Magnetics Business & Technology - May/June 2019 - 8

FEATURE ARTICLE

Tech Tips: Adhesive Fundamentals for Common Magnet Bonding Applications
By Simla Ay
Hernon Manufacturing, Inc.

There are many magnet types varying in cost, corrosion resistance, temperature tolerance and field strength. These properties
result from different shapes and constituents with common types
of magnets including neodymium, samarium cobalt and ferrite/
ceramic magnets. The type of adhesive recommended for each
depends on the intended use, the material coating the surface
of the magnet, if any, and the material to which the magnet is
bonded.
Many neodymium magnets have a nickel coating and epoxies are
best at bonding with the nickel plating of the magnet. Samarium
cobalt magnets do not require coating and can be used for higher
temperature applications up to 350 degrees C. These high temperatures may require specialized ceramic adhesives to tolerate
the heat. Ferrite or ceramic magnets are common due to their low
cost and don't require coating. Many common types of structural
adhesives can be used with ferrite magnets.
As a manufacturer of high-performance adhesives, Hernon
Manufacturing regularly receives requests to advise on magnet
bonding applications. This article addresses some of the most
common magnet bonding applications that we encounter and important aspects of their adhesive requirements.

Magnetic drain plugs are mainly used to trap and remove microscopic metal particles from engine lubricating oil. The drain plug
protects engines and industrial equipment from metal particles by
pulling them from the oil. The magnet in these drain plugs is typically a tight fitted cylinder attached to a threaded cap as pictured.
The family of adhesive required for this application is a retaining
compound. As with many magnet applications a drain plug is often found in a high vibration environment with occasional impacts
from motion. Heat cycling can also affect the bond as the engine
warms and cools. Another key factor is oil exposure. Any adhesive for magnetic drain plugs must tolerate long term exposure to
a variety of engine fluids.
Magnets play a key role in audio speaker functionality. For the
speaker to work properly, a strong bond needs to be formed between the magnet and poll piece as well as magnet and base
plate. This provides the magnetic structure for the voice coil to
move through creating vibrations and moving the speaker cone

Magnetics Business & Technology * May/June 2019

to make sound waves. Vibrations can play havoc with mechanical
fasteners while the flexibility of adhesive bonds protects speakers from damage by strong vibrations.
Magnets in electric motors are bonded in place with adhesives for
several reasons. Magnets are brittle and susceptible to fracturing. Adhesives disperse stress across the entire bonded surface,
reduction stress focus points and mitigating fracturing risk. Due to
the high vibration environment, any space between components
will allow for vibration and increased noise and wear on parts.
This is especially important for coated wires which can be delaminated by the vibration resulting in a short. Adhesives minimize
noise and vibration due to their visco-elastic properties. Adhesives also bond to a variety of substrates including metal and
plastic materials and produce strong bonds very quickly making
them an ideal choice for large scale manufacturing.

In summary, the variety of magnet bonding applications is as varied as manufacturing itself. Each application offers unique challenges from different substrates to thermal changes, chemical
exposure, vibration and more. Adhesive manufacturers can help
you select from the thousands of adhesives available to find the
best match for your specific application.

About the Author

Simla Ay is a technical writer with Hernon Manufacturing, Inc.
of Sanford, FL. Hernon manufactures adhesives, sealants and
processing solutions including precision dispensing equipment
and customized formulations. For more information, see www.
hernon.com.
www.MagneticsMag.com

http://www.hernon.com http://www.hernon.com http://www.MagneticsMag.com

Magnetics Business & Technology - May/June 2019

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