Why do neodymium magnets rust?

Neodymium magnets are known as the most powerful permanent magnets commercially available. They are used in thousands of products, from industrial machines and electric motors to consumer electronics and magnetic closures.

However, neodymium magnets have a characteristic that surprises many users: without protection, they can rust.

How can a modern technical material that is so strong also be susceptible to corrosion?

Neodymium is susceptible to oxidation

A neodymium magnet is not exclusively made of neodymium.

The material is produced from an alloy of:

• Neodymium (Nd)
• Iron (Fe)
• Boron (B)

This combination is known as NdFeB.

The iron present, in particular, makes the material susceptible to oxidation. When moisture and oxygen reach the surface, corrosion can occur.

This process is very similar to the rusting of ordinary steel.

Why do some magnets rust faster?

Not every environment is the same.

The risk of corrosion increases with:

• high humidity
• outdoor use
• condensation
• saltwater
• industrial environments
• damaged coatings

When moisture remains in contact with the magnet material for an extended period, the corrosion can spread beneath the protective layer.

What happens if a magnet rusts?

Rust not only affects the appearance.

When corrosion penetrates deeper into the material, the magnetic properties can also be affected.

In severe cases, the material can:

• crumble
• crack
• weaken
• partially demagnetize

Therefore, protection against corrosion is important for the lifespan of a neodymium magnet.

Why do neodymium magnets have a coating?

Almost all neodymium magnets are provided with a protective coating.

This layer forms a barrier between the magnet material and the environment.

Common coatings include:

Ni-Cu-Ni (Nickel-Copper-Nickel)

The most common finish.

This coating offers:

• good corrosion protection
• a shiny metallic appearance
• high wear resistance

Epoxy

Epoxy forms an additional protective plastic layer.

Advantages:

• better protection against moisture
• suitable for harsher conditions
• often in black

Rubber coating

Rubber protects both the magnet and the contact surface.

Widely used for:

• vehicles
• displays
• sensitive surfaces

Plastic enclosures

In some applications, the magnet is completely enclosed in plastic.

This provides maximum protection against moisture and damage.

What about gold, rose gold, and gunmetal?

Some magnets are finished with decorative coatings.

Examples include:

• gold-coloured
• rose gold
• gunmetal

These coatings are often chosen for their appearance in visible applications such as displays, interior design, luxury packaging, or design products.

The underlying magnet remains the same; the coating primarily determines the appearance and provides additional protection.

Can neodymium magnets be used outdoors?

Yes, provided the correct version is chosen.

For outdoor use, the following are usually suitable:

• epoxy coated magnets
• rubber coated magnets
• plastic-encased magnets

A standard nickel-plated magnet can function outdoors but generally has a shorter lifespan when exposed to moisture for prolonged periods.

How to extend the lifespan?

To prevent corrosion, it is advisable to:

• avoid damaging the coating
• store magnets dry
• avoid prolonged contact with water
• choose the correct coating

This way, neodymium magnets can last for decades.

Conclusion

Neodymium magnets contain iron and are therefore susceptible to corrosion when moisture and oxygen reach the material. To prevent this, almost all neodymium magnets are provided with a protective coating such as nickel, epoxy, rubber, or plastic. With the right protection, neodymium magnets can continue to function reliably for years, even in challenging environments.