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topic 4564

Electropolish 4340 Steel?


I have been tasked to help our customer with a problem part. We manufactured a prototype part from 1" diameter 4340 steel. It has a tapered bore thru the ~ 2.20" length and has a series of .017" wide slots running lengthwise most of the length of the part. When you look thru the part it looks like very fine "fins" along the I.D. The Slots were wire EDM'd and the part was subsequently Ion Nitrided and "Steam Treated" for wear resistance and corrosion resistance. Problem is, the surface finish in the slots is too rough and snags the yarn which must pass thru the part (very fine fibers). I can stand opening up the slots by only ~ .001-.002 and thought about using the help from a photochemical etching guy but he does not know how to remove the "Steam Treating" (oxide) without damaging the part.

Any ideas on how to A. remove the oxide , or B. improve the surface finish in the slots in some other way? C. Can this part be electropolished (selectively?)

Thank you!


Jim Brang
West Melbourne, Florida, USA


The best way to approach this problem is with a "chemical polish". It is non-electrolytic and produces excellent results on mild steel. It is available from several sources.

Dan Weaver
- Toccoa, Georgia



I don't believe chemical polishing can handle that job. Our company has electropolishing solutions for steel. We also have some experience with 4340. Please contact us via our directory listing on this web site.


Ed Bayha
Metal Coating Process Corporation - Charlotte, North Carolina


I know that a company in Texas has very good luck electropolishing the bores of rifle barrels (mostly 4140). There shouldn't be too much difference between 4140 and 4130. Good Luck.

Howard Bailey
- Flagstaff, Arizona

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