By Coating

Neodymium Magnets (NdFeB) By Coating

Neodymium magnets are also known as Neodymium-Iron-Boron or Nd-Fe-B or NIB super magnets since they are composed of these elements. The chemical composition is Nd2Fe14B. These magnets are extremely strong for their small size and are metallic in appearance.
Attributes Of Neodymium Magnets
-There are several attributes of Neodymium magnets that differentiate them from other magnets.
-Neodymium magnets are very strong permanent magnets. In fact they are the strongest of all rare earth magnets and also the strongest permanent magnets that exist today.
-Neodymium magnets have a very high resistance to demagnetization. This makes them very useful in many different kinds of industrial applications.
-Even small sized Neodymium magnets have a very high energy. This makes them easily portable from one place to another.
-They are good in ambient temperature.
-Another major attribute of Neodymium magnets that has added to their popularity is the affordability factor. Neodymium magnets, unlike previous high strength magnets like tiny cobalt-samarium magnets, are priced very low and can be afforded by educators and experimenters on their limited budgets.
-Neodymium magnets are very corrosive and hence have to be handled carefully. It is best to coat them for long-term maximum energy output and usage.
-Neodymium magnets have a low working temperature for heat applications and can catch fire at high temperatures.

Neodymium Magnet Coatings:
Titanium (Ti)
Tin (Sn)
Silver (Ag)
Gold (Au)
Zinc (Zn)
Epoxy
Nickel (Ni)
Nickel-Copper-Nickel (Ni-Cu-Ni)
Titanium Nitride (TiN)
Parylene C
Everlube
Chrome
PTFE (also known as “Teflon”; white, black, gray, silvery)
Ni-Cu-Ni plus Epoxy
Ni-Cu-Ni plus Rubber
Zn plus Rubber
Ni-Cu-Ni plus Parylene C
Ni-Cu-Ni plus PTFE
Tin (Sn) plus Parylene C
Zinc Chromate
Phosphate Passivation

Sintered Neodymium Magnet By General Coating / Palting

Double-ni-neodymium-magnet zn-neodymium-magnet epoxy-neodymium-magnet color-zinc-neodymium-magnet
 Nickel-Copper-Nickel (Ni-Cu-Ni)

  • Most common coating on magnets
  • Actually 3 layers, nickel-copper-nickel
  • Protection of the magnet from corrosion in ambient air
  • Not a protective coating from humidity, water, or salt water
  • Light protection of the magnet from chipping
  • A decorative finish
  • Shiny metallic gray finish
  • Thickness: 12-25 microns
  • Cost: Low
  • Max working Temp: Approximately 200o C
  • Gluing nickel coated magnets onto steel or plastic should be done with glue or epoxies specifically designed for magnets.
  • Main Industries: motors, medical devices (outside of body), sensors, automotive, holding, generators, pumps, thin film deposition.  Used in almost all industries
 Zinc (Zn)

  • Good adhesion when glued onto steel with a glue or epoxy specifically rated for magnets
  • Protection of the magnet from corrosion in ambient air
  • Slight protection from humidity, water, or salt water, but not consider a good choice if magnet is in moisture or fluids
  • Thickness of coating is thin, so less air gap between magnet and steel
  • Dull gray finish
  • Thickness: 4-8 micron
  • Cost: Low
  • Max working Temp: Approximately 120o C
  • Main Industries: any application where low temp, low coating cost and little protective barrier is required.
 Black Epoxy (EP)

Gray Epoxy (EP)

  • Epoxy coating is excellent as a barrier for salt air and salt water
  • Can scratch easily, must be handled carefully during assembly
  • Very good adhesion to steel with magnet rated glue
  • Mainly colored in black, however, can be colored in white
  • Thickness: 15-30 microns
  • Cost: Medium
  • Max working Temp: Approximately 200o C
  • Gluing nickel coated magnets onto steel or plastic should be done with glue or epoxies specifically designed for magnets.
  • Main Industries: Marine, motor, sensors, consumer products, automotive
 Color Zinc (Cr+Zn)

  • Good adhesion when glued onto steel with a glue or epoxy specifically rated for magnets
  • Protection of the magnet from corrosion in ambient air
  • Slight protection from humidity, water, or salt water, but not consider a good choice if magnet is in moisture or fluids
  • Thickness of coating is thin, so less air gap between magnet and steel
  • Dull gray finish
  • Thickness: 4-8 micron
  • Cost: Low
  • Max working Temp: Approximately 120o C
  • Main Industries: any application where low temp, low coating cost and little protective barrier is required.
golden-neodymium-magnet Copper-neodymium-magnet Chrome-neodymium-magnet Teflon-neodymium-magnet
Gold (Au)

