Neodymium Magnet Plating & Coating

Neodymium magnets are much more susceptible to corrosion than Ceramic, Samarium Cobalt and Alnico, and would need to be coated and protected, particularly in harsh settings. They can be easily oxidized if exposed to air and moisture in atmosphere, and would become structurally vulnerable leading to breakage. To prevent this, there are several types of coatings available for custom magnets and selection should be dependable on their tolerance to the operating environment, especially the ones with high acidity and humidity. To reinforce their durability and resistance to abrasion, the coatings are often multi-layered. However, when their coating wears down or chips off, the Neodymium magnets cannot be re-plated and the exposed area will rust, breaks down into powder and lose their magnetic performance. Let’s take a look at the variety of surface finishes available in the market.

Neodymium Magnet Plating & Coating

Neodymium Magnet Plating & Coating

Nickel (Ni-Cu-Ni): Most commonly used, multi-layer plating, ~12-18 microns, shiny metallic color
Pros: durable, suitable for indoor use and can withstand moderate amount of abrasion and humidity, low cost to performance ratio
Cons: cannot resist acidity or salty environment
Zinc (Zn): turns white creating a durable layer of protection when exposed to corrosiveness, single layer, ~8-10 microns, shiny silver metallic color
Pros: high resistance against abrasion and humidity, can withstand moderate acidity and salty environment, low cost to performance ratio
Cons: cannot survive in salt water
Gold (Ni-Cu-Ni-Au) or Silver (Ni-Cu-Ni-Ag): gold or silver layer thickness is ~0.05 microns, entire layer is ~12-18 microns, shiny golden or silver metallic color
Pros: similar features as Ni-Cu-Ni but more chemically inert
Cons: high cost to performance ratio making this expensive fourth layer
Epoxy (Ni-Cu-Ni-Epoxy or Epoxy alone): ~10-12 microns, black color
Pros: Non-corrosive, good for outdoor application
Cons: not resistant to impact, prone to scratch, can be easily damaged to expose the magnet, medium cost to performance ratio
Chrome (Ni-Cu-Ni-Cr): ~18 microns, dull grey metallic color
Pros: resilient against rubbing
Cons: cannot resist acidity or salty environment
Titanium Nitride (TiN): ~12-15 microns, dull golden metallic
Pros: good chemical stability and corrosion resistance, frequently used dental and medical applications
Cons: high cost to performance ratio, not suitable for acidic solution
Teflon: ~15-25 microns, light grey color
Pros: waterproof or repel moisture, resilient to scratch
Cons: medium cost to performance ratio
Plastic or Rubber: >250 microns, various color, need to create mold for plastic shell
Pros: highly corrosion resistant, increase friction
Cons: medium cost to performance ratio, weaken magnetic pull strengths
Naked:Black/grey must be isolated from air or oxygen and should be vacuum packed.
Besides the above choices, there are a few other commonly requested platings, like Tin (Sn), Titanium (Ti), Parylene, Zinc Chromate and Phosphate Passivation.

During plating process, magnets must be thoroughly cleaned and dried to avoid moisture trapped in between magnets and coating. Besides properly preparing the magnet material and carrying out the plating process, chamfering magnets’ edges are also crucial for successful and durable plating. Every application can be complex with multiple elements to be considered. It is recommended to test a small number of magnets first to verify their compatibility with the application and effectiveness of their coating, especially in prolonged exposure to harsh chemicals and abrasion in a controlled environment. Our Neodymium magnet assemblies mostly use Ni-Cu-Ni plating with additional rubber cover or mild steel cups.

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