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What is the Best protective coating for magnets (5"x3"x0.5") used in Oil/Gas pipes.

What is the Best protective coating for magnets (5"x3"x0.5") used in Oil/Gas pipes.

What is the Best protective coating for magnets (5"x3"x0.5") used in Oil/Gas pipes.

(OP)
Hello Everyone,
I am glad to be on this amazing forum of Engineers. So I am working on this project where I have to select the best coating (to resist corrosion and increase strength) for magnets which will be used in oil/gas pipes and will be in contact with fluids (H2S, Mercury). The type of magnet I am using is NdFeB grade N40SH. I searched online and found different types like PVD, passivated coating, phenolic coating. I am not sure which one is the best for my application. I want something that is reliable, durable, has strong chemical resistance, abrasion resistance, etc . Please let me know if you know any coating for magnets that can fit into my application. Thanks a lot in Advance.

Thanks
Masih

RE: What is the Best protective coating for magnets (5"x3"x0.5") used in Oil/Gas pipes.

No NdFeB coating will survive that environment. The only practical option is to completely seal the magnet in an enclosure made of corrosion resistant metal. Inconel is a popular choice.

RE: What is the Best protective coating for magnets (5"x3"x0.5") used in Oil/Gas pipes.

(OP)
Magmike Thanks for your reply.

What if you had no option other than coating? Can you suggest any coating that will last the most?

RE: What is the Best protective coating for magnets (5"x3"x0.5") used in Oil/Gas pipes.

If I was told the magnets were going to be in that environment and the only option was a coating, then I would not take the order. It is doomed for failure.

RE: What is the Best protective coating for magnets (5"x3"x0.5") used in Oil/Gas pipes.

What is the purpose of your magnet?

RE: What is the Best protective coating for magnets (5"x3"x0.5") used in Oil/Gas pipes.

(OP)
Magmike: Thanks for your reply again. I still think there are some good coatings out there.
Cmpositepro: The magnets are used to collect the iron/metal particles from the fluids.

RE: What is the Best protective coating for magnets (5"x3"x0.5") used in Oil/Gas pipes.

Noe has the worst corrosion resistant among all magnets due to Nd-rich phase. coating can help using in humid situation, in severe condition, coating is not sufficient. if you donot have option, try everlube coating, normal Nickel, Tin cna only resist in humidity.

collecting particles seem not to be a critical application, recommend to use Sm-Co or AlNiCo magnets to against the corrosion. you can increase dimension or optimize the design to increase the "sucking" force. Note that no coating can increase magnetic strength.

RE: What is the Best protective coating for magnets (5"x3"x0.5") used in Oil/Gas pipes.

(OP)
MagBen: I really appreciate your response.
What about passivation or PVD coating? Any idea if that's better than everlube ??

RE: What is the Best protective coating for magnets (5"x3"x0.5") used in Oil/Gas pipes.

passivation may be not even as good as Ni-electroplating. PVD will depend on what agents to apply, and what tehcniques to use. Evaporating normally yield defected coating (e.g. voids, pores), sputtering could give you a denser layer. Al PVD using Al as a sacrificial anode cannot fully pretect NdFeB. AlN, TiN ceramic PVD sounds a better solution, but as long as the layer is broken, nothing can prevent corrosion.

Housing your magnet with 4xx stainless steel (not sure if anyone did this or not) not only help resist but increase the mechanical strenght. make sure fully sealing wihtout leakage.

RE: What is the Best protective coating for magnets (5"x3"x0.5") used in Oil/Gas pipes.

If designed wisely, the stainless steel can strengthen your magnetic performance.

i cannot tell the difference of corrosion reistance between everlube and PVD.

RE: What is the Best protective coating for magnets (5"x3"x0.5") used in Oil/Gas pipes.

Ben in on the mark. If I had to do it for a short while I would first see if I could move to a design using Alnico magnets. And then I would cold spray them with Al or Zn.
If I had to use Neo I would use electroless Ni with a conformal coating over it.
Another option over the Ni would be a resin like PEEK or PPS. Due to permeation and reactivity of hte Neo you will have finite life (measured in months not years).

I have seen hermetic metal cans with 316 SS sides (non-magnetic) and 448 end plates (ferromagnetic) on the pole faces. These are laser welded, and if they are made right don't change the external field at all.

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

RE: What is the Best protective coating for magnets (5"x3"x0.5") used in Oil/Gas pipes.

Ed, good to know there are such kinds of design in real life. and yes, one cannot use a hemetic metal can with only 4xx magnetic SS in which situation the magnetic flux will circle around, the can will only have a shield function.

RE: What is the Best protective coating for magnets (5"x3"x0.5") used in Oil/Gas pipes.

Ben, I looked back at some pictures and remembered what they really did.
They made rectangular cans by deep drawing 305 SS (can't use 304 or 316 unless you want to re-anneal, they will become magnetic when worked). The cans were a tight fit for the magnets, and they had a flange around the top edge.
The magnets were coated with a resin, but just enough so that they wouldn't rattle.
They were put into the cans, vacuumed and Ar backfilled, and a 448 cover plate was welded on.

So only one pole had a magnetic face, but the bottom of the can was only 0.012" thick so it didn't add much air gap.

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

RE: What is the Best protective coating for magnets (5"x3"x0.5") used in Oil/Gas pipes.

(OP)
Magben and Edstainless:
Let me first tell you that you guys have helped me alot and you are amazing people.
I am still working on this issue and recently found out about black epoxy coating for magnets? Would you guys suggest it? The magnets will not be exposed to process fluids continuously. The magnets will be exposed to oil/gas for one day every 6 months. So coating should be good enough but I just want to make sure that I have the best coating when it comes to the life of the coating.

Thanks
Masih

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