## Common ground
All options are self-locking bolts and nuts categorized by their base metal material.
## Options at a glance
**7318.15 – Iron or steel**
- **Defining trait:** Most common material; offers high strength and durability.
- **Typical examples:** Standard hex bolts with nylon insert, machine screws.
- **Best fit when:** General industrial use, high load-bearing needs, cost-effectiveness is key.
**7415.33 – Copper**
- **Defining trait:** Corrosion-resistant and electrically conductive; non-magnetic.
- **Typical examples:** Electrical connectors, marine hardware, specialty fasteners.
- **Best fit when:** Applications requiring conductivity or resistance to saltwater corrosion.
**7508.90 – Nickel**
- **Defining trait:** High corrosion and heat resistance; used in extreme environments.
- **Typical examples:** Aerospace components, chemical processing equipment.
- **Best fit when:** Exposure to high temperatures or corrosive chemicals.
**7616.10 – Aluminium**
- **Defining trait:** Lightweight with moderate strength; naturally corrosion-resistant.
- **Typical examples:** Aircraft parts, automotive trim, outdoor fixtures.
- **Best fit when:** Weight reduction is critical and loads are moderate.
**7907.00 – Zinc**
- **Defining trait:** Often used as a coating (e.g., galvanized), not typically for structural fasteners.
- **Typical examples:** Galvanized bolts, decorative or low-stress applications.
- **Best fit when:** Corrosion protection via plating; not intended for high strength.
**8101.99 – Tungsten**
- **Defining trait:** Extremely hard and dense; used in specialized high-wear applications.
- **Typical examples:** High-stress tooling, aerospace or military fasteners.
- **Best fit when:** Exceptional hardness or wear resistance needed.
**8102.99 – Molybdenum**
- **Defining trait:** High melting point and strength at elevated temperatures.
- **Typical examples:** High-temp industrial equipment, furnace components.
- **Best fit when:** Operating in extreme heat (e.g., above 500°C).
**8104.90 – Magnesium**
- **Defining trait:** Very lightweight but less strong; prone to corrosion.
- **Typical examples:** Aerospace or automotive parts where weight is critical.
- **Best fit when:** Weight savings outweigh strength and durability needs.
**8108.90 – Titanium**
- **Defining trait:** Excellent strength-to-weight ratio and high corrosion resistance.
- **Typical examples:** Aircraft, medical implants, marine hardware.
- **Best fit when:** High performance with light weight and long-term durability.
## Key differences
| Material | Strength | Weight | Corrosion Resistance | Heat Resistance |
|----------------|----------|--------|------------------------|------------------|
| Iron/Steel | Very High | Medium | Moderate | Low |
| Copper | Medium | Medium | High | Low |
| Nickel | High | Medium | Very High | High |
| Aluminium | Medium | Low | High | Medium |
| Zinc | Low | Medium | Moderate (coated) | Low |
| Tungsten | Very High| High | High | Very High |
| Molybdenum | High | Medium | Moderate | Very High |
| Magnesium | Low | Very Low| Low | Low |
| Titanium | High | Low | Very High | High |
## How to choose
- Is strength the top priority? → 7318.15 or 8101.99
- Is weight reduction critical? → 7616.10 or 8108.90
- Is it exposed to saltwater or chemicals? → 7415.33 or 7508.90
- Is it used in high heat (e.g., engines, furnaces)? → 8102.99 or 8101.99
## Overlaps & pitfalls
- Zinc (7907.00) is often a coating, not a structural material—avoid if load-bearing.
- Titanium and nickel both offer high corrosion resistance but differ in weight and cost.
- Tungsten and molybdenum are niche; their use depends on extreme heat or wear.
- No single trait dominates—choose based on the product’s **main function** (e.g., strength, weight, environment)