly 540–590 °C (NADCA, Table 4.3). A die that sees a cooler metal suffers less thermal fatigue, which is where zinc’s long die life comes from.
How do Zamak 3 and 380-family aluminum compare on paper?
The table sets Zamak 3 against the 380 aluminum family, using only published association data. Zinc wins on die life, draft, impact at room temperature and pressure tightness; aluminum wins on weight, melting point and behavior under sustained load and heat.
ADC12 is not listed as its own column because its limits sit in JIS H 5302, a paid standard. It is a close relative of 380 and 383, not an exact equivalent; the ADC12 vs A380 guide explains the difference.
| Property | Zamak 3 zinc | 380-family aluminum |
|---|---|---|
| Designations | ASTM B86 Alloy 3 (AG40A, UNS Z33525); EN 12844 ZP3; JIS H 5301 ZDC2 | AA 380.0 / A380.0 per ASTM B85; ADC12 (JIS H 5302) is a close relative |
| Specific gravity | 6.6 (alloy, zero porosity) | 2.7 (aluminum element) |
| Melting range | 381–387 °C | 1000–1100 °F (alloy 380) |
| Machine type | Hot chamber | Cold chamber |
| Typical die life | About 1,000,000 shots; allow at least 500,000 | About 200,000 shots |
| Minimum draft (normal) | 1° internal, 0.5° external, 0.1° round holes; 0° possible on some features | More than zinc; values in the NADCA standards (not published here) |
| Tensile strength, as cast | 315 MPa (1.5 mm specimen, 8 weeks after casting) | Not published here (ASTM B85) |
| Unnotched impact, 20 °C / 0 °C / −20 °C | 116 / 44 / 11 J/cm² | Varies by alloy (NADCA); no comparable low-temperature data published |
| Pressure tightness | “Much more often pressure tight” than aluminum die castings | 380 rated 2 on a 1–5 scale (1 best); 413 rated 1 |
| Sustained load and heat | Creeps under long-term load; account for it in design | Keeps properties over a wider temperature range |
| Thermal conductivity | 113 W/m·°C | Not published here |
The zinc figures come from IZA test specimens, so use them to rank the alloys, not as design allowables. The aluminum column is deliberately thin: the registered values for 380 live in ASTM B85, which the drawing should cite.
Which alloy allows thinner walls, less draft and tighter as-cast features?
Zinc does. It fills thinner sections, releases from the die with less draft and can hold features such as zero-draft bores and press-fit diameters as cast, which on an aluminum part would usually be machined.
NADCA notes that die casters currently cast thinner walls in zinc and magnesium than in aluminum, and that zero draft and press-fit tolerances can often be held as cast in zinc (NADCA, alloy selection). The IZA rule of thumb ties minimum wall to flow distance: under 0.5 mm for features close to the gate, rising to about 2 mm at around 200 mm of flow (IZA, design rules). The same page gives normal minimum draft for zinc as 1° on internal walls and 0.5° on external walls, and says zero draft can be held reliably on some critical features.
For the tolerance itself, NADCA publishes separate standard and precision values for each alloy family; the tolerance guide explains how to call them out. The practical consequence is on the routing, not the drawing. If a bore, a thread or a datum face would need a second operation in aluminum, check whether zinc removes it. If it does, the heavier alloy can still be the cheaper part. If the feature will be machined either way, the zinc advantage shrinks, and machining after casting becomes part of both quotes.
Which is cheaper per part, zinc or aluminum?
For small parts, and for parts where zinc removes machining or outlasts several aluminum dies, zinc is often cheaper per part despite costing more per unit volume. For larger parts where the walls are set by function, aluminum usually wins on material alone.
Start with material. Alloy is bought by weight but a design uses volume, so NADCA recommends comparing cost per cubic inch, and on that basis aluminum is usually the lowest-cost die casting alloy (NADCA, alloy selection). With a specific gravity near 6.6 against 2.7, the same volume of Zamak 3 weighs about two and a half times as much. Zinc wins some of that back only where it lets the wall get thinner.
