Surface Treatment of Magnets
The surface treatment of neodymium magnets plays a crucial role in their performance and longevity. Neodymium magnets, also known as NdFeB magnets, are extremely powerful permanent magnets made from an alloy of iron, boron, and neodymium. Surface treatment refers to the process of applying a protective layer or coating to the outer surface of the neodymium magnet. This treatment is necessary to prevent the magnet from corroding and to improve its overall durability. The most common types of surface treatments for neodymium magnets include NiCuNi plating, Zinc plating, and Epoxy coating.
One of the main reasons why surface treatment is important for neodymium magnets is their susceptibility to corrosion. Neodymium magnets are primarily composed of iron, which is prone to rusting when exposed to moisture and oxygen. By applying a protective coating, corrosion can be significantly reduced, extending the lifespan of the magnet.
Another reason for surface treatment is to enhance the magnet's performance. The coating can provide a smoother surface, reducing friction and allowing for better magnetic properties. Certain surface treatments, such as nickel plating or gold plating, can improve the magnet's resistance to high temperatures, making it suitable for applications that involve heat. Surface treatments also enable neodymium magnets to be compatible with various environments and applications. For example, epoxy coatings can provide insulation, allowing the magnet to be used in electrical applications without short-circuiting. Coatings can also protect the magnet from chemicals or abrasion, making it suitable for use in corrosive environments or in applications where friction and wear are present.
Surface treatments are necessary for neodymium magnets to protect against corrosion, enhance performance, increase durability, and ensure compatibility with specific environments and applications. By applying the appropriate surface treatment, the lifespan and effectiveness of neodymium magnets can be significantly improved.
Below is a list of plating/coating and their feathers for your reference.
| Surface Treatment | ||||||
| Coating | Coating Thickness (μm) |
Color | Working Temperature (℃) |
PCT (h) | SST (h) | Features |
| Blue-White Zinc | 5-20 | Blue-White | ≤160 | - | ≥48 | Anodic coating |
| Color Zinc | 5-20 | Rainbow color | ≤160 | - | ≥72 | Anodic coating |
| Ni | 10-20 | Silver | ≤390 | ≥96 | ≥12 | High temperature resistance |
| Ni+Cu+Ni | 10-30 | Silver | ≤390 | ≥96 | ≥48 | High temperature resistance |
| Vacuum aluminizing |
5-25 | Silver | ≤390 | ≥96 | ≥96 | Good combination, high temperature resistance |
| Electrophoretic epoxy |
15-25 | Black | ≤200 | - | ≥360 | Insulation, good consistency of thickness |
| Ni+Cu+Epoxy | 20-40 | Black | ≤200 | ≥480 | ≥720 | Insulation, good consistency of thickness |
| Aluminium+Epoxy | 20-40 | Black | ≤200 | ≥480 | ≥504 | Insulation, strong resistance to salt spray |
| Epoxy spray | 10-30 | Black, Grey | ≤200 | ≥192 | ≥504 | Insulation, high temperature resistance |
| Phosphating | - | - | ≤250 | - | ≥0.5 | Low cost |
| Passivation | - | - | ≤250 | - | ≥0.5 | Low cost, invironment friendly |
| Contact our experts for other coatings! | ||||||
Types of coatings for magnets
NiCuNi: The nickel coating is composed of three layers, nickel-copper-nickel. This type of coating is the most widely used and provides protection against corrosion of the magnet in outdoor situations. Processing costs are low. The maximum working temperature is approximately 220-240ºC (depending on the maximum working temperature of the magnet). This type of coating is used in engines, generators, medical devices, sensors, automotive applications, retention, thin film deposition processes, and pumps.
Black Nickel: The properties of this coating are similar to those of the nickel coating, with the difference that an additional process is generated, the black nickel assembly. Properties are similar to those of conventional nickel plating; with the particularity that this coating is used in applications that require that the visual aspect of the piece is not bright.
Gold: This type of coating is often used in the medical field and is also suitable for use in contact with the human body. There is an approval from the FDA (Food and Drug Administration). Under the gold coating, there is a sub-layer of Ni-Cu-Ni. The maximum working temperature is also about 200 ° C. In addition to the field of medicine, gold plating is also used for jewelry and decorative purposes.
Zinc: If the maximum working temperature is less than 120 ° C, this type of coating is adequate. The costs are lower and the magnet is protected against corrosion in the open air. It can be glued to steel, although a specially developed adhesive must be used. The zinc coating is suitable provided that the protective barriers for the magnet are low and low working temperatures prevail.
Parylene: This coating is also approved by the FDA. Therefore, they are used for medical applications in the human body. The maximum working temperature is approximately 150 ° C. The molecular structure consists of ring-shaped hydrocarbon compounds consisting of H, Cl, and F. Depending on the molecular structure, different types are distinguished as Parylene N, Parylene C, Parylene D, and Parylene HT.
Epoxy: A coating that provides an excellent barrier against salt and water. There is a very good adhesion to steel, if the magnet is glued with a special adhesive suitable for magnets. The maximum working temperature is approximately 150 ° C. The epoxy coatings are usually black, but they can also be white. Applications can be found in the maritime sector, engines, sensors, consumer goods, and the automotive sector.
Magnets injected in plastic: are also called over-molded. Its main characteristic is its excellent protection of the magnet against breakage, impacts, and corrosion. The protective layer provides protection against water and salt. The maximum working temperature depends on the plastic used (acrylonitrile-butadiene-styrene).
Formed PTFE (Teflon): Like the injected / plastic coating also provides excellent protection of the magnet against breakage, impacts, and corrosion. The magnet is protected against moisture, water, and salt. The maximum working temperature is around 250 ° C. This coating is mainly used in the medical industries and in the food industry.
Rubber: The rubber coating protects perfectly from breakage and impacts and minimizes corrosion. The rubber material produces very good slip resistance on steel surfaces. The maximum working temperature is around 80-100 ° C. Pot magnets with rubber coating are the most obvious and widely used products.
We provide our clients with professional advice and solutions on how to protect their magnets and obtain the best application of the magnet. Contact us and we will be happy to answer your question.