HOW TO PROTECT MAGNETS IN HUMID ENVIRONMENTS？

Introduction

Magnets are essential components in a wide range of industries, from electronics to aerospace. However, their exposure to moisture, particularly in humid environments, can significantly reduce their effectiveness and lifespan. Neodymium magnets (NdFeB) and Samarium Cobalt magnets (SmCo) are two common types susceptible to moisture and corrosion.

This article will explore the causes, solutions, and case studies highlighting successful protection techniques. Hope that you can learn something about the protection and maintenance of different magnets.

Causes of Magnet Corrosion Due to Moisture

1. Moisture’s Effect on Neodymium (NdFeB) Magnets:

Neodymium magnets, also known as NdFeB magnets, are widely used because of their strong magnetic fields. However, they have a major vulnerability—corrosion, especially in humid or wet environments. The primary cause is that neodymium is highly reactive to moisture. When exposed, moisture seeps into the micro-cracks or gaps in the protective coating, leading to oxidation of the neodymium core. Over time, this weakens the structure of the magnet, causing it to corrode and lose its magnetic strength.

2. Samarium Cobalt (SmCo) Magnets and Moisture:

SmCo magnets are known for their stability at high temperatures and their resistance to corrosion compared to NdFeB magnets. However, while more resistant, SmCo magnets are not entirely immune to moisture. Prolonged exposure to humidity can still lead to corrosion, especially if protective coatings are compromised or environmental conditions are particularly harsh, such as in marine or offshore applications.

3. Humid Environment Challenges:

Humidity plays a significant role in accelerating the corrosion process of magnets. The presence of moisture in the air, especially combined with salt or other corrosive elements, creates an electrochemical reaction on the surface of the magnet. Over time, this reaction leads to pitting, rust, and loss of magnetism. For industries relying on magnets in outdoor settings or moisture-prone environments, this degradation can result in failure of critical systems.

Solutions to Protect Magnets against Moisture

1. Coatings for Neodymium (NdFeB) Magnets:

To protect NdFeB magnets from moisture, manufacturers use various types of protective coatings. The most common are nickel-copper-nickel (Ni-Cu-Ni) coatings, which form a durable, corrosion-resistant layer around the magnet. For environments where corrosion risks are higher, more advanced coatings like PTFE (polytetrafluoroethylene) or epoxy can be applied. These coatings provide additional barriers to moisture penetration, enhancing the magnet's resistance to humidity and prolonging its lifespan.

Related reading: Types of Neodymium Magnet Coatings: Protecting the World's Strongest Magnets

2. Protection Methods for Samarium Cobalt (SmCo) Magnets:

Although SmCo magnets have better inherent corrosion resistance than NdFeB magnets, applying a protective coating can further increase their durability in moist environments. A thin layer of nickel or gold plating is often used to protect the magnet’s surface from oxidation. In extreme environments, additional layers of corrosion-resistant materials may be applied to enhance protection. Furthermore, placing SmCo magnets in sealed housings or enclosures prevents direct exposure to moisture, reducing the risk of corrosion.

3. Other Protective Methods:

To protect magnets from moisture, there are several other effective strategies:

• Encapsulation: Encapsulating the magnet in a protective material such as plastic, resin, or stainless steel provides a barrier against moisture. This process seals the magnet completely, preventing direct exposure to environmental moisture. Encapsulation is particularly useful for applications where magnets are submerged or frequently exposed to water, as it offers long-term protection without affecting the magnet's performance.
• Sealed Housings: In some applications, magnets can be housed inside hermetically sealed containers or enclosures. These airtight housings can be made of corrosion-resistant metals, ceramics, or even certain polymers, effectively isolating the magnet from the surrounding environment. This method is especially valuable in high-moisture or corrosive settings, such as marine environments or chemical processing plants.
• Environmental Control: Another approach to protecting magnets is by managing the environment in which they operate. In indoor or controlled industrial environments, installing dehumidifiers or moisture barriers can reduce the overall humidity, minimizing the risk of corrosion. Additionally, using magnetic assemblies in temperature- and moisture-regulated areas can prolong their lifespan.
• Use of Desiccants: Desiccants are moisture-absorbing materials, like silica gel or activated charcoal, that can be used in storage or packaging to keep the humidity levels low. By placing desiccants near magnets during storage or inside sealed assemblies, you can prevent moisture buildup that could otherwise lead to corrosion.
• Magnetic Shielding: Creating a protective layer by adding magnetic shielding around the magnet can also help. While this method is more common for controlling magnetic fields, it can also offer a layer of protection from environmental elements if the shielding materials are corrosion-resistant.

Case Studies: Successful Moisture Protection

1. Offshore Wind Turbines and Neodymium Magnets:

In offshore wind turbines, neodymium magnets are a core component of the electric generators. These turbines operate in a highly humid, corrosive environment due to the constant presence of saltwater and sea spray. To combat corrosion, advanced protective coatings such as epoxy and nickel-plating have been applied to the NdFeB magnets used in these turbines. Moreover, the turbines’ generators are housed in waterproof, sealed units to further limit exposure to moisture. This combination of coatings and enclosures has significantly extended the operational lifespan of the magnets, reducing maintenance costs and enhancing performance.

2. Samarium Cobalt Magnets in Aerospace Applications:

In aerospace applications, SmCo magnets are frequently used due to their stability at high temperatures. However, in moisture-prone environments such as fuel systems or exterior components, the magnets need additional protection. In one case, a manufacturer applied a thin layer of nickel coating to SmCo magnets used in the construction of aircraft sensors. The nickel coating provided a barrier against corrosion, even when the magnets were exposed to changing humidity levels during flight. This protection ensured the reliability of the sensors over long periods, even in harsh conditions.

Conclusion

Without proper protection, exposure to humid environments can lead to corrosion, degradation, and loss of magnetic properties. Solutions such as protective coatings, sealed housings, and environmental control play a critical role in safeguarding magnets from moisture damage. From offshore wind turbines to medical devices, industries that rely on magnets in humid conditions can benefit greatly from these protective measures, ensuring longevity and reliable performance across various applications. For more information, please check Stanford Magnets.