Then add the terms that change with the alloy. A useful way to build the comparison is:
- Material: part volume × density × alloy price, plus runner and overflow metal that is remelted.
- Machine time: hot-chamber cycles are typically faster, and NADCA notes that zinc is the usual choice for very small castings made on dedicated miniature machines.
- Die amortization: die cost divided by die life, multiplied by the number of dies the program will need.
- Secondary operations: machining, impregnation and finishing that one alloy needs and the other does not.
The die term is where programs are most often misjudged. Both NADCA and the IZA state that the first die costs essentially the same whichever alloy it casts (IZA, tooling). The difference is how long it lasts: the IZA suggests allowing at least 500,000 shots for a zinc die, with about a million as typical, against around 200,000 for aluminum. On a program of a million parts that can mean one zinc die against several aluminum ones. As a published industry range, the IZA puts zinc die prices at €3,000 to €100,000, from small single-cavity tools to large multi-cavity dies with slides; your own die price depends on the part and belongs in a written quote.
When sourcing from Asia, ask for these terms broken out and for both alloys quoted on the same annual volume; a single piece price hides the die-life and machining terms that decide the answer.
Which alloy is more pressure tight for fluid and gas parts?
Zinc die castings are more often pressure tight than aluminum ones, according to the zinc industry’s own design data. Aluminum parts that must hold pressure are commonly impregnated after machining, which adds a process and a cost.
The IZA explains the mechanism: aluminum die castings more often need finish machining, and machining opens the subsurface porosity that causes leaks, so impregnation becomes normal for fluid-handling aluminum parts (IZA, comparison with alternative materials). NADCA’s aluminum ratings point the same way within the aluminum family: 380 rates 2 for pressure tightness, while 413 rates 1 and is the alloy NADCA names for hydraulic cylinders and pressure vessels.
Treat both statements as tendencies, not guarantees. Porosity depends on wall uniformity, gating and process control as much as on alloy. For valve bodies, meter housings or fittings, write the leak test on the drawing (medium, pressure, hold time and allowed leak rate) and ask whether the quote includes impregnation. A zinc part that passes without it and an aluminum part that needs it are not priced on the same basis.
When is aluminum the better choice?
Choose aluminum when the part is large, when weight counts, when it runs hot or carries a sustained load for years, or when it will see impact in freezing conditions. Those are the four places where zinc’s advantages stop.
NADCA points to aluminum’s combination of low density and relatively high strength as why bigger, load-bearing die castings tend to go to aluminum, and it rates aluminum ahead of zinc for holding its strength as operating temperature climbs (NADCA, alloy selection). Zinc, by contrast, creeps in a way NADCA compares to the visco-elastic behavior of thermoplastics, so a clamp, bracket or boss that stays under load needs its stress checked against creep data.
Cold service is the other trap. Zinc has the highest room-temperature impact strength of the die casting alloys, but NADCA warns that it begins to fall sharply below 32 °F (0 °C), and the IZA impact data shows unnotched Zamak 3 dropping from 116 to 11 J/cm² between 20 and −20 °C (IZA, mechanical properties). An outdoor housing that may be knocked in winter is a better aluminum part, or a zinc part designed with that loss in mind.
Which finishes work on zinc and on aluminum die castings?
Zinc takes almost any finish, including bright decorative chrome and nickel plating, while aluminum die castings are usually painted or powder coated. High-silicon aluminum die castings are a poor base for cosmetic anodizing.
NADCA calls zinc the die casting material of choice for hardware because it can be economically plated to a bright, durable chrome finish (NADCA, zinc alloys). The IZA goes further and describes electroplating of aluminum die castings as impractical, which limits the metallic finishes available on them. NADCA’s Table 4.3 does rate 380 well for electroplating, but that scale only compares aluminum alloys with each other, so confirm plating on aluminum with the finisher before you design around it.
