Summary for electropolish stainless parameters Discussion
Stainless steel electropolishing parameters are not simple, and the thread suggests that lowering current near the end may improve the finish in some cases, but not universally. JC Irby asked why reducing amps by about a third for the last couple of minutes seemed to make parts look better and lower Ra. The reply from Luck & Regards says this is an excellent question but one that depends on the alloy, the electropolishing solution, and how the process variables interact. He notes there are many long discussions and articles on electropolish stainless parameters, especially in biomedical work where surface profile matters, but he does not confirm the trainer’s advice as a general rule. The practical takeaway is that the effect may be real for JC’s specific setup, yet it should be treated as process-specific rather than a universal electropolishing principle.
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Q. I work at a surface finishing plant that has an electropolish line that I run. Currently we mostly do marine parts of stainless steel with some aluminum here and there.
I was told by my trainer that I can get the parts to look better by decreasing the amps by about a 3rd for the final 2 or so minutes of the process and so far this seems right.
I cannot really find any information, however on how this could possibly be so I was wondering what about tinkering with the current would decrease Ra and improve the finish of electropolished stainless steel?
JC Irby
– Knoxville Tennessee
April 10, 2022
A. Hi JC. That is an excellent question! However, if you search the site for “electropolish stainless parameters” you will see well over a dozen long threads on the subject; and if you type that term into scholar.google.com, again you’ll find over a dozen articles on the subject … so it is not easily dispatched :-)
It might depend on alloy; it will probably depend on what electropolishing solution you are using (and there are many); and the parameters are probably all intertwined rather than independent. I am not sure if your trainer’s advice applies to all profiles (I hadn’t heard it) or whether only yours benefit from it.
But the biomedical industry is extremely concerned about surface profile and what it achieves, so if you are willing to spend some money behind a paywall there is probably a good amount of pretty deep research readily available on it. Good luck.
Luck & Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com – Pine Beach, New Jersey
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April 2022
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We want to maintain a healthy electropolishing solution for 316L stainless. Is it recommended that we monitor the specific gravity, percent of sulfuric acid versus phosphoric acid and iron, chromium, nickel and copper content? I think the specific gravity would change with metal content, so how valuable is specific gravity? What is the range of acceptability for the other tests? Do you change the entire bath sometimes or just part of it or none? How do you know when to change the bath?
Thanks for your help.
Ellen Mills
manufacturing – Richmond, California, USA
2005