Shenzhen Alu Rapid Prototype Precision Co., Ltd.
Industry News
Pure zinc alone has significant limitations for die casting. Alloying elements dramatically improve its properties.
Problems with Pure Zinc
Problem | Detail |
Brittle | Cracks easily under stress or impact |
Weak | Low tensile and yield strength |
Poor fluidity | Doesn't fill thin sections well |
Unstable dimensions | Creeps and shrinks over time |
Coarse grain structure | Poor surface finish |
Corrosion issues | Intergranular corrosion over time |
Key Alloying Elements and What They Do
Aluminum (3.5 – 4.3%)
The most important alloying element in Zamak alloys.
✅ Increases strength and hardness
✅ Improves fluidity — fills thin walls better
✅ Reduces grain size — finer, stronger structure
✅ Lowers melting point — easier to cast
✅ Reduces zinc-iron reaction — protects die
Copper (0.75 – 1.25%)
✅ Increases hardness and tensile strength
✅ Improves wear resistance
✅ Better creep resistance at elevated temps
❌ Reduces ductility slightly
❌ Reduces corrosion resistance slightly
Magnesium (0.03 – 0.06%)
Small amount but very important.
✅ Prevents intergranular corrosion
✅ Improves surface finish
✅ Reduces hot cracking during solidification
✅ Controls lead/cadmium impurity effects
How Alloys Compare to Pure Zinc
Property | Pure Zinc | Zamak 3 (Alloy) | Improvement |
Tensile strength | ~120 MPa | ~283 MPa | 2.4× stronger |
Yield strength | ~80 MPa | ~221 MPa | 2.8× stronger |
Hardness | ~30 HB | ~82 HB | 2.7× harder |
Elongation | ~1% | ~10% | 10× more ductile |
Fluidity | Poor | Excellent | Much better fill |
Dimensional stability | Poor | Good | Stable over time |
Surface finish | Rough | Excellent | Plating-ready |
Common Zinc Die Cast Alloys
Alloy | Al% | Cu% | Mg% | Best For |
Zamak 2 | 4.0 | 2.7 | 0.035 | Highest strength & hardness |
Zamak 3 | 4.0 | 0.1 | 0.035 | General purpose, most used |
Zamak 5 | 4.0 | 1.0 | 0.035 | Better strength than Zamak 3 |
Zamak 7 | 4.0 | 0.1 | 0.020 | High ductility, thin walls |
ZA-8 | 8.4 | 1.0 | 0.020 | Higher strength, gravity cast |
Manufacturing Benefits of Alloying
Better Castability
Lower melting point than pure zinc
Improved fluidity fills complex, thin-walled molds
Reduced porosity in finished parts
Less shrinkage during solidification
Longer Die Life
Pure zinc attacks steel dies aggressively
Aluminum in alloy forms protective layer
Dramatically extends expensive die tool life
Faster Cycle Times
Better fluidity = faster mold filling
More consistent solidification
Higher productivity per hour
Impurity Control — Critical in Zinc Alloys
Certain impurities destroy zinc die cast quality even in tiny amounts:
Impurity | Max Allowed | Effect if Exceeded |
Lead | 0.003% | Intergranular corrosion |
Cadmium | 0.002% | Intergranular corrosion |
Tin | 0.001% | Brittleness, cracking |
Iron | 0.075% | Hard spots, poor finish |
Magnesium in the alloy helps neutralize some impurity effects — another reason pure zinc fails in practice.
Bottom Line
Reason | Why It Matters |
Strength | Parts can handle real loads |
Ductility | Won't shatter on impact |
Fluidity | Can cast complex thin-wall parts |
Stability | Parts stay dimensionally accurate |
Die protection | Tooling lasts millions of cycles |
Surface quality | Ready for plating and finishing |
Corrosion resistance | Longer service life |
Pure zinc is simply too weak, too brittle, and too unstable for pressure die casting production. Alloying transforms it into one of the most versatile and cost-effective die casting materials available.