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How do you know it's electropolished?


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March 18, 2022

Q. Hi there
I am working as an intern in a company that produces medical instruments. I need to get descriptive information about the machine-equipment for electropolishing process validation, its features and critical parameters in the process.
I would be very grateful if you could help me with a task that may affect my internship.

Best regards


March 2022

A. Hi Bahar. In addition to what you read on this thread, you might also want to search the site for "validate passivation" as well as "validate electropolishing". Electropolishing is more than just passivation, but one of its aims and accomplishments is passivation.

Luck & Regards,

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

Closely related Q&A's, oldest first:


The FDA auditor said "How do you know your electropolishing process is working?" My client comes to me for help. I am putting together a protocol for validating their electropolishing of 300 series stamped metal parts. Does anyone know of a standard or procedure for evaluating the effectiveness of deburring by electropolishing? Measuring the surface finish is straight forward, but any help there would be appreciated too.

Paul Vernon


A. If it were me, the first thing I would do is consult all the ASTM specs and see if anything specific to FDA materials can be found. There are a LOT of ASTM specs; for example, there is an electropolishing spec just for surgical implants; there may be one specific to FDA inspected equipment. If I found nothing, then I'd check all the ASTM specs for electropolishing. If I still found nothing, then I would say "Huh?" to the inspector without fear of embarrassment.

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


What is the end use of these electropolished parts? Components for a food mixing machine, surgical instruments, parts for an artificial hip joint?

I think the effort to document the process depends on how critical is the application. Electropolishing is good for removing nooks and crannies where micro-organisms can hide, and just as good for creating a beautiful item or one that is easy to maintain.

The minute that you know more about a subject than anyone else, the phone rings. It is usually someone that wants to put you on an ASTM committee to write the specification.

tom pullizzi animated    tomPullizziSignature
Tom Pullizzi
Falls Township, Pennsylvania


Unless you can talk your way out of any inspection, I think that you will have to develop some type of visual or microscopic inspection criteria. I have spent a lot of hours looking, usually with a scanning electron microscope, at medical devices to evaluate the effectiveness (or lack thereof) of electropolishing and etching processes. You are not alone in searching for adequate and reliable checks on these processes.

If the purpose of the process is deburring, some simple measurements of protrusions on the critical surfaces may suffice. The values for acceptance/rejection, obviously, will depend on the application. The inspection method will depend on the size of features to be measured.

Ted's answer about checking all standards and specifications is good place to start. I do not recall seeing any references to verification testing, but I haven't reviewed all of those documents.

larry hanke
Larry Hanke
Minneapolis, Minnesota


Hello, Paul:

Please look up our web site; you will find there our seminar program which includes specific details on ASTM specifications, ISO certification, and FDA validation.

We believe we can help you select from the available methods the best procedures for validation. We can give you some trade references from companies which have used our services.

You would be welcome at one of our programs. We're in Charlotte, only a few hours drive away!

With best regards,

Ed Bayha
Metal Coating Process Corporation - Charlotte, North Carolina

Ed. note: This is a very old posting;

Definition of Satin Electropolished


Q. I am a Validation Engineer working for a Biotechnology firm that is in the process of a large buildout that will make it the largest Biotech Facility in the world. My position is to validate all of the mechanical systems on this new site. We are required to check and validate that certain Ra finishes on parts, piping, valves, and equipment meet or exceed certain minimum Ra finishes. I came across a term that described a Stainless Steel finish as "Satin Electropolished". Can you explain or provide a definition of Satin Electropolished?

Robert Kology
Validation Engineer (Biotech) - Wakefield, RI, USA


A. Well the typical Ra for e.p. sst is 4.0 to 16.0 Ra micro-inches. The satin finish is the higher Ra, about 10 to 16 Ra.

Hope this helps!

Jeff Swayze
- Kelowna, BC, Canada

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