For a painted or powder-coated part, both alloys work, and the choice falls back on the other factors in this guide. The finishing guide compares the main options, and the surface finishing page lists the finishes our partner plants apply, and the quote names where each step is done.
How should the alloy be written on the drawing and the RFQ?
Name one alloy and one governing standard, in full, for example “Zinc Alloy 3 per ASTM B86” or “A380.0 per ASTM B85”. If a supplier quotes a local grade name, ask it to state the grade and its standard in writing.
Suppliers in Asia commonly quote Japanese grade names. For zinc that is ZDC2, which the IZA lists as the JIS H 5301 equivalent of Zamak 3, alongside ASTM AG40A, SAE 903 and EN 12844 ZP3, and says the equivalent specifications can be used interchangeably (IZA, alloy specifications). ASTM B86 itself lists Alloy 3 as UNS Z33525 and covers the zinc and zinc-aluminum alloys used for castings (ASTM B86-23, scope). For aluminum the local name is usually ADC12, which is a close relative of A380 rather than the same alloy.
Three lines on the RFQ save a round of questions. State whether the alloy is fixed or open to a proposal, so a supplier can suggest the other family where it would remove machining. List the features you expect to be held as cast and those you expect to be machined. And give the annual volume and program life, because die life only changes the answer when the quantity is known. The RFQ preparation guide covers the rest of the package, and the die casting page describes the ADC12 and Zamak 3 castings sourced from partner foundries and machined at our lead CNC plant.
Frequently asked
Is Zamak 3 stronger than die-cast aluminum?
The zinc industry’s design data lists higher tensile strength and far higher impact strength among zinc’s advantages over aluminum die castings at room temperature. Aluminum keeps its strength better when hot and under sustained load, so the answer depends on the service conditions, not the alloy alone.
Is ZDC2 the same as Zamak 3?
The IZA lists JIS H 5301 ZDC2 as the equivalent of Zamak 3 (ASTM Alloy 3, EN 12844 ZP3). If your drawing names ASTM B86, ask for the lot chemistry to be reported against B86 rather than the Japanese standard.
Can an aluminum die-cast part be switched to zinc using the same die?
No. Aluminum is cast cold-chamber and zinc hot-chamber, and a part converted to zinc is usually redesigned with thinner walls and less draft. Plan for a new die and a new first-article inspection.
Does zinc die casting corrode?
It can. NADCA notes that the alloy standards cap lead, cadmium and tin impurities specifically to prevent intergranular corrosion, so buy to a named specification such as ASTM B86. For outdoor or humid service, specify a finish and a salt-spray requirement on the drawing.
Which die-casting alloys can a Saola order use?
ADC12 aluminum and Zamak 3 zinc, no others, cast by partner foundries we manage; the quote names the production site and origin. If you are undecided between them, send the drawing for a quote and say the alloy is open, so both can be discussed before tooling.
Sources
- Zinc Diecasting Alloys: Physical Properties, International Zinc Association, 2019 (accessed September 2026)
- Zinc Diecasting Alloys: Mechanical Properties, International Zinc Association, 2019 (accessed September 2026)
- Zinc Diecasting Alloys: Comparison with Alternative Materials, International Zinc Association, 2019 (accessed September 2026)
- Zinc Diecasting Alloys: Design Rules, International Zinc Association, 2019 (accessed September 2026)
- Zinc Diecasting Alloys: Tooling, International Zinc Association, 2019 (accessed September 2026)
- Zinc Diecasting Alloys: Alloy Specifications, International Zinc Association, 2019 (accessed September 2026)
- ASTM B86-23, Standard Specification for Zinc and Zinc-Aluminum (ZA) Alloy Foundry and Die Castings (scope), ASTM International, 2023
- Alloy Selection, NADCA Design, North American Die Casting Association, accessed September 2026
- Aluminum Alloys, including Table 4.3, NADCA Design, accessed September 2026
- Zinc Alloys, NADCA Design, accessed September 2026
- Hot Chamber Process and Cold Chamber Process, NADCA Design, accessed September 2026