Electropolishing of small stainless steel parts with intricate shape 3

[Elena Kot]

Hello!
Could you please give recommendations on holding methods of small parts with complex shape (brackets for orthodontic treatment) on the electrode? They should be attached to the anode in order to conduct electricity, but how to mount them properly?
The bracket design is attached.

Thank you,

Elena

 

[MikeHalloran]

To the limited extent to which I understand it, electropolishing requires an electrode of opposite polarity which has a shape complementary to the part to be polished, and a modest clearance space between the two, large enough for electrolyte to circulate.

I.e., to electropolish the inside of a cup shaped object, you would need an electrode that would basically almost fill the cup.

I think the shaped electrode is required in order to provide a roughly uniform current field over the surface to be polished.

In your case, a complementary electrode would have an incredibly complex geometry, and might have to disassemble like a puzzle in order to extract your workpiece, or maybe you could polish in several steps, which cuts into the already not so great speed.

Your part also seems specifically designed to capture tumbling media, so bulk mechanical polishing might not be attractive as an alternative.

How do you polish the part now?


Mike Halloran
Pembroke Pines, FL, USA

 

[EdStainless]

I wouldn't electropolish them, for the reasons mentioned above.
You could tumble them in a very fine abrasive with a sulfuric/phosphoric acid mixture similar to the one used for EP.
These are sold for doing 'bright work'. The combination of very fine abrasion and the acid will result in a highly polished finish.

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P.E. Metallurgy, Plymouth Tube

 

[Elena Kot]

Mike, Ed, thank you for your comments!
Actually, I have not polished them yet and need to find a way for the best possible option for finishing.

 

[Elena Kot]

EdStainless, could you please advise if a tumbling without acids makes it possible to achieve better surface finish?
Will the next mixture work: fine abrasive media + water + burnishing compound?

 

[EdStainless]

You have to make sure that you don't get any burnishing.
If you smear any metal on the surface you invite serious corrosion issues.
The use of acid will accelerate the process and help remove 'roughness' from the surface.
These acid mixtures are not super aggressive and it works well.

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P.E. Metallurgy, Plymouth Tube