Why Are Most Neodymium Magnets Plated or Coated?
Because bare neodymium alloy is about 64 to 68% iron and rusts quickly, even in normal humidity. A plating or coating seals out moisture, protects the brittle magnet from chipping, and gives a clean finish. Our standard is a three-layer nickel-copper-nickel (Ni-Cu-Ni) plating, which protects magnets well in dry, indoor conditions.
Why Three Layers?
Inner Nickel
About 3–7 µm. Bonds to the magnet surface and seals it.
Copper
About 5–10 µm. Fills tiny pores and evens out the surface so the outer layer seals completely.
Outer Nickel
About 5–10 µm. A hard, bright finish that resists wear and corrosion.
How Thick Is the Plating?
The full Ni-Cu-Ni plating is typically about 10–25 µm (roughly 0.0004–0.001 in) thick on each surface, and most standard parts fall around 15–20 µm. That’s thinner than a sheet of paper.
Do Listed Sizes Include the Plating?
Yes. Our listed dimensions are the finished size, with the coating included. Every surface is plated, so any dimension you measure across a magnet passes through the plating twice, once on each side. A disc’s diameter and its thickness each include about 20–50 µm (roughly 0.0008–0.002 in) of plating, usually 30–40 µm (about 0.0012–0.0016 in).
| Plating | On each surface | Across a dimension (both sides) |
|---|---|---|
| Typical range | 10–25 µm (0.0004–0.001 in) | 20–50 µm (0.0008–0.002 in) |
| Most standard parts | 15–20 µm (0.0006–0.0008 in) | 30–40 µm (0.0012–0.0016 in) |
You don’t need to add anything for the plating when you size a pocket, hole or fit. Design to the listed size and our ±0.004 Inch tolerance.
Other Coatings for Tougher Conditions
| Coating | Best for |
|---|---|
| Nickel (Ni-Cu-Ni) | Indoor, dry use (standard) |
| Black epoxy | Humidity and outdoor use |
| Plastic (ABS) | Water, salt and impact protection |
| Rubber | Scratch-free surfaces |
| Gold over nickel | Appearance |
See all coating options.