## Common ground
All options are bolt ends made from different metallic materials, used to secure or connect mechanical components.
## Options at a glance
**7318.15 – Iron/steel**
- **Defining trait:** High strength and cost-effectiveness; commonly used in general industrial applications.
- **Typical examples:** Carriage bolts, machine screws, structural fasteners.
- **Best fit when:** Durability and load-bearing capacity are key, and cost is a concern.
**7415.33 – Copper**
- **Defining trait:** Excellent electrical conductivity and corrosion resistance; used in specialized environments.
- **Typical examples:** Electrical connectors, marine hardware, high-purity applications.
- **Best fit when:** Conductivity or resistance to oxidation is required (e.g., in wet or corrosive settings).
**7508.90 – Nickel**
- **Defining trait:** High corrosion and heat resistance; ideal for extreme conditions.
- **Typical examples:** Aerospace components, chemical processing equipment.
- **Best fit when:** Exposure to high temperatures or aggressive chemicals.
**7616.10 – Aluminium**
- **Defining trait:** Lightweight with moderate strength; resists corrosion but less durable under heavy load.
- **Typical examples:** Aircraft parts, consumer electronics, outdoor fixtures.
- **Best fit when:** Weight reduction is critical and loads are light.
**7907.00 – Zinc**
- **Defining trait:** Often used as a coating (galvanizing), but can be structural in low-stress applications.
- **Typical examples:** Galvanized fasteners, decorative hardware.
- **Best fit when:** Corrosion protection via plating or low-cost, non-critical use.
**8101.99 – Tungsten**
- **Defining trait:** Extremely high density and melting point; used in extreme environments.
- **Typical examples:** High-temperature fasteners, radiation shielding components.
- **Best fit when:** Exceptional heat or wear resistance is needed.
**8102.99 – Molybdenum**
- **Defining trait:** High thermal stability and strength at elevated temperatures.
- **Typical examples:** Aerospace, furnace components.
- **Best fit when:** Operation under high heat without deformation.
**8104.90 – Magnesium**
- **Defining trait:** Very lightweight; prone to corrosion and flammability.
- **Typical examples:** Racing or aerospace parts where weight is critical.
- **Best fit when:** Weight savings outweigh durability concerns.
**8108.90 – Titanium**
- **Defining trait:** Excellent strength-to-weight ratio and corrosion resistance.
- **Typical examples:** Medical implants, high-performance aircraft, marine hardware.
- **Best fit when:** High strength, light weight, and long-term durability in harsh environments.
## Key differences
| Material | Strength | Weight | Corrosion Resistance | Heat Resistance | Cost |
|---------------|----------|--------|------------------------|------------------|------|
| Iron/Steel | High | Medium | Low–Medium | Medium | Low |
| Copper | Medium | Medium | High | Low | Medium |
| Nickel | High | Medium | Very High | Very High | High |
| Aluminium | Medium | Low | High | Low | Medium |
| Zinc | Low | Medium | High (as coating) | Low | Low |
| Tungsten | Very High| High | Medium | Extremely High | Very High |
| Molybdenum | High | Medium | Medium | Extremely High | Very High |
| Magnesium | Low | Very Low | Low | Low | Medium |
| Titanium | High | Low | Very High | High | High |
## How to choose
- Is the application exposed to high heat or extreme environments? → 8101.99, 8102.99, 7508.90, 8108.90
- Does weight matter most (e.g., aerospace)? → 7616.10, 8104.90, 8108.90
- Is electrical conductivity needed? → 7415.33
- Is corrosion resistance critical in harsh environments? → 7508.90, 7616.10, 8108.90
- Is cost the main factor? → 7318.15, 7907.00
## Overlaps & pitfalls
A product may fit multiple categories (e.g., titanium is lightweight and corrosion-resistant). If a bolt end is both light and corrosion-resistant, prioritize **main function**: use 8108.90 for aerospace, 7616.10 for general light-duty use. Avoid assuming material implies coating—zinc is often used as plating, not bulk material