Rare earth magnets or ferrite magnets, Neodymium magnets are used in various applications in the technical, industrial and medical fields. The magnet needs to be provided with surface protection against corrosion, the "coating" of the magnet.
In order to get the best performance from your magnet, regardless of its application, you should make sure it has the correct coating.
Since corrosion can be one cause of complete magnet failure, selecting a quality magnet with the correct coating and quantity is critical to the success of your application.
What is Magnet Coating
Magnet coating (also known as magnetic paints or primers) refers to the application of a protective layer on the surface of magnets to enhance their performance and durability while safeguarding them from corrosion, moisture, oxidation, and other environmental factors.
Neodymium, ferrite, and samarium-cobalt magnets, for example, can be quite brittle, so the coatings offer the magnets extra durability. Note that coatings do not impact the core magnetic properties of the magnets.
This coating process ensures that the magnets maintain their magnetic properties and resist wear and tear, making them more reliable and long-lasting in various applications. Different types of coatings, such as nickel-copper-nickel, epoxy resin, zinc, gold, tin, and copper, offer varying levels of protection based on specific application requirements and environmental conditions.
Magnet coating plays a crucial role in maximizing the efficiency and effectiveness of magnets across industries like electronics, automotive, medical, and renewable energy.
What are the Characteristics of Magnet Coating?
Corrosion Resistance: Protects magnets from moisture and harsh environments.
Environmental Protection: Shields against abrasion and ensures stable performance in various conditions.
Temperature Stability: Withstands high temperatures in extreme environments.
Adhesion: Forms a strong and uniform protective layer on the magnet's surface.
Electrical Insulation (for electrical magnets): Prevents short-circuits and ensures safe operation.
Biocompatibility (for medical applications): Safe for use in or around the human body.
Aesthetics: Provides attractive appearance with options like gold or colored coatings.
Ease of Application: Efficient and compatible with magnet manufacturing methods.
Regulatory Compliance: Meets industry standards and certifications for specific applications.
By selecting the appropriate magnet coating based on the desired characteristics and application requirements, manufacturers can ensure that the magnets perform optimally and withstand the demands of their intended environments.
Why Magnet Coating Is Important
Magnet coating is crucial as it provides vital protection to magnets. Coatings shield magnets from corrosion, harsh environments, and abrasion, ensuring their longevity and preserving their magnetic properties.
Additionally, coatings offer environmental resilience, electrical insulation for electrical magnets, and biocompatibility for medical applications. By safeguarding magnets and enhancing their performance, coatings play a vital role in various industries, contributing to improved efficiency and reliability in diverse applications.
Under What Circumstances Do Magnets Need to Be Coated?
| Circumstance | Explanation |
| Corrosion protection | Magnets may need to be coated to protect them from corrosion, especially if they are used in environments with high humidity or exposure to corrosive substances. The coating acts as a barrier between the magnet and the corrosive elements, preserving its performance and lifespan. |
| Environmental protection | In certain applications, magnets may be exposed to harsh environmental conditions, such as extreme temperatures, moisture, or chemicals. Coating the magnets can help shield them from these adverse elements, preventing damage and ensuring reliable operation. |
| Mechanical protection | Some magnets are used in applications where they can encounter physical wear and tear, such as friction or impact. Coatings act as a protective layer, reducing the risk of damage and maintaining the magnet's structural integrity and magnetic properties. |
| Electrical insulation | Coatings can provide electrical insulation for magnets used in electronic or electrical applications. This prevents unwanted electrical conductivity between magnets and surrounding components, reducing the risk of short circuits and ensuring proper functioning. |
| Contamination prevention | In certain industries like medical and food processing, magnets are used to handle sensitive materials. Coating prevents the magnet's surface from shedding particles or contaminants, maintaining a clean environment and preventing contamination of the handled materials. |
| Improved handling and adhesion in assemblies | Coatings can enhance the magnet's surface properties, making them easier to handle during assembly processes. They can also improve adhesion to other materials, ensuring secure integration into the final product or system. |
| Aesthetic considerations | In consumer electronics or decorative applications, magnets might be coated to achieve a specific appearance or to match the product's overall design aesthetics, enhancing the visual appeal and making them more appealing to consumers. |
| Minimize friction and abrasion in moving parts | When magnets are employed in dynamic applications involving moving parts, a coating can minimize friction and abrasion, reducing wear and maintaining the magnet's efficiency and performance over an extended period. |
| Bio-compatibility in medical applications | In medical devices or implants that use magnets, coatings may be required to ensure bio-compatibility with the human body. Coatings prevent adverse reactions, tissue irritation, or potential toxic effects, making the medical device safer and more biologically compatible. |
| Noise reduction in certain applications | In specific applications where magnets create noise due to vibration or contact with other components, coatings can dampen the noise, leading to quieter operations and improved user experience. |
What Types of Magnet Coatings are There?
