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topic 767

Electropolishing of stainless steel

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(1998)

I am interested in information about electropolishing stainless steel surfaces. Electropolishing is a "black box". I don't understand what is happening. I don't need a book, more like a technical article.

Herbert Munt
(1997)

There are several electropolishing technical articles promoting electropolishing over mechanically polishing of stainless steel. You may want to do keyword searches on: electropolishing.

All the research I've done, seem to indicate that electropolishing is capable of polishing flat stainless steel surfaces to: a Ra of 2-4 microinches, if the materials is not flat as in tubing the Ra is not as well defined. Mechanically mirror polished stainless stainless mentioned in some of the electropolishing technical paper is supposed to have a Ra of 4-10 microinches. This may be true based on some of the samples, I've seen, but our mirror polished stainless sheets have a Ra of 0.729 nanometer and RMS of 0.748 nanometer. Below a micron!

The bottom line is: it depends on the stainless steel mills quality. While electropolishing and mechanical polishing can smooth out the surface roughness. The starting substrate's surface roughness, porosity, etc. plays a big part in the final surface roughness quality.

Regards,

Michael Liu Taylor
Michael Liu Taylor
   specialty stainless steel distributor
Dallas, Texas



(1997)

Mr. Munt:
Please see our directory listing here for our contact information and a link to our web site which contains a basic description of electropolishing for stainless steel. You may contact me directly if you need further information.

Ed Bayha
Metal Coating Process Corporation - Charlotte, North Carolina


Electroplating Engineering Handbook

Hi Herbert,

Articles about electropolishing can be found in the Electroplating Engineering Handbook, edited by Larry Durney, the Metal Finishing Guidebook, and ASM's Metals Handbook. Of these, the Electroplating Engineering Handbook has the best chapter on electropolishing in my opinion. In the days before Powerpoint, AESF had a great 35mm slide show and accompanying booklet on the subject; if you belong to a local AESF chapter, a friend may have a copy. Good luck.

Regards,

Ted Mooney, finishing.com Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey


(1997)

Whenever talking about electropolishing I mention that about 10 years ago the Metal Finishing published about 8-10 articles written by DR FAUST. Try to find them-they are great. If you are not able to trace them, let me know, I have them somewhere in our library. Sara

sara michaeli
sara michaeli signature 
Sara Michaeli
chemical process supplier
Tel-Aviv, Israel


Ed. note: Sara's posting is from 1997, so that means the articles ran in about 1987+/-
(2003) -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

What are the main electrolytes used for electropolishing? (specify with metals)
Is there any other solvent (stabilizers or catalysts) mixed with electrolyte?
If so what are their functions?
What is the time required for Electropolishing?

gopikrishnan
- trivandrum, kerala, India


We've appended your inquiry to an existing thread that answers it, Mr. Gopikrishnan, in lieu of starting a duplicative thread. The answer to your questions runs about 20 pages long and depends on which metals you are electropolishing, but can be found in the Electroplating Engineering Handbook referenced above. Best of luck!

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey



November 23, 2011 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

I had read some info about Electropolishing of stainless from google and youtube.
However, they only mention using some UNMENTIONED solution liquid. What is that? Water only?

I try to find what is the "solution" used for bathing the stainless steel?
Is it sulphuric acid?
Is it orthophosphoric acid?
Is it methanolic?
This is all I found. Not sure which is correct...
Pls help.

Andrew Lok
- Singapore

November 23, 2011

Hi, Andrew.

The solution is not water, it is a very strong acid with very little water in it. It can be straight sulfuric acid, or a mix of sulfuric and phosphoric acid, or a proprietary mix designed to extend the life of the bath. Do not use perchloric acid; it is horribly dangerous. The reason people tend to not detail it may be that there are many variations, and that some are secret proprietaries, but it's mostly because the solution composition is only 1% of the issue. Temperature, current density, freedom from water, racking to preclude problems from gas pits, etc., are critical.

I would suggest that you try to find a copy of the Electroplating Engineering Handbook (it's surely in the library), which has a great 20-page intro into the various solutions available and the critical issues. After that, you may wish to consult Metal Coating Process Corporation, specialists in electropolishing; they run training courses which you may wish to attend. Good luck.

Regards,

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey


November 24, 2011

Hi Mr. Ted Mooney, P.E.

Thank you for your information.
By the way, is welding machine also DC output?
If yes, I maybe will borrow from my factory to try out.

As for sulfuric acid, I think have to heat up to 70 °C. (from google search)

Andrew Lok
- Singapore

November 24, 2011

Hi, Andrew.

Yes, a welding machine provides DC current, but not the clean well-regulated easily adjustable power you want. Best of luck, but I really don't think you will be successful at electropolishing with neither the correct equipment nor an authoritative reference. It isn't easy, and you really want everything going for you not against you :-)

Regards,

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey



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