Sm2Co17 in water 1

[leslie2000]

We have several questions about Sm2Co17 material.

1 How is its anti-corrosion capacity in water condition. how long will the magnet be corroded?
2 Is it necessary to coat the magnet? If yes, what is the best coating?
3 How about SmCo5, comparing with Sm2Co17.Because SmCo5 dont contain Fe, will it be better?

We are using this magnet in magnetron sputter, so the magnet is exposed to water continuously.

Thanks for any information.

 

[sreid]

I'd suggest a Parylene coating to avoid any corrosion issues.

http://en.wikipedia.org/wiki/Parylene

 

[leslie2000]

Sreid: considering the possible high working temperature of Sm2Co17, do you think Parylene can stand for 300-350centigrade? Do you have any technical data available?

 

[sreid]

Parylene N has a melting temperature of 410 C.

http://www.parylene.com/technology/specifications-properties.html

 

[sreid]

SmCo can probably be Nickel plated ( just like Neo can). Nickel plating would probably eliminate any concerns you have about corrosion and temperature. I'd contact a supplier such as MCE.

http://www.mceproducts.com/

 

[leslie2000]

Thank you Sreid for your information. I have another question: do you think it is possible to use SmCo magnet without coating in water (magnet is exposed to continuous water)?

 

[sreid]

Information on SmCo corrosion in hot water probably exists somewhere but I don't know where that is. One thing you could do is to do the experiment yourself.

I was suggeting coatings based on the theory that if corrosion is peceived to be a potential problem, mitigate the problem from the begining.

Remember that corrosion generally proceeds faster at higher temperatures and that water usually has disolved oxygen and minerals that can accelerate corrosion.

 

[EdStainless]

No you will not be able to use either 1:5 or 2:17 in a wet or humid environment without coating. You will find that 2:17 bis slightly more corrosion resistant than 1:5, but it is nothing to write home about.
Watch out, with any coating you will need to be able to test for bond, Hydrogen damage (with Ni), and holidays,

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

 

[leslie2000]

Thanks EdStainless, can you give me a suggestion on what coating will be better for such application? So we can find a direction to do some testing here.

 

[MagMike]

EdStainless: Are you certain about the 2:17 being better than 1:5 regarding corrosion resistance? I've found otherwise. I've always thought the 1:5 would behave better because it has none to minimal levels of iron.

Leslie2000: Ask your supplier(s) what coatings they offer for SmCo and start testing.

 

[EdStainless]

The problem isn't the Fe, it is the Sm. By nature these alloys contain multiple phases. The phases are enough different in composition that galvanic corrosion is assured.

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

 

[drmagnet]

The several commercially available permanent magnets can be ranked in order of their corrosion resistance (to moisture) as follows:
1) Ferrite, 2) Alnico, 3) FeCrCo, 4) SmCo, 5) NdFeB

Corrosion in water is due to: 1) galvanic couple between dissimular phases (as pointed out by EdStainless) and 2) oxidation of the metals. although dissolved oxygen is minimized above about 150 ºF, it should still be a concern.

The common coatings for metallic permanent magnets are: 1) epoxy (spray), 2) E-coat (dip epoxy), 3) Parylene, 4) Nickel plate (electrolytic), 5) Aluminum IVD, 6) Nickel plate (electroless), 7) Hybrid coatings such as conversion coating plus expoxy. There are numerous others in limited use.

For SmCo at elevated temperature, you should consider electrolytic nickel plating. If there are no acids or salts in the water, this should serve you well. Be aware that there are only a limited number of companies that understand how to plate rare earth magnets (SmCo and NdFeB).