The Metals Handbook, Vol 2,"Heat Treating, Cleaning and Finishing", 8th
edition gives a couple of recipes:

#1 sulphuric acid 41%
phosphoric acid 45%
water 14%
operating temp: 170-230F
current density: 200-350 A/sq.ft.

#2 phosphoric acid 56%
chromic acid 12 %
water 32%
operating temp: 80-175F
current density 100-1000 A/sq.ft.

All percentages by weight. You might want to get a copy of the book. It
contains articles on electropolishing and every other finishing method you
could want. Copies are available on the used book sites

Randy


"DanD" wrote in message
...
I've been experimenting with electropolishing stainless steel with
limited success. I've tried various electrolytes - hydrochloric acid
(not good), citric acid (better, but still etches my part), and
Phosphoric acid (more aggressive than citric, but still does not
polish well). I have tried various current densities, but still get
the same results - light frosting (sort of like a fine bead blast
finish), but no bright polished finish.I'm using anodic polarity with
the part to be polished connected to the power supply (+) and the
cathode (also stainless) connected to the (-) terminal. I have looked
at the finishes under a microscope and can see the reason for the
lack-luster finish. I have also read several postings, etc. where
various blends of sulfuric and phosphoric acids and am wondering if
this is my problem. Does anyone have any experience with electrolytes
used to electropolish? Any hints would be greatly appreciated. BTW,
the stainless I'm working with is 303.

Thanks.
Dan