The Characteristics of Magnet Coatings

March 02, 2018

Which Magnet Coating Is Right for Your Application?

By: Michael Brand, President, SM Magnetics

The list of coatings on magnets is long.  The correct coating for your application will be determined by many factors, such as environment, temperature, durability and government requirements, such as FDA approved coatings.  Below is a list of the different coatings and their characteristics to help you weave through the maze of options. As you review the list, remember to thoroughly consider the parameters of your application. If you would like to view/download our PDF Coatings Chart click the link. 

View/Buy Special magnet coatings collection on SuperMagnetMan

Nickel

  • 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: 15-25 um
  • 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

Click Here to View / Buy Nickel Plated Magnets 

 

Black Nickel

  • Three layers, nickel-copper-nickel, plus an extra process to get the black nickel finish
  • 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 black/gray finish
  • Thickness: 12-25 um
  • 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.             

 

Gold

  • 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: .1- 1um
  • Cost: High
  • Max working Temp: Approximately 200o C
  • Melting Point: 1,000
  • Main Industries: medical (in and out of body applications), jewelry, decorative uses.           

Click Here to View / Buy Gold Plated Magnets 

 

Zinc

  • 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
  • White-blue, Black
  • Thickness: 4-10 um
  • Cost: Low
  • Max working Temp: Approximately 120o C
  • Main Industries: any application where low temp, low coating cost and little protective barrier is required.

 

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 of gold layer: 1-70 um
  • Cost: Quantity Dependent.  Done in batches, so the higher the quantity, the lower the cost / pc.
  • Max working Temp: Approximately 120-305o C
  • Main Industries: medical (in body applications), and any product that needs a thin coating

Click Here to View / Buy Parylene Coated Magnets

 

Epoxy

  • 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 um
  • 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.

Click Here to View / Buy Black Epoxy Coated Magnets

 

Injection Molding / Plastic

  • 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 coated in plastic
  • A protective coating from humidity, water, or salt water
  • Color of plastic can be tinted to almost any color requested
  • Thickness: 1-2 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: Dependent upon the type of ABS plastic selected
  • Gluing plastic coated magnets onto steel or plastic should be done with glue or epoxies specifically designed for magnets and the adhesion should be excellent
  • Main Industries: medical, educational, consumer products, and applications where cleaning the plastic coated magnet may include chemicals or fluids.

 

Molded 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: 1.5-3 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.

Click Here to View / Buy PTFE Coated Magnets

 

Spray PTFE (Teflon)

  • 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: 20-25 mm
  • Cost: Medium
  • 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.

 

Rubber

  • Requires molds and tooling
  • Excellent protection to magnet against breakage, impact, and corrosion
  • Provides excellent friction from sliding against steel
  • Available on magnets that are medium to larger in size. Small magnets cannot be rubber coated
  • Color of Rubber can vary, however black is the standard color and colors other than black may cost more
  • Thickness: -0.5mm
  • 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 135o C
  • A mechanical hold is recommended instead of gluing rubber coated magnets to steel or plastic
  • Main Industries: Holding applications and industrial use

Click Here to View / Buy Rubber Coated Magnets

 

Rhodium

  • Very strong coating, provides excellent resistance to scratches, and tarnish.
  • Protection of the magnet from corrosion
  • White reflective finish
  • Appearance is very decorative
  • Thickness of gold layer: 1-5 um
  • Cost: High
  • Max working Temp: Approximately 200o C
  • Melting point: 2,000
  • Main Industries: Jewelry, medical, and automotive 

 

Titanium Nitride (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 gold layer: 3-6um
  • Cost: Medium
  • Max working Temp: Approximately 500o C
  • Melting point: 3,000
  • Main Industries: Medical 

 

Copper

  • 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: 10-20um
  • Cost: Medium
  • Max working Temp: Approximately 200o C
  • Main Industries: Decorative

Click Here to View / Buy Copper Plated Magnets

 

Chrome

  • 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 um
  • Cost: Low - Medium
  • Max working Temp: Approximately 200o C
  • Main Industries: Jewelry, decorative, cosmetic, consumer products 

Click Here to View / Buy Chrome Plated Magnets

 

Silver

  • 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: 10-20um
  • Cost: Low - Medium
  • Max working Temp: Approximately 200o C
  • Main Industries: Jewelry, decorative, cosmetic, consumer products

Click Here to View / Buy Silver Plated Magnets

About SM Magnetics: SM Magnetics is privately owned company, providing assistance with permanent magnets, magnetic design & optimization, engineering support, and production.  SuperMagnetMan is the online retail division of SM Magnetics offering neodymium magnets and other materials.





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