Welcome to the ultimate guide on zinc plating for neodymium magnets.
We’ll walk you through everything you need to know about galvanizing zinc on strong magnets.
After reading this post, you will understand whether this surface treatment is right for you.
Let’s get started.
Overview
Rust poses a threat to neodymium magnets, but zinc plating thwarts corrosion.
Zinc electroplating deposits a protective zinc coating on neodymium magnet surfaces vulnerable to oxidation.
Though prized for their unmatched magnetic properties, neodymium magnets corrode when exposed to moisture and oxygen.
The zinc layer acts as a barrier, intercepting rust before it can degrade the magnet’s power.
Zinc resists corrosion far better than neodymium alone.
Thanks to zinc’s noble resistance, the treated magnet avoids the pitted decay of rust.
Zinc plating has shielded neodymium magnets from rust damage for decades, maximizing their magnetic lifespan.
Zinc is a silvery-white, slightly bluish metal, with features like:
- Relatively brittle and is only ductile when heated to 100 – 150°C.
- Relatively low hardness and poor abrasion resistance.
- Soluble in both acids and bases, especially, when it contains impurities with a positive potential.
The zinc coating applied through electroplating is pure and has an even structure.
- Stable and does not react easily with other chemicals at normal room temperatures.
The zinc coating forms a shiny, white protective film that is very stable when exposed to regular air, gasoline, or humid air with carbon dioxide.
However, the zinc coating is less resistant to wear and corrosion when used in ocean environments and seawater.
Especially in high temperature, high humidity and atmosphere containing organic acids, the corrosion resistance of the galvanized layer is extremely poor.
Advantages
Electro-galvanizing process is more mature, simple operation and less investment.
- It has the lowest cost in the protective coating of NdFeB magnets.
- The production volume of zinc plating as a protective coating is the largest, accounting for about 50% of the total production volume of electroplating.
Zinc plating has many advantages, such as:
- Zinc is abundant in nature and relatively cheap compared to other metals.
- Zinc plating is easy to apply and does not require expensive equipment or skills.
Zinc plating creates a barrier that prevents moisture and oxygen from reaching the metal surface, which can cause rusting.
Zinc also acts as a sacrificial anode, meaning it will corrode before the metal does, providing an extra layer of protection.
Zinc plating can withstand high temperatures, abrasion, and chemical exposure without losing its effectiveness.
Zinc plating can also increase the hardness and strength of the metal surface, making it more resistant to damage.
These are some of the advantages of zinc plating that make it a popular choice for neodymium magnets.
Disadvantages
Zinc plating also has some drawbacks that you should be aware of.
Some of the drawbacks of zinc coatings are:
Zinc coatings can be damaged by abrasion, impact, or bending, which can expose the underlying metal to corrosion.
Zinc coatings can also be affected by hydrogen embrittlement, which is a condition where hydrogen atoms enter the metal and cause it to crack or fracture.
This can happen during the plating process or during service, especially in high-stress or high-temperature environments.
To prevent or reduce hydrogen embrittlement, zinc-plated parts should be baked after plating to diffuse the hydrogen out of the metal.
Zinc coatings can have different levels of corrosion resistance depending on the type and thickness of coating.
- Some zinc coatings may not provide enough protection in harsh or aggressive environments, such as marine, industrial, or acidic atmospheres.
- For example, zinc plating and mechanical plating are thinner and cheaper than other zinc coatings, but they are also less effective and more prone to wear and contamination than other zinc coatings.
Common quality issues
Some frequently occurring plating problems that can occur if zinc is not properly applied.
You need to check when ordering custom neodymium magnets.
Pitting
This is when small holes or pits form on the surface of the zinc coating, creating a rough or uneven appearance.
Pitting can affect the corrosion resistance, wear resistance, and aesthetic quality of the zinc coating.
Pitting can be caused by gas bubbles, impurities, or contaminants in the plating solution or on the substrate.
How to identify:
Flaking or peeling
This is when the zinc coating detaches from the substrate, exposing the bare metal or material underneath.
Flaking or peeling can affect the performance, durability, and appearance of the coated product.
Flaking or peeling can be caused by poor adhesion, thermal stress, mechanical damage, or contamination of the coating surface.
How to identify:
Pinholes
These are small holes or gaps in the zinc coating that expose the substrate to the environment.
Pinholes can increase the risk of corrosion, oxidation, or contamination of the coated product.
Pinholes can be caused by dust, dirt, or foreign particles on the coating surface, or by insufficient coating thickness or coverage.
How to identify:
Comparing Zinc and Nickel plating
Price
Zinc plating is cheaper than nickel plating, as it has lower material and production costs. Zinc plating also has a longer shelf life than nickel plating, which means it does not need to be replaced as often. Therefore, zinc plating may be more cost-effective and efficient than nickel plating in the long run.
Appearance
Nickel plating has a brighter and shinier appearance than zinc plating, as it has better polishing properties. Nickel plating also comes in various colors and finishes, such as clear/white, yellow, black, olive drab, satin, pearl, etc. Zinc plating has a duller and rougher appearance than nickel plating, as it has lower polishing properties. Zinc plating also has fewer color and finish options than nickel plating.
Performance
Nickel plating has higher hardness, magnetic qualities, lubricity, and compatibility with subsequent finishes such as chromium coatings than zinc plating. Nickel plating also improves the temperature resistance of the magnet and reduces the loss of magnetic flux caused by short circuits. Zinc plating has higher ductility, customization options, improved precision and aesthetics of the coating, environmental friendliness, and recyclability than nickel plating. Zinc plating also forms a sacrificial layer that corrodes before the base metal does, a process known as galvanic action, which enhances the corrosion resistance of the magnet.
Thickness
Nickel plating is thicker than zinc plating, which means it provides more protection and coverage for the magnet. However, it also means that it adds more weight and size to the magnet, which may affect its performance and application. Zinc plating is thinner than nickel plating, which means it is lighter and more compact for the magnet. However, it also means that it may have more defects or gaps in the coating, which may expose the magnet to corrosion or oxidation.
Conclusion
Now you don’t need to spend hours searching for zinc plating on neodymium magnets anymore.
If you need custom neodymium magnets, don’t hesitate to reach out.
Our engineering team can help select the optimal coating for you.
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