## Common ground
All options are metal washers (non-spring, non-lock) made from different metallic materials.
## Options at a glance
**7318.22 – Iron or steel**
- **Defining trait:** Made from ferrous metal with high strength and common industrial use.
- **Typical examples:** Machine bolts, automotive fasteners, structural assemblies.
- **Best fit when:** High strength, durability, and cost-effectiveness are priorities.
**7415.33 – Copper**
- **Defining trait:** Conductive and corrosion-resistant; used where electrical or thermal conductivity matters.
- **Typical examples:** Electrical connectors, plumbing joints, RF shielding.
- **Best fit when:** The washer must conduct electricity or resist oxidation in moist environments.
**7508.90 – Nickel**
- **Defining trait:** Resists corrosion and high temperatures; often used in harsh environments.
- **Typical examples:** Aerospace components, chemical processing equipment.
- **Best fit when:** Exposure to extreme heat, chemicals, or corrosive conditions.
**7616.10 – Aluminium**
- **Defining trait:** Lightweight with good corrosion resistance; non-magnetic.
- **Typical examples:** Aircraft parts, consumer electronics, marine hardware.
- **Best fit when:** Weight reduction and non-magnetic properties are key.
**7907.00 – Zinc**
- **Defining trait:** Often used as a coating or in sacrificial applications; less common as base material.
- **Typical examples:** Galvanized fasteners, corrosion protection layers.
- **Best fit when:** The washer is part of a protective coating system.
**8101.99 – Tungsten**
- **Defining trait:** Extremely dense and hard; used in high-wear or high-density applications.
- **Typical examples:** Heavy machinery, radiation shielding, precision tools.
- **Best fit when:** Exceptional hardness, density, or wear resistance is required.
**8102.99 – Molybdenum**
- **Defining trait:** High melting point and thermal stability; used in extreme heat environments.
- **Typical examples:** Furnace components, high-temperature seals.
- **Best fit when:** The washer operates under very high temperatures.
**8104.90 – Magnesium**
- **Defining trait:** Lightest structural metal; prone to corrosion unless protected.
- **Typical examples:** Aerospace and automotive lightweight parts.
- **Best fit when:** Weight is the primary concern, and protection from corrosion is managed.
**8108.90 – Titanium**
- **Defining trait:** Strong, lightweight, and highly corrosion-resistant; ideal for demanding environments.
- **Typical examples:** Medical implants, aerospace, marine engineering.
- **Best fit when:** High strength-to-weight ratio and long-term durability in aggressive environments.
## Key differences
| Material | Density | Corrosion Resistance | Strength | Temperature Stability |
|---------------|--------|-----------------------|----------|------------------------|
| Iron/Steel | Medium | Low (unless coated) | High | Medium |
| Copper | High | High | Medium | Medium |
| Nickel | High | Very High | High | Very High |
| Aluminium | Low | High | Medium | Medium |
| Zinc | Medium | Medium | Low | Low |
| Tungsten | Very High | Medium | Very High| Extremely High |
| Molybdenum | High | High | High | Extremely High |
| Magnesium | Very Low | Low (unless coated) | Low | Low |
| Titanium | Medium | Very High | High | High |
## How to choose
- Is the washer used in high-temperature or extreme environments? → 8102.99, 8101.99, 8108.90
- Does it need to conduct electricity? → 7415.33
- Is weight a critical factor? → 8104.90, 7616.10
- Is corrosion resistance the main requirement? → 7508.90, 8108.90, 7616.10
- Is it part of a protective coating system? → 7907.00
## Overlaps & pitfalls
A washer may serve multiple purposes (e.g., titanium is strong, light, and corrosion-resistant). If the product has multiple traits, prioritize based on its **main function**. No option is vague—each clearly defines a distinct material with unique properties