Zinc alloy presents challenges around strength, corrosion, brittleness, and machinability that makers and sellers must weigh before selecting it for a given application.
Key Takeaways
- Zinc alloys have limited mechanical strength and are not suitable for structural or heavy-duty jobs.
- Zinc alloys corrode faster in wet or salty environments; protective coatings extend service life.
- Welding and machining zinc alloys requires skilled workers and specialist tooling, raising production costs.
Zinc Alloy Strength Limitations
Mechanical strength
Most zinc alloys, including zamak grades, have tensile strengths of 170–300 MPa. Zamak with copper and titanium additions can reach 300 MPa, and adding magnesium raises strength a further 15–25%. Even so, zinc alloys fall short of steel and aluminum die-castings. Fatigue resistance sits between 80 and 120 MPa, making zamak unsuitable for heavy-duty or structural applications.
| Material/Process | Advantage Over Zinc Alloy Diecasting |
|---|---|
| Aluminium Diecasting | Lighter and better at handling stress when it gets hot. |
| Magnesium Alloys | Very low density, so they are good for things that need to be light. |
| Plastic Injection Moulding | Stiffer and more reliable. |
| Steel Pressings | Very strong and cost-effective. |
Durability Issues
Zinc alloys, like zamak, have some problems with durability. These problems include:
- Tarnishing when there is moisture or humidity.
- Corrosion from things like perfumes, lotions, or cleaners.
- Surface damage from sweat, which has acids and salts.
- Coatings can wear off when touched a lot.
- The zinc layer can bubble in humid air.
- More corrosion happens in acid, base, or salty places.
Factories and sellers use zamak because it is cheap. But they must think about these risks. Special solutions, like those from MORELUX Precision Die-Casting Solutions, can help with some problems. Still, zinc alloys have basic limits in tough places. Zamak can bend a little, but too much stress or exposure can make it break.
Zinc Alloy Corrosion Risks
Environmental sensitivity
Zinc alloy lasts longest indoors where air is clean. In industrial or coastal environments it degrades far more rapidly. Indoors, corrosion rates can be as low as 0.1 µm/year; in polluted or salt-laden air, rates can exceed 10 µm/year. A zinc alloy part may therefore last over 100 years in a benign environment but fail within a year in a harsh one.
| Category | Corrosion Rate (µm/year) | Corrosion Rate (oz/ft²/year) |
|---|---|---|
| C1 | ≤ 0.1 | ≤ 0.0023 |
| C2 | 0.1 < R ≤ 0.7 | 0.0023 < R ≤ 0.016 |
| C3 | 0.7 < R ≤ 2.1 | 0.016 < R ≤ 0.049 |
| C4 | 2.1 < R ≤ 4.2 | 0.049 < R ≤ 0.097 |
| C5 | 4.2 < R ≤ 8.4 | 0.097 < R ≤ 0.19 |
pH, temperature, and moisture all influence corrosion rate. Zinc performs best at pH 5–11.5; elevated heat and humidity accelerate attack. Sulfur dioxide or chlorides in the air break down the protective surface layer, increasing corrosion further.
Zinc pest and degradation
Zinc pest causes the metal to expand, crack, or disintegrate over time. Humid air and thermal cycling accelerate the process. Even alloys with good baseline corrosion resistance can suffer zinc pest if metal purity is low or service conditions are severe. Protective coatings and surface treatments slow degradation and extend service life.
Zinc Alloy Metal Brittleness
Cracking under stress
Zinc alloy can crack under excessive or repeated pressure. Small electronic components can develop microcracks during use; moisture and heat cause these cracks to propagate, exposing fresh metal to corrosion and ultimately causing part failure.
| Property | Zinc Alloy #3 | Zinc Alloy #5 |
|---|---|---|
| Tensile Strength | 283 MPa | 310-317 MPa |
| Yield Strength | 221 MPa | 240 MPa |
| Brinell Hardness | 82 | 90-91 |
| Ductility | Better | Lower |
Impact resistance
Zinc alloy absorbs shock less effectively than aluminum. Dropped or impacted parts may fracture rather than deform, and brittleness worsens at low temperatures. Zinc Alloy #3 bends better and cracks less under sudden force; Zinc Alloy #5 is stronger but more likely to break if dropped. Selecting the correct grade reduces failure risk but cannot eliminate cracking and impact hazards entirely.
Zinc Alloy Weldability Challenges
Welding issues
High heat causes zinc to vaporize, producing porosity and weak spots in welds. Weld spatter increases cleaning time and cost. Welds crack when parts are poorly fitted, cooling is too rapid, or contamination is present; hot cracks appear above 1000 °F and run along or adjacent to the weld line. Repairing or scrapping cracked parts adds further cost.
| Welding Technique | Effectiveness | Limitations |
|---|---|---|
| Conventional Soldering | Works well if cleaned first | Needs careful cleaning; too much heat melts the alloy |
| Pulsed-arc Welding | Good for joining | Not specified |
| Gas Welding | Used for fixing parts | Not for new joints |
Machining difficulties
Zinc’s low melting point means parts can distort or develop surface flaws from machining heat. Its ductility promotes burr and rough-edge formation, requiring sharp tooling and careful technique. Cutting tools wear rapidly, necessitating frequent changes or specialist coatings. Zinc alloys can behave adhesively during cutting, slowing throughput and raising per-part cost, particularly at high production volumes.
| Difficulty Type | Description |
|---|---|
| Heat Management | Too much heat bends parts and makes surface problems. |
| Burr Minimization | Burrs and rough edges happen; sharp tools help. |
| Tool Wear | Tools need to be changed or coated often. |
Zinc alloys can act sticky when machined. This slows down work and costs more. Special methods and tool changes make making zinc alloy parts cost more, especially when making many parts.
Zinc alloy and zinc alloy metal have some problems. They are not very strong. They can rust and break easily. These problems can hurt car parts and other things. Makers and sellers must think about how they will use zinc alloy. The table below shows how these problems change how things work. Talking to experts like MORELUX can help pick the best solution.
| Disadvantage | Impact on Performance |
|---|---|
| Limited structural stability | Not suitable for high-heat parts |
| Upper load capacity | Better for small and medium parts |
| Chemical stability | Needs extra coatings |
FAQ
What industries use zinc alloy components?
Zinc alloy is used in automotive, electronics, medical, and consumer electronics applications, particularly for complex shaped parts in high-volume production.
Can zinc alloy parts resist corrosion?
With appropriate coatings and surface treatments, zinc alloy parts can resist corrosion in demanding environments.
Is zinc alloy easy to recycle?
Zinc alloy recycles efficiently; suppliers collect scrap metal and reprocess it into new material.