## Common ground
All options refer to fasteners (screws, bolts, nuts) categorized by their primary metallic material.
## Options at a glance
**7318– made of iron or steel**
- **Defining trait:** Most common material; offers high strength and affordability.
- **Typical examples:** Standard machine screws, hex bolts, wing nuts.
- **Best fit when:** General-purpose use in construction, machinery, or DIY projects.
**7415.33– made of copper**
- **Defining trait:** Excellent electrical conductivity and corrosion resistance.
- **Typical examples:** Electrical connectors, marine hardware, decorative fasteners.
- **Best fit when:** Applications requiring conductivity or resistance to saltwater corrosion.
**7508.90– made of nickel**
- **Defining trait:** High corrosion and heat resistance; often used in alloys.
- **Typical examples:** Aerospace components, high-temperature environments.
- **Best fit when:** Harsh environments (e.g., chemical plants, engines).
**7616.10– made of aluminium**
- **Defining trait:** Lightweight with good corrosion resistance; non-magnetic.
- **Typical examples:** Aircraft parts, electronic enclosures, outdoor fixtures.
- **Best fit when:** Weight-sensitive or non-magnetic applications.
**7907.00– made of zinc**
- **Defining trait:** Often used as a coating (galvanization), not typically for structural fasteners alone.
- **Typical examples:** Galvanized bolts, coated screws.
- **Best fit when:** Corrosion protection via plating; not pure zinc fasteners.
**8101.99– made of tungsten**
- **Defining trait:** Extremely high melting point and hardness; rarely used in pure form.
- **Typical examples:** Specialized industrial tools, not standard fasteners.
- **Best fit when:** Extreme heat or wear resistance (e.g., welding equipment).
**8102.99– made of molybdenum**
- **Defining trait:** High strength at elevated temperatures; used in specialized alloys.
- **Typical examples:** High-performance engine parts, furnace components.
- **Best fit when:** Extreme temperature or high-stress environments.
**8104.90– made of magnesium**
- **Defining trait:** Very lightweight but prone to corrosion and flammability.
- **Typical examples:** Aerospace or automotive components (rarely fasteners).
- **Best fit when:** Weight reduction in non-corrosive, non-flammable settings.
**8108.90– made of titanium**
- **Defining trait:** High strength-to-weight ratio and excellent corrosion resistance.
- **Typical examples:** Aerospace, medical implants, high-end sports equipment.
- **Best fit when:** Critical applications needing light weight and durability.
## Key differences
| Material | Strength | Weight | Corrosion Resistance | Common Use Case |
|----------------|----------|---------|------------------------|----------------------------|
| Iron/Steel | High | Medium | Low (unless coated) | General use |
| Copper | Medium | Medium | High | Electrical, marine |
| Nickel | High | Medium | Very high | Harsh environments |
| Aluminium | Medium | Low | High | Lightweight applications |
| Zinc | Low | Medium | Moderate (coated) | Coatings, not pure fasteners|
| Tungsten | Very high| Medium | High | Extreme heat/abrasion |
| Molybdenum | High | Medium | High | High-temp industrial |
| Magnesium | Low | Very low| Low (reactive) | Specialized lightweight |
| Titanium | High | Low | Very high | Aerospace, medical |
## How to choose
- Is the fastener used in a high-temperature or corrosive environment? → 7508.90, 8102.99, 8108.90
- Does weight matter most (e.g., aircraft)? → 7616.10, 8108.90, 8104.90
- Is electrical conductivity needed? → 7415.33
- Is it for general construction or machinery? → 7318
- Is it coated (e.g., galvanized)? → 7907.00 (but note: not pure zinc)
## Overlaps & pitfalls
- Zinc (7907.00) is rarely used as a pure fastener; most are coated steel.
- Tungsten, molybdenum, and magnesium are uncommon for standard fasteners—may be misclassified.
- Titanium and nickel often appear in alloys; check if the product is pure or alloyed.
- **No clear priority**: Choose based on the **primary material** of the fastener itself. If unsure, assume steel (7318) unless otherwise specified