Are Compression Bonded Magnets Corrosion-Resistant for Automotive Use?

Compression bonded magnets are highly resistant to corrosion when properly coated, making them an excellent and reliable choice for a wide range of automotive applications. The key lies in applying a protective barrier over the magnet's surface.

What You'll Learn

• Why corrosion is a critical factor for magnets used in vehicles.
• The composition of compression bonded magnets and their inherent properties.
• How protective coatings provide robust corrosion resistance.
• The specific automotive applications where these magnets excel.
• The advantages of sourcing a complete, coated magnet solution from a single domestic supplier.
  
  

The Challenge: Why Corrosion is a Critical Concern in Automotive Magnets

The environment inside a modern vehicle is surprisingly harsh. Components are routinely exposed to a wide range of temperatures, humidity, condensation, and, in many climates, corrosive road salt.

For any permanent magnet, corrosion is a significant threat. Oxidation can degrade the magnetic material, leading to:

• Reduced Magnetic Performance: A corroded magnet loses its strength, causing motors to become inefficient or sensors to lose accuracy.
• Mechanical Failure: The structural integrity of the magnet can be compromised, leading to cracks or complete component failure.
• System Malfunction: In critical systems like power window actuators or seat adjustment motors, a failed magnet can mean a loss of functionality.

Therefore, any magnet intended for automotive use must have a reliable defense against corrosion to ensure the vehicle's longevity and safety.

Understanding Compression Bonded Magnets and Their Composition

To understand their corrosion resistance, we first need to look at what compression bonded magnets are made of. They are produced by mixing a fine powder of a powerful Rare Earth magnetic material, Neodymium-Iron-Boron (NdFeB), with a resin binder (like epoxy) and pressing it into a precise shape in a mold.

While the NdFeB material offers exceptional magnetic strength, it is inherently susceptible to oxidation, or rust, when exposed to moisture. This is where the manufacturing process and secondary treatments become critical.

The Solution: How Coatings Make Compression Bonded Magnets Corrosion-Resistant

The corrosion resistance of a compression bonded magnet is achieved through a two-layer defense system: the binder and a secondary protective coating.

The Role of the Resin Binder

During manufacturing, the resin binder encapsulates the individual particles of NdFeB powder. This process provides a foundational level of protection by isolating many of the magnetic particles from direct contact with the atmosphere. However, for the demanding conditions in automotive applications, this alone is not enough.

Essential Protective Coatings

For robust, long-term protection, a secondary coating is applied to the finished magnet. This outer layer acts as an impermeable barrier, completely sealing the magnet from corrosive elements as well as physically harsh environments.

Common and effective coatings for Compression Bonded Magnets include:

• Epoxy: This is a very common choice, offering excellent resistance to humidity, salt spray, and various chemicals. It provides a durable, paint-like finish.
• Parylene: A high-performance polymer coating that is applied as a gas, Parylene conforms perfectly to the magnet's shape, creating an ultra-thin, pinhole-free barrier that provides superior protection against moisture and chemicals.

By selecting the appropriate coating, Compression Bonded Magnets can be engineered to meet and exceed the stringent durability requirements of the automotive industry.

Common Automotive Applications for Coated Compression Bonded Magnets

The combination of design flexibility, consistent magnetic performance, and excellent corrosion resistance makes Compression Bonded Magnets ideal for numerous automotive systems.

• Fractional Horsepower Motors: These magnets are a perfect fit for small motors that power convenience features. Their ability to be molded into complex shapes, like thin-walled rings, is a major advantage.
  • Specific Uses: Power seat adjustment motors, sunroof controls, and automatic window actuators. In these applications, the coated magnet ensures reliable operation for the vehicle's entire lifespan.
• Sensors and Encoders: Modern cars rely on dozens of sensors for everything from engine timing to stability control. Compression Bonded Magnets are used in rotary encoders and motion sensors where their precise, multi-pole magnetization patterns are essential.
  • Specific Uses: Wheel speed sensors, steering wheel angle sensors, and throttle position sensors. Corrosion resistance is non-negotiable here, as any degradation would compromise sensor accuracy and vehicle safety.
    
    

Sourcing a Reliable Solution: The Importance of a Domestic Supply Chain

For automotive manufacturers, quality control and supply chain reliability are paramount. Sourcing magnets from a supplier that manages the entire production process—from powder formulation to pressing, coating, and magnetization—is a significant advantage.

Magnet Applications, a division of Bunting, is the only U.S.-based manufacturer that offers a complete, end-to-end domestic supply chain for Compression Bonded Magnets. This unique capability ensures:

• Total Quality Control: Every step, including the critical coating process, is handled in-house at their DuBois, PA facility.
• Automotive-Grade Compliance: They can provide full Production Part Approval Process (PPAP) documentation, a standard requirement in the automotive industry.
• Supply Chain Security: A 100% U.S.-based pipeline eliminates the risks associated with international logistics and trade restrictions.
  
  

The Final Verdict

So, are compression bonded magnets resistant to corrosion for automotive applications?

The answer is a resounding yes, provided they are manufactured with the correct protective coating. The combination of an internal resin binder and a robust external coating like epoxy or Parylene creates a durable, reliable component that can withstand the harsh automotive environment. Their unique blend of performance, design flexibility, and proven longevity makes Compression Bonded Magnets an intelligent choice for engineers designing the next generation of vehicles.

Frequently Asked Questions

No, the magnetic material they are made from, Neodymium-Iron-Boron (NdFeB), is inherently susceptible to oxidation or rust. Their corrosion resistance is achieved through a two-layer defense system: the resin binder used in manufacturing and a crucial secondary protective coating applied to the finished magnet.

They are protected by a two-layer system. The first layer is the resin binder that encapsulates the magnetic particles during manufacturing. The second, more critical layer is a robust outer coating, such as epoxy or Parylene, which acts as an impermeable barrier against moisture, road salt, and chemicals common in automotive environments.

Coated compression bonded magnets are used in numerous automotive systems. Common applications include small motors for convenience features like power seats, sunroofs, and automatic windows, as well as critical components like wheel speed sensors, steering angle sensors, and throttle position sensors where accuracy and reliability are essential.