Platings/Coatings/Adhesives

[Q] Why are most neodymium magnets plated or coated?
[A] Neodymium magnets are composed mainly of Neodymium, Iron, and Boron. If neodymium magnets are not plated, the iron in the material will oxidize very easily if exposed to moisture. Even normal humidity will rust the iron over time. To protect the iron from exposure to moisture, most neodymium magnets are plated or coated.
[Q] What is the difference between the different platings and coatings?
[A] Choosing different coatings does not affect the magnetic strength or performance of the magnet, except for our Plastic and Rubber Coated Magnets. The preferred coating is dictated by preference or intended application.
Nickel is the most common choice for plating neodymium magnets. It is actually a triple plating of nickel-copper-nickel. It has a shiny silver finish and has good resistance to corrosion in many applications. It is not waterproof.
Black nickel has a shiny appearance in a charcoal or gunmetal color. A black dye is added to the final nickel plating process of the triple plating of nickel-copper-black nickel. NOTE: It does not appear completely black like epoxy coatings. It is also still shiny, much like plain nickel plated magnets.
Zinc has a dull gray/bluish finish, that is more susceptible to corrosion than nickel. Zinc can leave a black residue on hands and other items.
Epoxy is basically a plastic coating that is more corrosion resistant as long as the coating is intact. It is easily scratched. From our experience, it is the least durable of the available coatings.
Gold plating is applied over the top of standard nickel plating. Gold plated magnets have the same characteristics as nickel plated ones, but with a gold finish.
[Q] Can I paint over the nickel plating?
[A] Yes, you can use any paint formulated for use on metal surfaces. Spray-on paint seems to work best. Roughing the surface first can help improve paint adhesion to the smooth, nickel plated surface. Sandblasting or beadblasting works, as well as an etching primer.
[Q] What is the thickness of the nickel (Ni-Cu-Ni) plating?
[A] The nickel plating is actually triple plating of nickel-copper-nickel. The layers are Ni: 5-6µm, Cu: 7-8µm, Ni: 5-6µm, for a total thickness of 17-20µm.
[Q] Do you stock any unplated magnets?
[A] As mentioned above, the iron in the NdFeB material will oxidize if it is exposed to moisture. For this reason, we do not stock any unplated magnets. We can supply unplated magnets as custom order items.
[Q] What is the best adhesive to use with your magnets?
[A] Using Loctite 39205 (an acrylic adhesive) with Loctite 7380 activator to the nickel-plating. Loctite representative recommend Loctite 3032 (a 2-part acrylic adhesive) with Loctite primer 770. For more commonly found adhesives, we have also had great results using many kinds of epoxy, often sold as “5-minute” epoxy. “Liquid Nails” and “Gorilla Glue” can also work well, and are available in most hardware and home supply stores. It does help to scratch the surface of the plating lightly with sandpaper or other abrasive prior to applying the adhesive.
[Q] I noticed that the plastic- and rubber-coated magnets have a lower pull force than nickel-plated magnets of the same size. Does the plastic/rubber weaken the magnet?
[A] These materials don’t “weaken” the magnet, but the volume of magnet material is reduced to allow room for the coatings, which reduces the pull force. The layer of plastic or rubber also creates distance between the magnet and metal surface which also reduces the pull force.
[Q] How can I protect my magnets from damage due to impact?
[A] Wrapping magnets with a few layers of electrical tape protects them from most damage caused by collisions with other magnets and hard surfaces. Another great way to protect your magnets from damage and the elements is to coat them with rubberized coating.


Post time: Dec-25-2019
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