Metal finishing Q&As since 1989

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Electropolished 440-C SS is greyish black

Hi,

I have a small diameter 440-C SS bar that looks a grayish black after electropolishing. The finish callout on the drawing that was used for fab is "Electropolish Material Removal 0.0003-0.0005 inches per surface". The part diameter is 0.117"+0.000/-0.001 and it is 4". I am assuming that this was possibly centerless ground but I don't have that information yet.

I don't have any good experience with electropolishing so I am hoping that someone here can help me. Is this a normal thing for this finish?

Thanks,

Kevin

Kevin Shea
Design Engineer - Vancouver, Washington, USA
July 22, 2009

With removing that much stock, you are probably looking at an etched surface. Contact the company for the ideal parameters of the EP for your alloy and amount of removal. They may want to change your bath makeup slightly.

James Watts
- Navarre, Florida
July 27, 2009

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440 stainless steel is not so easy to polish in a regular stainless electrolyte due to high carbon in its chemical composition. We can suggest our Universal Electrolyte which electropolish ALL types of stainless steel (including high-carbon steel). The same electrolyte electropolish other metals - copper, aluminum, nickel, hastelloy alloy, etc.

Anna Berkovich
Russamer Lab

Pittsburgh, Pennsylvania

July 29, 2009