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Passivated NdFeB

Passivated NdFeB

Passivated NdFeB

Can somenoe tell me something about this process?  Does it provide corrosion resistance?

From http://ningbo-unimag.com/Article-products.asp?id=83&seq=18


Our most advanced technology: we can make two different series of sintered NdFeB magnets--- ordinary book mold alloy and magnets (HAST NdFeB) based on a strip cast alloy which gives a better chemical stability. We has invested in the production technology enabling to use strip cast material. HAST NdFeB magnets have higher anticorrosion and can last for 7 days under 131 degree Celsius, 100% humidity and 3atm with loss of weight less than 5mg/cm2.

From http://www.alibaba.com/product-gs/266632909/passivated_ndfeb_magnet.html


We produce ndfeb magnet without coating, many motor customers need passivated ndfeb magnet


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RE: Passivated NdFeB

I've done salt fog testing on passivated sintered NdFeB parts and they didn't last 24 hours.  They might be OK in a gentler environment, but I haven't tested for that.

Admittedly, I did the testing 9 years ago and there have been improvements in chemistry & processing since then.

RE: Passivated NdFeB

If you add a selective amount of impurities you can make the material resist initiation of corrosion.
Once corrosion starts I don't think that it will be any different.

= = = = = = = = = = = = = = = = = = = =
Plymouth Tube

RE: Passivated NdFeB

There is no viable method for passivating NdFeB for any useful amount of corrosion resistance. The reactive phase of NdFeB is the Nd-rich grain boundary region. Any process that starts the oxidation of this phase will invariable produce structural breakdown of the material.

In use, we ALWAYS coat the NdFeB magnets with some sort of protective material to encapsulate or shield the magnet from the environment. I would view the article you read as an error in translation.

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