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"Procedure for electropolishing stainless steel"



Current question and answers:

December 9, 2020

Q. I am manufacturing SS flexible hose made of SS291 and 304
And i need to know the process of doing electropolishing to get mirror finish. I want to start with small tank of size 120 cm x 80

2963-1

Please anybody could guide me with the complete process.
As I am new to this field.
Thanks,
Azeez

Azeez Moiz
- Cairo. Egypt
^


December 2020

A. Hi Azeez. You need to mechanically prepare the component, then properly clean and rinse it, then electropolish it. Unfortunately, I don't know exactly what "new to this field" means; but you're not going to learn to electropolish solely from a response to your question here. You can start with the previous Q&A's on this thread, search the site with the term 'electropolish stainless', and consult the 22-page chapter in the "Electroplating Engineering Handbook" [affil. link to book on Amazon] for current density, solution concentration, and some other tips ... but it will still hard to do without knowledgable hands-on instruction.

Luck & Regards,

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


February 3, 2021

Try www.worldstainless.org website. There you can find download free booklet on electropolishing of stainless steel...

Hope it helps and good luck!

Goran Budija
- Zagreb Croatia
^




Previous Q&A's on this subject started in 1999 and continued through 2020:

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
Ted Mooney, P.E.
Striving to live Aloha
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

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
Ted Mooney, P.E.
Striving to live Aloha
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
^



1999

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


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
^



Non-uniform chrome finish on stainless steel parts

----
Ed. note: this was originally posted on a chrome plating thread, but as the story unfolds, the process in question is actually electropolishing, not chrome plating.
----

January 9, 2020

Q. Our finisher recently sent us parts with non-uniform chrome finish. The parts consist of a formed stainless steel rod TIG welded atop a stainless steel tube. Our finisher is of the opinion that the rod is not stainless steel, but we have confirmed that it is.

48052-1a 48052-1b

As seen in the attached photo, the chrome appears to have adhered fine to the tube and weld, but not to to the rod.

Any ideas how/why this might occur? Thank you in advance!

Jon Horner
employee - Bryan, Ohio USA
^


January 2020
the_dress

A. Hi Jon. Pictures can be deceiving, as the world knows from the famous gold & white dress which my son insists is blue & black. But your component looks to me like it has not been plated at all. Are you implying by "chrome finish", and by which thread you posted your inquiry on, that your finisher was supposed to nickel-chrome plate it? Or was he supposed to electropolish, manually polish, or what?

"Stainless steel" is a very broad description of the material of construction, and you should probably try to find out what types of stainless steel the rod and tube are, and to get at least a general description of what the alleged finishing process is. But personally, I'd probably retain a finishing consultant if I was in your situation.

Regards,

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


January 9, 2020

! Ted,

Thank you for your response! I did some quick checking, and you are absolutely correct - these parts are to be electro-polished.

Ironically, it is a mixed lot. Some parts have the bent rod polished fine, while others are not polished at all. We have even found one part which is electro-polished halfway across the bent rod, to just past the weld. The remainder is the unpolished grey look.

Jon Horner
- Bryan, Ohio USA
^


January 2020

A. Hi again Jon. Myself and other readers would like to help, but finishing is like anything else: We might possibly be able to assist your electropolishing shop in a small way if they told us exactly what steps they were doing and if we were 100% sure of the alloys ... but unfortunately it can be impractically difficult to try to guess what went wrong only from a picture of the end result :-(

Was the rod black before you shipped it? Did anyone do any heat treatment after the welding? Why are the parts electropolished -- only for looks, or for corrosion resistance, or for cleanability/hygiene? Can you send one unsuccessfully polished part to another electropolishing shop to see what they say and achieve? You can search the site for "electropolish stainless steel" to learn some of the basics. Thanks.

Regards,

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

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