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Electropolishing 304L and 316 Stainless

We weld 304L to 316 (no filler), and need to clean the weld to a mirror finish.

We're getting all of the heat tint off with HTR-30 (nitric acid & ammonium bifluoride) and electropolishing, but end up with a haze that we still have to buff off.

We're using:

* proprietary citric acid solution,
* 12VDC/10A power connected,
* Positive connected to the part (anode),
* Negative to my stainless steel cathodes,
* using a special fixture which keeps the parts about 1/8" away from the cathodes,
* the solution boils after about 1 minutes, consuming 15A,
* we've run it 30 seconds, 1, 2, 3, 4 & 5 minutes with similar results.

Ross Johnson
Manufacturer - Charleston, South Carolina
June 23, 2009

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A couple things you can try:
1.) Immediately after welding try removing heat tint with a stainless steel wire brush then electropolish.
2.) Same as above, passivate then electropolish.
3.) Make sure you wipe the discoloration off after it comes out of the passivating so it is a uniform gray color. The electropolish.
If any of those don't work it may have something to do with the temperature/cooling cycle at the heat zone near the weld.

Looking at thread #49519, I am going to try some different weld/electropolishing samples to try and replicate/resolve your issues, Cliff Kusch
electropolishing shop - North Vancouver, British Columbia, Canada