The different coatings and their properties are listed below to help you choose among the many options
Nickel
Nickel is the most common coating on magnets. It typically comes in 3 layers, which are nickel-copper-nickel. It protects rare-earth magnets from chipping and corrosion in ambient air. However, it does not serve as a protective coating from humidity, water, or salt water. Nickel coating is also a decorative finish and has a shiny metallic gray finish. It has a thickness of 15-25 um and works at approximately 200°C.
The main areas of application of nickel magnet coating are motors, medical devices, generators, pumps, sensors, automotive, etc., and several other industries.
Gold
Gold is used as an FDA-approved medical coating for in-body use, it is used as an undercoating of Ni-Cu-Ni. Like nickel coating, it helps to protect the magnet from corrosion in ambient air but also offers mild protection from humidity, water, or salt water. The thickness of the gold is very thin (approximately 0.1- 1um), so its performance in salt spray tests may be poor, as most gold coating is intended to be thin. Its max working temperature is approximately 200°C.
Zinc
Zinc coating offers good adhesion when glued with epoxy onto the steel. It is used for the protection of the magnet from corrosion in surrounding air and it offers mild protection from humidity, water, or salt water. However, it is not a fitting choice if the magnet is in a moisture environment. It has a thin thickness of 4-10 um and a maximum working temperature of approximately 120°C. Zinc coating is mostly used in low-temperature applications and where a little protective barrier is needed.
Epoxy
Unlike gold, zinc, and nickel, epoxy magnet coating works as an excellent barrier to salt, ambient air, and water or humidity. But it is slightly costlier than the first three alternatives. Although it can scratch easily and has a maximum working temperature of 15-30 um, it has very good adhesion to steel with magnet-rated glue. Epoxy coating is mainly used in the marine, motor, sensors, automotive, and consumer products industries.
Injection Molding / Plastic
This coating requires molds and tooling. It is an excellent protective covering for rare-earth magnets against breakage, impact, and corrosion. It can be used for coating medium-large magnets. Note that small magnets cannot be coated in plastic. They serve as a good protective coating against salt water, humidity, or water.
The color of the plastic can be tinted to almost any color. The common thickness of the coating is between 1 and 2 mm. The maximum working temperature will typically be determined by the type of ABS plastic selected. It is used for medical, educational, consumer products, etc.
Teflon (Molded PTFE)
Teflon coating also requires molds and tooling, and that can determine its cost. However, it is an excellent protection for a magnet against breakage, impact, and corrosion. The molding is available for magnets that are medium to larger but does not work for small magnets. It is good for protecting rare-earth magnets from humidity, fluids, and autoClave. The common thickness is between 1.5 and 3 mm with a maximum working temperature of approximately 2500°C. Teflon coating is predominantly used in the medical and food industries.
Which Coating is Best for Your Magnet?
The best coating for your magnet depends on your specific application requirements. If you need general corrosion resistance for indoor use, a nickel (Ni-Cu-Ni) coating is a popular and cost-effective choice. For applications where biocompatibility is crucial, a gold (Au) or epoxy coating may be more suitable. If you require protection against moisture and chemicals, epoxy coatings are an excellent option.
Consider factors like environmental conditions, budget, and the magnet's intended use to determine the most appropriate coating for optimal performance and longevity. Consulting with coating specialists or magnet manufacturers can help you make an informed decision tailored to your magnet's needs.
Conclusion
Thank you for reading our article, we hope it helps you gain a better understanding of magnet coatings. We provide our customers with advice and solutions for optimum application of magnets. We put our rich experience in magnetic field at your disposal. Please contact us and we will be happy to answer your questions.
As the world's leading magnet manufacturer, XHMAG has been engaged in the R&D, manufacture and sales of magnets. We provide our customers with high quality permanent magnets such as Samarium Cobalt Magnets, Neodymium Magnets, AlNiCo Magnets, Ferrite Magnets (Ceramic Magnets) at very competitive prices. If you have needs, please contact us, or visit our website!
