## Common ground
All options are self-locking nuts made from different metallic materials.
## Options at a glance
**7318.16 – Iron or steel**
- **Defining trait:** Highest strength and durability; standard for general industrial use.
- **Typical examples:** Machine bolts, automotive fasteners, structural assemblies.
- **Best fit when:** High load-bearing capacity and corrosion resistance (with coating) are needed.
**7415.33 – Copper**
- **Defining trait:** Excellent electrical conductivity and non-magnetic properties.
- **Typical examples:** Electrical connectors, marine applications, high-frequency equipment.
- **Best fit when:** Conductivity or non-magnetic use is essential.
**7508.90 – Nickel**
- **Defining trait:** High corrosion and heat resistance; often used in harsh environments.
- **Typical examples:** Aerospace components, chemical processing equipment.
- **Best fit when:** Resistance to extreme temperatures or corrosive chemicals is required.
**7616.10 – Aluminium**
- **Defining trait:** Lightweight with moderate strength; prone to galling.
- **Typical examples:** Aircraft parts, consumer electronics, lightweight machinery.
- **Best fit when:** Weight reduction is critical and loads are low to medium.
**7907.00 – Zinc**
- **Defining trait:** Low cost and good corrosion resistance (often via galvanization).
- **Typical examples:** Outdoor fixtures, fencing, low-stress fasteners.
- **Best fit when:** Budget constraints and moderate environmental exposure.
**8101.99 – Tungsten**
- **Defining trait:** Extremely high melting point and hardness; rare in standard nuts.
- **Typical examples:** High-temperature industrial tools, specialized aerospace parts.
- **Best fit when:** Extreme heat or wear resistance is needed (not common).
**8102.99 – Molybdenum**
- **Defining trait:** High thermal stability and strength at elevated temperatures.
- **Typical examples:** Rocket engines, furnace components.
- **Best fit when:** Operating in very high-temperature environments.
**8104.90 – Magnesium**
- **Defining trait:** Lightest metal; highly reactive and flammable.
- **Typical examples:** Racing car parts, aerospace (rare due to safety risks).
- **Best fit when:** Weight savings outweigh fire risk concerns.
**8108.90 – Titanium**
- **Defining trait:** Excellent strength-to-weight ratio and 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 | Temperature Tolerance |
|----------------|----------|--------|------------------------|------------------------|
| Iron/Steel | Very High | Medium | Moderate (with coating) | Medium |
| Copper | Low | Medium | Good | Low |
| Nickel | High | Medium | Very High | Very High |
| Aluminium | Medium | Low | Moderate | Low |
| Zinc | Low | Medium | Good (via coating) | Low |
| Tungsten | Very High| Medium | High | Extremely High |
| Molybdenum | High | Medium | High | Extremely High |
| Magnesium | Low | Very Low | Poor | Low |
| Titanium | High | Low | Very High | High |
## How to choose
- Is strength and durability the top priority? → 7318.16
- Does the application require electrical conductivity or non-magnetism? → 7415.33
- Is the environment corrosive or very hot? → 7508.90 or 8102.99
- Is weight reduction critical? → 7616.10 or 8108.90
- Is cost the main concern? → 7907.00
## Overlaps & pitfalls
A nut may qualify for multiple codes if it combines traits (e.g., titanium is strong, light, and corrosion-resistant). However, **the material is the defining factor**—choose based on the primary metal used. Avoid confusion: "self-locking" applies to all; only material matters here