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topic 2963

Procedure for electropolishing stainless steel

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A discussion started in 1999 & continuing through 2017

(1999)

Q. Hi. What's the best way of electropolishing stainless steel?

frank sarrazit
- sheffield


(1999)

A. Hi Frank. Your question isn't specific enough to be answerable within the confines of the forum, Frank, because explaining the whole process takes about 20 pages. Please see the chapter about electropolishing in the Electroplating Engineering Handbook; it's excellent and quite complete. But if that text isn't readily available, the Metal Finishing Guidebook, and ASM Metals Handbook Vol. 5 have pretty good introductions. If anything is unclear, please come back here and ask for clarification. Thanks.

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


(1999)

A. If you can give me more information on the specifics of what you are doing we may be able to help.

David Crocker
- Valencia, California


(1999)

A. Frank Sarrazit: Metal Coating Process Corporation holds monthly seminars on the subject of stainless steel electropolishing. The program is intended, in part, to help answer broad questions on this topic.

You can find us in the suppliers' listing on this web site. There is also a link to our own web site, where you will find an outline of the program and a schedule of future dates.

Ed Bayha
Metal Coating Process Corporation - Charlotte, North Carolina



(1999)

Q. I am trying to solve an electropolishing problem with T304SS wire (0.187" dia). We are experiencing random problems with electroplating wire shelves, wherein some of the wires come out with a "frosty" surface. SEM/EDS has not identified any contaminants, and metallography of cross-sectional samples reveals that the "frosty" areas appear to be corroded (i.e., substantially amount of metal loss re: the good electropolished wires). Is there something with the bare wire that I should look for? Thanks,

JIM CIRILLI
TESTING LABORATORY - NEW CASTLE, DELAWARE


(1999)

A. Hello Jim. What you are describing (frosty look, loss of metal) sounds like etching. I believe that the two most common causes are the current density too low and water in the electropolishing solution. But there may be other causes -- unfortunately it's always easier to do one thing wrong than everything right :-)

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


(1999)

A. Do not electroclean before electropolish, soak clean only. Look for excessive solution movement, this will break down the "viscous layer"; the magic layer necessary for EP to take place. Also if you are doing wire goods remember SS is a lousy conductor, is the article picture framing?

Hope this is helpful.

Jon Quirt
- Fridley, Minnesota



June 10, 2012

Q. Why would you not Electroclean before Electropolishing? Pardon my ignorance, but that seems counterintuitive.

Scott Merritt
- Eastman, Georgia, United States



(1999)

If Electro-Polishing is passivation, why passivate? Should passivation be completed before electro-polishing? Can nitric passivation before Electro-polishing accomplish adequate pre-cleaning necessary for electropolishing? What is the best method to pre-clean before electropolishing and what chemical, acidic or alkaline?

Mike Cochara
- Springfield, Missouri


(1999)

A. Hi Mike. Electro-polishing inherently passivates, and obviates the need for separate passivation. Prepare by alkaline soak cleaning; nitric acid is not an effective cleaner for dirt, oil, and greases.

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



(2000)

Q. Is it necessary to put a 316 SST weldment through pickling if it gets bead blasted prior to electropolishing?

Oswaldo Rangel
- London, Ontario, Canada


(2001)

Q. I have Electro Polishing Machine. I am doing the polishing work on stainless steel for home products i.e. steel glasses.

My problem is as follows:- I mix Sulphuric - 50 kg & phosphoric 100 kg. and the temp. to make water hot is 60 to 80 degrees. and the time takes around 25 minutes. But after doing all this I can't get the perfect shine / brightness on glasses.

Can you give me the solution for this whereby I can get the perfect shine and less consuming time?

Please help me in this regard. It will be my great achievement Sir. Awaiting your reply.

Regards,

Dhiresh Chauhan
- Mumbai, Maharashtra, India


October 24, 2011

Hi, Dhiresh. Unfortunately, there are about 20 pages of things you must do right, including proper cleaning, proper formulation, proper temperature, proper racking, proper agitation, proper current density, proper procedure to exclude pre-cleaning rinsewater ... which conspire to make it nearly impossible for anyone to guess which one or ones were missed. But it seems like you have a pretty good understanding of the process, so my first thought is that the shape, position, and racking of the glasses is causing trouble. Please try your best to electropolish a simple flat shape and let us know the result. Good luck.

Regards,

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



May 9, 2013 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

Q. Hello,
Somebody can recommend me how to build electropolish laboratory in my factory?

Michael Rachilevsky
- Tel aviv, Israel


May 9, 2013

A. Hi Michael. The process sequence is quite easy: soak clean, double rinse, electropolish, double rinse. But it's not easy to do right if you have no prior experience, although the Electroplating Engineering Handbook will be a big help. There are companies like the site's supporting advertiser Metal Coating Process Corp. who specialize in educating people on electropolishing, and other companies like Russamer Lab [a finishing.com supporting advertiser] who license their knowledge and processes. Good luck.

Regards,

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



Why passivate after electropolishing?

June 15, 2017

Q. If you electro-polish a part then passivate it, what good would it do?

Herb schmoyer
commercial metal polishing - bath Pennsylvania


June 2017

A. Hi Herb. One reason for doing so would be to comply with specs; there are some which require it. A second possible reason is improved corrosion resistance. Traditional thought was that electropolishing provides excellent passivation without need for further treatment, but some feel that citric acid passivation after electropolishing improves upon it. We'll wait for someone who advocates for that to make their case.

Regards,

pic of Ted Mooney
Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey
Striving to live "Aloha"


June 23, 2017

A. Herb,
Lots of folks say that electropolishing passivates stainless, but then we always have to be careful about the word "passivate", because it means a lot of different things depending on what process and what material you are talking about.

Electropolishing (or mechanical polishing for that matter) creates a very smooth surface, which is good for corrosion resistance.

A nitric or citric acid bath removes iron from the surface, which is also good for corrosion resistance.

If you remove the iron from a very smooth surface (i.e. polish followed by acid dip), then it is DOUBLY good for corrosion resistance!

But note that just one or the other may be perfectly sufficient depending on the application.

ray kremer
Ray Kremer
Stellar Solutions, Inc.
supporting advertiser
McHenry, Illinois
stellar solutions banner



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