On Mon, 31 Oct 2005 16:47:01 GMT, DanD wrote:

,;Thanks Carl. Despite my efforts, I'm still doing electro-dulling! Your
,;comment about using copper for the cathode might be what I'm missing.
,;I've been using SS for the cathode. I think my lack of success is due
,;to a combination of things. Wrong cathode material, electrolyte out of
,;balance, and low electrolyte temperature. I have however played with
,;various current densities. One other thing I have learned is that by
,;using 308 stainless wire (commonly used in MIG welding) as wire
,;hangars, there must be enough of an iron content to dirty up the
,;electrolyte with a reddish-brown emission.
,;

I got into this thread late but there probably is enough iron in any
stainless to dirty up the electrolyte. 300 stainless steels are the
easiest to electropolish. The cathode material shouldn't have much
influence. You need to run these at a hellish high current density. I
used a mixture of perchloric acid, acetic acid, and acetic anhydride.
you won't be able to get perchloric acid and if you could I wouldn't
recommend it. Too easy to get into serious trouble if you don't know
what you are doing. The chances of you knowing enough about perchloric
acid to keep out of trouble are very low.

Get copies of the good books on metal finishing. There should be
enough information there to get you started.

The Metal Finishing Guidebook, ASM International's "Metals Handbook--
Volume 5: Surface Engineering, and (especially) The Electroplating
Engineering Handbook.

Also I believe there is a "Metal Finishing Handbook". It has been a
long time so that title may not be correct.

I would suggest using your 308 stainless wire. Get a notebook and
record composition of the electrolyte, temperature of bath, voltage,
and current density. You can change the current density at constant
voltage by changing the length of wire in the bath. Note how the wire
looks with time. I would suggest H2SO4 + H3PO4 for the bath. You will
need to work at a high temperature. How high? That is why you setup
the above conditions for variables. Change one thing at a time and
record the results with comments. When you are polishing wire you can
run at a high current density without heating up the bath too much
from the IR heating.

Here are a couple references:
*******************************
Electropolishing of 316L Stainless Steel for Anti-corrosion
Passivation
Authors: Hocheng H.; Kao P.S.; Chen Y.F.

Source: Journal of Materials Engineering and Performance, Volume 10,
Number 4, August 2001, pp. 414-418(5)

Publisher: ASM International

full text options


Abstract:

316L stainless steel is deemed an indispensable material in the
semiconductor industry. In many instances, the surface of the
production equipment needs to be treated for low-corrosion
passivation, good finish, weldability, and cleanliness. The process
characteristics of electropolishing meet these requirements well. The
current study investigates the effects of the major processing
parameters on the anti-corrosion performance and the surface
roughness. The electrolyte with 10% water content and a ratio between
H2SO4 and H3PO4 of 4 and 6 has been proven to be successful, showing
no corrosion pitting points on the specimen surface. The electrolyte
temperature of 85 ± 10 °C and the electrical current density of 0.5 to
1.0 A/cm2 are found to be optimal. The processing time beyond 3 to 5
min produces no further improvement. The addition of 10% glycerin
provides a very fine surface (maximum roughness of 0.05 m), while the
anti-corrosion performance is deteriorated. The results obtained are
useful for the manufacture of the semiconductor equipment.

and

****************
Source: Transactions of the Institute of Metal Finishing, Volume 83,
Number 1, February 2005, pp. 51-53(3)
********************

If you are going to dilute concentrated sulfuric acid use ice cubes to
make up the amount of water you want. Pour the acid onto the ice
cubes. The solution will be hot but it won't splatter. Wear safety
glasses even if you don't think it will splatter. Wear safety glasses
when running your electrolysis. You will get a lot of gas evolution
and that can spread solution around where you don't want it.

Google with "electropolishing stainless solutions" will get you a lot
of reading material.

Don't forget that you are working with some dangerous chemicals. Be
careful, wear appropriate safety equipment, and keep a voluminous
supply of water where you can find it without using your eyes. You
might need that skill.