Zamak 3
Specifying zinc Alloy 3 by ingot/casting requirements, with bounded typical properties, aging and creep considerations and finished-part acceptance.
Tags: materials, zinc-alloys, die-casting, specialty-metals
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Identity and specification
Eastern Alloys gives 0.10% maximum copper in both its ASTM B240 Zamak 3 ingot and ASTM B86 die-cast rows. Its 283 MPa tensile strength is typical from net-shaped die-cast test bars. Use the finished-casting requirements and relevant inspection evidence for part acceptance. Eastern Alloys ingot and casting chemistry, Eastern Alloys test-bar data
Zamak 3 is a conventional zinc die-casting alloy, also called Alloy 3, ZP3 or ZnAl4 in the International Zinc Association's alloy overview. It belongs to the ZAMAK family, distinct from the higher-aluminum ZA family. A familiar short name does not establish the precise purchasing standard or a finished component's properties. IZA alloy overview
Specify alloy, standard edition, supplied form, casting route, drawing, surface treatment and required inspection documentation. Distinguish alloy ingot used for remelting from the die casting produced from it. ASTM identifies B240 for ingot and B86 for foundry and die castings; an ingot certificate is not finished-casting acceptance evidence. ASTM B240 publisher scope · ASTM B86 publisher description
For an existing part, retain the actual alloy identification instead of inferring it from appearance, mass or the word “zinc.” Review substitutions against dimensions, load, creep, finishing and production requirements together.
Chemistry: ingot and casting rows differ
Eastern Alloys lists the following selected composition limits for its Zamak 3, with zinc as the balance. These are its published standard-associated rows, not a replacement for the complete governing specification or delivered analysis. Eastern Alloys Zamak 3 chemistry
| Basis identified by producer | Aluminum, % | Magnesium, % | Copper, maximum % |
|---|---|---|---|
| Ingot, ASTM B240 | 3.9–4.3 | 0.03–0.06 | 0.10 |
| Die cast, ASTM B86 | 3.7–4.3 | 0.02–0.06 | 0.10 |
The full table also limits trace constituents. Check all required elements against the actual product basis rather than accepting a major-element match alone. Preserve melt/lot traceability and resolve any material mixing or undocumented substitution before release.
Typical property example
Eastern Alloys' sheet gives these typical values tested on net-shaped die-cast test bars. It expressly limits them to initial reference/comparison and says they should not establish design limits or quality acceptance/rejection. Eastern Alloys Zamak 3 data sheet
| Property | Published typical value |
|---|---|
| Ultimate tensile strength | 283 MPa |
| Yield strength | 221 MPa |
| Elongation in 2 inches | 10% |
| Brinell hardness | 82 |
| Density | 6.6 g/cm³ |
| Melting range | 381–387°C |
The sheet does not state a complete test-temperature and aging protocol for every entry. Do not silently attach conditions from another organization's table, or promote these values to guaranteed minima for an arbitrary part.
Calculated mass illustration: a nominal solid 50 × 40 × 10 mm blank has volume 20 cm³. At the listed density, estimated mass is 132 g. This assumes solid geometry and excludes tolerances, porosity, finish and attached hardware. The calculation is a preliminary estimate, not a finished-casting weight guarantee. Density basis: Eastern Alloys
A melting range is not a service-temperature rating. For design, obtain appropriate load-, temperature- and time-dependent data for the actual process and section, and use the accepted design basis for the application.
Section thickness, aging and creep
IZA explains that casting conditions affect cooling rate and mechanical properties. Its nominal-property discussion concerns sound castings around 2 mm thick, with original values measured roughly five to eight weeks after casting. It notes that ZP3 strength and hardness decrease with aging while elongation increases, with changes occurring faster at elevated temperature. IZA mechanical-property guidance
Compare results at matching specimen geometry, test age and temperature.
IZA also warns that zinc castings can creep under sustained load, particularly at elevated temperature. Its guidance treats load, temperature and design life as inputs to the creep assessment. IZA creep discussion
For a loaded bracket, threaded connection or clamped joint, define permissible movement, preload loss and time in service. Short-term tensile strength alone cannot answer those questions. Include normal and exceptional heating, and qualify the actual assembly when published data do not match its stress state and geometry.
Casting quality and geometry
IZA identifies trapped gas and solidification shrinkage as sources of die-casting porosity and stresses that pore distribution matters as well as total porosity. Strength-critical regions need attention to soundness. This does not establish a universal acceptable porosity percentage for every function. IZA casting-condition and porosity discussion
Work with the die caster to establish parting, gating, local sections, machining allowance and inspection requirements. Locate critical sealing surfaces, fasteners and highly stressed features explicitly. A visually acceptable exterior does not demonstrate an inaccessible section's condition.
Specify finished-part leak-test pressure, method and acceptance for critical sealing surfaces.
Finishing, comparison and release
IZA identifies plating, painting and conversion-treatment suitability as reasons to select Alloy 3. That qualitative statement does not qualify a particular finish stack or exposure. IZA Alloy 3 characteristics
Specify the surface preparation, finish, thickness where relevant, appearance and corrosion-test requirements with the finisher. Review dimensional effects on threads, fits and contact surfaces. Include cleaning chemicals and environmental exposure in the compatibility assessment; the alloy name cannot establish an unspecified corrosion life.
If creep or strength governs, compare alternative alloys under matched conditions. IZA notes that Alloy 5's improved creep performance accompanies a ductility tradeoff. Selection therefore requires the actual forming, joining, service and finishing requirements rather than a universal upgrade ranking. IZA Alloy 5 comparison
At release, connect the alloy/melt record to the approved drawing, process, finishing route and final inspection. Keep incoming chemistry, representative specimen data and finished-component acceptance distinct. Record any thermal treatment, repair or process change that could alter the original qualification.
Source versions
ASTM's publisher identifies B240-22(2026) and B86-23; only public descriptions/scopes are used here. Eastern Alloys' inspected Zamak 3 PDF displays no technical revision date. Live IZA and Eastern Alloys pages likewise provide no technical revision date used here; website copyright years are not assigned to their data. Sources reviewed 2026-11-01, America/Los_Angeles.