Summary for chemical polishing before electropolishing Discussion
Chemical polishing prior electropolishing is discussed as a possible pre-treatment for stainless steel, but the thread does not endorse it. Alexandre Lapointe asked whether anyone had tried chemical polishing before electropolishing because his plating shop could not get a mirror-like finish and he wanted references on electropolishing. Ted Mooney replied that mechanical polishing before electropolishing is common, but he was not aware of chemical polishing being used that way. He also pointed to the Electroplating Engineering Handbook for more information. Michael Liu cautioned that chemical polishing is very hazardous and may create local pitting that electrochemical polishing cannot remove; he added that poor mirror results can also come from the stainless alloy itself, especially higher-carbon grades such as some 400 and 440 series. Ted later noted that electropolishing is often required for functional surfaces, not just decorative mirrors, and that it produces a different kind of finish than mechanical polishing.
Q. Hi,
I’m wondering if anyone has tried to do a chemical polishing prior to electropolishing stainless steel. I’m working in a plating shop and we can’t attain a mirror-like finish with our electropolishing line. I’m looking for any books or information about electropolishing.
Thanks.
Alexandre Lapointe
plating shop employee – Quebec, Canada
February 19, 2008
A. It is common to mechanically polish stainless steel before electropolishing, but I am not aware of chemically polishing it, Alexandre. The Electroplating Engineering Handbook ⇦ this on
eBay,
AbeBooks, or
Amazon [affil link]
has an excellent chapter on electropolishing. Good luck.
Ted Mooney, P.E.
Striving to live Aloha
finishing.com – Pine Beach, New Jersey
Need quick confidential answers? $25
Need project assistance? $100/hr.
February 19, 2008
A. Chemical polishing is very hazardous, besides it may form local pitting that is hard to remove by electrochemical polishing.
There are various reasons why electrochemical polishing does not produce bright mirror finish. One of them – high content of carbon in stainless alloy (various 400, 440 alloy types).
adv.
We have developed electrolytes that can not only mirror polish various stainless alloy types, but also sharpen high-carbon steel tools and shaving blades.
Contact us for more information.
Anna Berkovich
Russamer Lab – Pittsburgh, Pennsylvania
(ed. update July, 2025: sorry, Anna has retired)
February 21, 2008
A. There really is no reason nor need for electropolishing mirror finish stainless as the chemical mechanical polished mirror finish loses its luster when electropolished. Chemical mechanical mirror polished surface Ra can achieved 1 microinch and a mirror surface close to a bathroom mirror.
Michael Liu Taylor
specialty stainless steel distributor – Dallas, Texas
March 11, 2008
Hi, Michael. While your second sentence may well be true, it doesn’t make your first sentence accurate. Although some people may want to mirror polish the hood ornament of a truck, others want the inside of a tank or a food processing surface electropolished. It may even be legally required because electropolishing, by dissolving away material, generates a finish like ocean swells whereas a mechanical finish, no matter how fine, resembles a plowed field.
Ted Mooney, P.E.
Striving to live Aloha
finishing.com – Pine Beach, New Jersey
Need quick confidential answers? $25
Need project assistance? $100/hr.
March 11, 2008
 | “because electropolishing … generates a finish like ocean swells whereas a mechanical finish, no matter how fine, resembles a plowed field”. Ted, Would you consider the mirrored finish stainless steel backs of Apple’s iPod as “plowed field” or “ocean swells”? Would you know if the mirrored stainless surface is electropolished or chemically mechanically polished?
March 27, 2008 Hi, Mike. Whatever the finishing method for the back of an iPod, it looks very good. I love the way the lettering is etched into it. I wouldn’t know by eye how the polish was achieved, only by microscopic examination. But when it comes to pharmaceutical and food handling surfaces, as opposed to music players, I wouldn’t go by looks; I would want material that was smoothed by dissolving away the outer surface rather than by gouging abrasive plow tracks into it 🙂 Regards,
March 27, 2008 Ted, I find it interesting, polishing of semiconductor wafers are done through chemical mechanical polishing and not electropolishing. How’s that for “plowed fields”? ;-)
April 1, 2008 Silicon is a different material than stainless steel and perhaps it doesn’t develop clods. I realize you don’t like this “plowed field” analogy, but it was not my invention, it is quoted from books and micrographic photos. Just as fractal analysis tells us that the fractal degree of a seacoast remains the same at any degree of magnification, in the same way, regardless of the fineness of the abrasive grain utilized, a mechanically polished surface always retains the same “plowed field” look when we examine it at a magnification commensurate with that abrasive grain size. It doesn’t matter if the final abrasive step is India Ink … examine it at the appropriate magnification and it will look just like a surface abraded with coarse sandpaper looks at low magnification because it’s the same process but with a smaller abrasive grit. Nobody here is opposed to mechanical polishing of stainless steel, which is appropriate to the vast majority of applications. But if someone claims that there is no reason nor need for electropolishing, they’re simply incorrect. Regards,
April 2, 2008 |