## Common ground
All options are coach screws made from different metallic materials.
## Options at a glance
**7318.11 – Iron or steel**
- **Defining trait:** Most common material; offers high strength and affordability.
- **Typical examples:** Standard construction screws, furniture assembly fasteners.
- **Best fit when:** High durability and load-bearing capacity are needed.
**7415.33 – Copper**
- **Defining trait:** Excellent corrosion resistance and electrical conductivity.
- **Typical examples:** Electrical grounding screws, marine hardware.
- **Best fit when:** Use in corrosive environments or electrical applications.
**7508.90 – Nickel**
- **Defining trait:** High resistance to oxidation and heat; often used for plating.
- **Typical examples:** Aerospace fasteners, high-temperature industrial parts.
- **Best fit when:** Extreme environmental or thermal conditions.
**7616.10 – Aluminium**
- **Defining trait:** Lightweight with good corrosion resistance.
- **Typical examples:** Aircraft components, lightweight fixtures.
- **Best fit when:** Weight reduction is critical and strength needs are moderate.
**7907.00 – Zinc**
- **Defining trait:** Often used as a coating (galvanization), not typically for structural use alone.
- **Typical examples:** Galvanized screws, outdoor fasteners.
- **Best fit when:** Corrosion protection via coating is the main purpose.
**8101.99 – Tungsten**
- **Defining trait:** Extremely high density and melting point; very hard but brittle.
- **Typical examples:** Specialized industrial tools, not common for general screws.
- **Best fit when:** Extreme hardness or high-temperature resistance is required.
**8102.99 – Molybdenum**
- **Defining trait:** High melting point and strength at elevated temperatures.
- **Typical examples:** Aerospace or chemical processing equipment fasteners.
- **Best fit when:** Use in high-heat, high-stress environments.
**8104.90 – Magnesium**
- **Defining trait:** Lightest structural metal; prone to corrosion and flammability.
- **Typical examples:** Aerospace or automotive components.
- **Best fit when:** Weight savings outweigh material limitations.
**8108.90 – Titanium**
- **Defining trait:** Excellent strength-to-weight ratio and corrosion resistance.
- **Typical examples:** Medical implants, aerospace, marine applications.
- **Best fit when:** High performance with long-term durability in harsh conditions.
## Key differences
| Material | Strength | Weight | Corrosion Resistance | Heat Resistance |
|----------------|----------|--------|------------------------|------------------|
| Iron/Steel | High | Medium | Low (unless coated) | Medium |
| Copper | Medium | Medium | Very High | Low |
| Nickel | High | Medium | Very High | High |
| Aluminium | Medium | Low | High | Medium |
| Zinc | Low | Medium | High (as coating) | Low |
| Tungsten | Very High| High | Medium | Very High |
| Molybdenum | High | Medium | Medium | Very High |
| Magnesium | Low | Very Low | Low | Low |
| Titanium | High | Low | Very High | High |
## How to choose
- Is the screw used in a corrosive environment (e.g., marine, outdoor)? → 7415.33, 7616.10, 8108.90
- Does weight matter most? → 7616.10, 8104.90, 8108.90
- Is high strength or heat resistance critical? → 8101.99, 8102.99, 8108.90
- Is it for general construction or everyday use? → 7318.11
## Overlaps & pitfalls
A screw may combine traits (e.g., titanium-coated aluminum). If multiple materials apply, prioritize the **primary structural material**. Zinc is often a coating—use 7907.00 only if the base is zinc. Magnesium and tungsten are rare; confirm intended use