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"Electropolishing: theory, intro, need equipment"



1997

Q. 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

A. 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
^


"Electroplating Engineering Handbook"
by Larry Durney
from Abe Books
or

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(finishing.com may earn commission)

A. 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
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
^


1997

A. 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±


2000

RFQ: Hi,

I am writing to request some info. on electropolishing machines and pricing for use on 23 x 23 inch. by .0001" stainless steel sheets

Thank you

Mehdi S. [last name deleted for privacy by Editor]
- Texas
^

^- Sorry, this RFQ is outdated
     View Current RFQs




To minimize search efforts and to offer multiple viewpoints, we combined previously separate threads onto this page. Please forgive any resultant repetition, failures of chronological order, or what may look like readers disrespecting previous responses -- those other responses may not have been on the page at the time :-)



2000

Q. Anybody know about Electropolishing? Have received a number of brochures on the subject and do not understand a few of the advantages that these companies claim that this process offers:

1. Micro-inch surface improvement. What is this?

2. Means of inspection. Huh?

3. Minimal Outgassing. Sounds like something ... well you know what it sounds like.

4. Increased heat transferability. How and why? Any information would be greatly appreciated. Thanks!

Janine Beneker
Madison, Wisconsin
^


2000

A. Many of the finishing industry texts cover electropolishing, but the best coverage of the topic is probably in the Electroplating Engineering Handbook.

1. Refers to smoothness or surface profile;
2. Probably alludes to the fact that there mechanical polishing "plows" the surface and can bury contaminants in a way that electropolishing doesn't;
3.) Similarly, you'll get no 'folded over' gas pockets;
4.) Perhaps more theoretical than practical, I'd bet.

Ted Mooney, finishing.com
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
^


2000

A. Janine:

"Micro surface improvement" refers to the smoothing of the surface accomplished with electropolish. Many manufacturers are using electropolish for microbiological reasons as it quite simply gives the bugs less places to hide.

The "means of inspection" probably refers to the fact that EP will expose any defects in the material or welding procedures. Secondarily, it stress relieves the alloy by reducing hydrogen embrittlement.

Minimal outgassing would refer to the activity in the electrolyte when the part is being electropolished. Traditional EP "off gasses" and the effect can be very deleterious.

Increased heat transfer probably refers to the electropolishing of stainless heat exchanger surfaces which benefit from the increased flow rate after treatment.

Dan Weaver
a former SW Wisconsin farm boy - Toccoa, Georgia
^


2000

A. Hi, Janine:

1. "Micro-inch improvement" refers to the capability of electropolishing to reduce the Ra or surface roughness. A good electropolishing system can reduce Ra by about 50% without getting your parts out of the size tolerance.

2. Electropolishing is sometimes used as a metallographic method of inspecting for flaws metallic crystal structure. Most of this work is done on the laboratory level, but there are some industrial applications.

3. "Outgassing" refers to the tendency of the processed metal to release gaseous compounds under vacuum.

4. Electropolishing smoothes the metallic surface and simultaneously produces a re-structured surface oxide with a lower heat transfer coefficient.

Regards,

Ed Bayha
Metal Coating Process Corporation - Charlotte, North Carolina
^



To minimize search efforts and to offer multiple viewpoints, we combined previously separate threads onto this page. Please forgive any resultant repetition, failures of chronological order, or what may look like readers disrespecting previous responses -- those other responses may not have been on the page at the time :-)



Want technical know how for electropolishing

2002

Q. Dear friends,

I am a mechanical engineering student and want to start small business in Electropolishing, so can someone come up with technical know how about electrolytic solution to be used, current, type for different steels, It will be a great help to me.

Regards,

Vimal Shah
- Baroda, Gujarat, India
^


2002

A. Hello Vimal. Many of the standard electroplating texts have chapters on electropolishing, including ASM Metals Handbook, and the Metal Finishing Guidebook, but the chapter in the Electroplating Engineering Handbook is especially good.

Electropolishing does not apply to carbon steels, but to stainless steel, especially 316SS, as well as aluminum, copper and a few other materials.

Ted Mooney, finishing.com
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
^



Seeking electropolishing equipment-Used or New

2002

RFQ: We are a manufacturer of medical equipment and we need a process of electropolishing in our plant..use or new! minimum size of bath: 30"wide x 60"long x 6"deep.

Jocelyn C [last name deleted for privacy by Editor]
- Boucherville, Quebec, Canada
^

^- Sorry, this RFQ is outdated
     View Current RFQs




2003 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

Q. 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
^


A. We've appended your inquiry to an existing thread that addresses it, Mr. Gopikrishnan. But the answer runs about 20 pages long and depends, as you say, on which metals you are electropolishing, but can be found in the Electroplating Engineering Handbook referenced above. Best of luck!

Ted Mooney, finishing.com
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
^



Seeking a portable machine for electropolishing

2003

RFQ: We are searching portable machine for electropolish vessels up to 2300 liters (650 gals).

Eduardo C [last name deleted for privacy by Editor]
- Buenos Aires, Argentina
^

^- Sorry, this RFQ is outdated
     View Current RFQs




Need Electropolish Racks for small parts

2005

RFQ: I am in need of a racking system for use in a 12" x 12" Electropolish tank. The parts I will be holding are .020 thick x .200 long. Currently dipping 10 pieces at a time using alligator clips to hold them. Need a more efficient system.

Guy R [last name deleted for privacy by Editor]
Medical Device Manufacturer - Laconia, New Hampshire, USA
^

^- Sorry, this RFQ is outdated
     View Current RFQs




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

Q. 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.
Please help.

Andrew Lok
- Singapore
^


November 23, 2011

A. Hi, Andrew.

The solution is not water, it is a very strong and viscous acid with very little water in it. It it sometimes 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 as well as the critical issues. Good luck.

Regards,

Ted Mooney, finishing.com
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
^


November 24, 2011

Q. 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 [returning]
- Singapore
^


November 24, 2011

A. 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; you'll want everything going for you not against you :-)

Luck and Regards,

Ted Mooney, finishing.com
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
^

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