Surface treatment on steel for NiCuNi magnet bonding

[Cheetos]

I'm looking into bonding NiCuNi magnet to steel plate using acrylic adhesive. I have 2 questions about surface preparation:
1) In the past, when I get steel plate from overseas, they usually have primer. Should I request bare metal with oil coating? My preference is coating of some kind. Prefer not to get a industrial washer to clean off the oil coating.
2) Should surface roughness be around 32(0.8)~ 63(1.6)?

 

[EdStainless]

You are going to have to strip whatever is on the surface.
So decide which you will have an easier time removing, oil or primer.
The roughness relates to your adhesive and the flatness of the parts.
Talk with your adhesive supplier about min/max roughness and min/max bond thickness.

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P.E. Metallurgy, consulting work welcomed

 

[MagMike]

I concur with Ed.

I would only add that most acrylic adhesives work best with smooth surfaces. You don't need a mirror surface finish on the steel but something reasonable that isn't going to drive the cost up.

 

[Cheetos]

@MagMike, I heard adhesives typically work the best when you rough up the surface to increase the contact surface area. Do you think this is still applicable for acrylic adhesives?

 

[EdStainless]

It depends on the specific adhesive.

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P.E. Metallurgy, consulting work welcomed

 

[MagMike]

Ed is correct.

Epoxies generally work well with roughened surfaces. In my experience, acrylics work well with smooth surfaces. There are exceptions to both.

 

[hacksaw]

Most acrylic cements are only good at room temperature and best suited to smooth synthetic (not metallic) surfaces.
In some industries acrylic cements are prohibited, due to poor reliability at storage or shipping temperatures.

If this is a hobby project it may be fine, but otherwise you need to test the bond durability.

 

[hacksaw]

By the way:

"Galvanic Nickel Plating (NiCuNi) The galvanic nickel plating is a widespread method to coat sintered neodymium magnets. "