Introduction to Magnet Coatings
This article is written by New Favor Industry Co., Ltd.
New Favor specializes in the manufacturing and application solutions of high-performance rare earth magnets such as Neodymium Iron Boron (NdFeB), dedicated to providing stable and reliable magnetic component support to clients worldwide.
Whether you are in the electronics, energy, or automation industries, our expertise ensures efficient and precise magnetic solutions tailored to your needs.
In industrial applications,whether motors, sensors, or wind power systems—the durability and stability of magnets are critical. To enhance corrosion resistance in environments such as humidity and salt spray, surface coatings are commonly applied. Below are common types of magnet coatings, their use cases, and performance comparisons to help you choose the best coating solution.
Why Do Magnets Need Coatings?
NdFeB magnets are particularly prone to oxidation and rust when exposed to air, which leads to loss of magnetic strength and even structural failure. Coating helps：
- Prevent oxidation and moisture damage
- Improve mechanical strength
- Extend product lifespan
- Comply with RoHS and environmental standards
Common Magnet Coating Comparison
1. Nickel-based Coating： The most common surface treatment for sintered NdFeB magnets
Nickel coatings provide excellent corrosion resistance and strong adhesion, suitable for most industrial uses.
| Coating Type | Coating Composition | Color | Thickness(µm) | SST (hr)) | PCT(Hours) |
|---|---|---|---|---|---|
| Nickel | Ni+Ni | Silver-white | 10-20 | >24-72 | >24-72 |
| Nickel-Copper-Nickel | Ni+Cu+Ni | Silver-white | 10-20 | >24-72 | >24-72 |
| Black Nickel | Ni+Cu+Ni | Glossy black | 10-20 | >48-96 | >48 |
| Tin (Sn) | Ni+Cu+Ni+Sn | Silver | 10-25 | >36-72 | >48 |
2. Epoxy Coating: An excellent choice for corrosion protection
Especially suitable for humid or chemically exposed environments, commonly used on compression bonded neodymium magnet.
| Coating Type | Coating Composition | Color | Thickness(µm) | SST(Hours) | PCT(Hours) |
|---|---|---|---|---|---|
| Epoxy | Epoxy | Black/Gray | 10-30 | >48 | - |
| Nickel-Copper-Epoxy | Ni+Cu+Epoxy | Black/Gray | 15-30 | >72-108 | - |
| Zinc-Epoxy | Zn+Epoxy | Black/Gray | 15-25 | >72-108 | - |
3. Zinc (Zn) Coating：An eco-friendly certified choice
Zinc coatings with trivalent chromium passivation comply with RoHS standards and are widely used in automotive and electronics industries.
| Coating Type | Coating Composition | Color | Thickness(µm) | SST(Hours) | PCT(Hours) |
|---|---|---|---|---|---|
| Blue-White Zinc | Zn | Blue-white | 5-8 | >16-48 | - |
| Rainbow Zinc / Multicolor Zinc | Zn | Multicolor / Rainbow | 5-8 | >36-72 | - |
4. Other Metallic Coatings：Designed for specialized electronic and medical applications
Gold (Au) and silver (Ag) coatings offer high conductivity and strong oxidation resistance, ideal for precision electronic components despite higher cost.
| Coating Type | Coating Composition | Color | Thickness(µm) | SST(Hours) | PCT(Hours) |
|---|---|---|---|---|---|
| Gold (Au) | Ni+Cu+Ni+Au | Gold | 10–15 | >12 | >48 |
| Silver (Ag) | Ni+Cu+Ni+Ag | Silver | 10–15 | >12 | >48 |
5. Uncoated Surface Treatment: For temporary use only
Processes like phosphating or passivation offer short-term rust protection and are not recommended for long-term use.
| Coating Type | Coating Composition | Color | Thickness(µm) | SST(Hours) | PCT(Hours) |
|---|---|---|---|---|---|
| Passivation | - | Black and Gray | 1–3 | - | - |
| Phosphated | - | Black and Gray | 1–3 | - | - |
*Note: Data in the above tables may vary slightly by specification. For exact values, please contact New Favor Industry Co., Ltd.
FAQ
Q： Why is Ni-Cu-Ni coating most commonly used for sintered NdFeB magnets？
It offers excellent corrosion resistance and structural stability, ideal for outdoor or humid environments.
Q：Can epoxy coatings be used in high-temperature environments？
Epoxy performs well at room temperature but may degrade above 150°C. Metal coatings are recommended instead.
Q：Are there any magnet coatings compliant with RoHS？
Yes, Zn coatings with trivalent chromium passivation comply with RoHS and are suitable for EU markets.
New Favor Industry Co., Ltd. offers a wide range of magnet coating solutions tailored for industrial, electronic, medical, and corrosion-resistant applications. Contact us for personalized recommendations.