  • FDA approved medical coating for in-body use
  • Has an undercoating of Ni-Cu-Ni
  • Protection of the magnet from corrosion in ambient air
  • Slight protection from humidity, water, or salt water. The thickness of the gold is very thin, so performance in salt spray tests will ultimately show failure of the coating.  Making the coating thicker will help, but gold is intended to be thin.
  • Gold finish
  • Thickness of gold layer: 0.3-0.6 micron
  • Cost: High
  • Max working Temp: Approximately 200o C
  • Main Industries: medical (in and out of body applications), jewelry, decorative uses.
 Copper (Cu)

  • Mostly used as a decorative coating
  • Protection of the magnet from corrosion in ambient air, but is less then nickel
  • Can rub off over time
  • Not a protective coating from humidity, water, or salt water
  • Copper finish
  • Thickness: 8-10 microns
  • Cost: Medium
  • Max working Temp: Approximately 200o C
  • Main Industries: Decorative
 Chrome (Cr)

  • Mostly used as a decorative coating
  • Protection of the magnet from corrosion in ambient air, but is less then nickel
  • Not a protective coating from humidity, water, or salt water
  • Chrome finish, dull metallic gray color
  • Thickness: 12-15 microns
  • Cost: Low – Medium
  • Max working Temp: Approximately 200o C
  • Main Industries: Jewelry, decorative, cosmetic, consumer products 
 PTFE (Teflon)

  • Requires molds and tooling
  • Excellent protection to magnet against breakage, impact, and corrosion
  • Available on magnets that are medium to larger in size. Small magnets cannot be molded, but can be sprayed (see Spray PTFE – Teflon)
  • Provides a protective coating from humidity, fluids and AutoClave
  • Color of PTFE is white
  • Thickness: 0.5-1 mm
  • Cost: molds & tooling are required, and cost is dependent upon complexity of each.  Cost / pc will decrease quickly with large quantities
  • Max working Temp: Approximately 250o C
  • Gluing PTFE magnets onto steel or plastic has very poor adhesion. A mechanical hold is recommended
  • Main Industries: Predominantly medical and food industries.
Phosphate-neodymium-magnet Parylene-neodymium-magnet Titanium-neodymium-magnet Silver-neodymium-magnet
Phosphate Passivation

  • Approved as a Food-grade coating
  • Requires tooling
  • Excellent protection to magnet against corrosion
  • Unlike molded PTFE, smaller magnets can be sprayed as well as larger magnets
  • Provides a protective coating from humidity and fluids
  • Can scratch, so proper handling is required
  • Color can be white or black
  • Thickness: 0.1 – 0.5 mm
  • Cost: Medium
  • Max working Temp: Approximately 200o C
  • Gluing PTFE magnets onto steel or plastic has very poor adhesion. A mechanical hold is recommended
  • Main Industries: Predominantly medical and food industries.
 Parylene

  • FDA approved medical coating for in-body use
  • Protection of the magnet from corrosion in ambient air
  • Slight protection from humidity, water, or salt water. Parylene will slowly fail in salt water, so an undercoating may be required.
  • Transparent finish
  • Thickness: 3-7 micron
  • Cost: Quantity Dependent.  Done in batches, so the higher the quantity, the lower the cost / pc.
  • Max working Temp: Approximately 150o C
  • Main Industries: medical (in body applications), and any product that needs a thin coating
 Titanium (Ti-Tin)

  • FDA approved medical coating for in-body use
  • Hard coating that has a very strong bond to the magnet
  • Resilient to most chemicals and environmentally friendly
  • Protection from humidity and fluids
  • Finished color is a metallic gold with a smooth surface
  • Thickness of: 2-3 microns
  • Cost: Medium
  • Max working Temp: Approximately 500o C
  • Main Industries: Medical 
 Silver (Ag)

  • Mostly used as a decorative coating
  • Protection of the magnet from corrosion in ambient air, but is less then nickel
  • Soft metal, so can scratch easily
  • Silver finish
  • Thickness: 12-15 microns
  • Cost: Low – Medium
  • Max working Temp: Approximately 200o C
  • Main Industries: Jewelry, decorative, cosmetic, consumer products