How to Protect Magnets from Corrosion

Most magnets contain some amount of iron. In fact, the strongest permanent magnet material, Neodymium, is more than 60% iron. Unfortunately, this iron can make magnets susceptible to corrosion when uncoated. For example, Neodymium magnets may rust in humid conditions, inhibiting their magnetic performance over time.

Corrosion ProtectionMagnets should have rounded corners with 0.015” to 0.020” radius to facilitate coating optimization.

To prevent this loss of functionality and strength, we recommend a multi-layer plating of nickel, copper, and nickel (Ni-Cu-Ni). This coating offers a high level of corrosion protection for the value.

In addition, it has a maximum working temperature of approximately 220-240°C (higher than the magnet’s operating temperature). Ni-Cu-Ni coating is used in many applications, including sensors, motors, generators, medical devices, pumps, and more.

Other coatings with different properties make them more or less suited to a particular working environment. The table below outlines these coatings/platings and their respective performance under commonly seen conditions. Our applications experts can also answer any questions you might have about the right plating or coating for your specific needs.


Other reasons to coat magnets

Samarium Cobalt

Samarium Cobalt magnets are inherently corrosion-resistant, so coating for increased corrosion protection is not common. However, smaller SmCo magnets are sometimes coated to prevent chipping or cracking. Likewise, un-ground sintered SmCo material can have rough surfaces, so a coating or plating might make sense to make it easier to clean these magnets if necessary. The most common coating is Nickel (not Ni-Cu-Ni) although others are available.


Like Samarium Cobalt, Alnico is also intrinsically corrosion resistant. However, it does contain some free iron, and, over time, surface corrosion may propagate. Although not commonly required, red epoxy paint can prevent this corrosion and is most often seen on horseshoe magnets.


Made from iron oxides, Ceramic magnets are the most naturally corrosion-resistant sintered magnets available. As a result, exposure to water, saltwater, solvents, oils, and even weak acids will have a negligible impact on their performance. Coatings are most commonly applied to Ceramic magnets for cosmetic reasons or to help prevent the transfer of ferrite dust. Because Ceramic magnets are non-conductive, they can’t be electroplated like NdFeB, SmCo, and Alnico materials, but there are many electroless coatings available. Common surface treatments for Ceramic ferrite magnets include paint, powder coat, parylene, phenolic resin, Teflon, silicone, and EPDM rubber.

Contact us for more details about coating options!

Coating Color Approx. Thickness (µ m) Salt fog Salt Water Humidity Water Abrasion Resistance Relative Cost
Nickel Copper Nickel Bright 10-20 Poor Poor Fair Fair Excellent Lowest
Zinc Blue White 8-10 Fair Poor Good Fair Good Low
Zinc W/ Chromate Multi-color 8-10 Fair Poor Good Fair Good Low
Nickel Tin Silver White 12 Good Fair Good Good Good Medium
Nickel Silver Silver 10-15 Good Fair Excellent Good Fair High
Nickel Gold Gold 10-15 Good Fair Excellent Good Fair High
Epoxy Black, Grey 15-30 Excellent Excellent Excellent Good Poor Medium
Everlube Gold Metallic 8-15 Good Good Excellent Excellent Fair High
Nickel Copper Everlube Gold Metallic 15-25 Excellent Excellent Excellent Excellent Good High
Parylene C Clear 10 – 25 Excellent Excellent Excellent Excellent Poor Highest
Phenolic Resin Black 13 Excellent Excellent Excellent Excellent Excellent High
AL (PVD) Silver, Grey 2 Poor Poor Fair Poor Excellent Highest