Subject: Can Electropolishing be easily done in Home Workshop?

From: Lionel Titchener <[email-masked]>
Date: 6 Jun 1996 21:29:22 GMT

Most of what we manufacture is from 303 stainless steel, and polished by 
hand.

Has anyone put together an electropolishing setup, what is involved in 
doing this process.

Lionel Titchener

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From: [email-masked] (Robert Galloway)
Date: 7 Jun 1996 10:19:20 -0600

>Has anyone put together an electropolishing setup, what is involved in 

I've done a little electropolishing, mostly of chrome-cobalt alloys but 
some SS.  I think for different alloys the pro's use different modifiers 
in the electrolyte.  I used pure, concentrated phosphoric acid.  I don't 
think there's a significant minimum current density, the rate of action 
just goes down with the density, within reason.  I used a battery charger 
as a DC current source and SS for the cathode.  You make the work the 
anode as I'm sure you already know.  

You didn't mention the size of piece you'd want to polish or the number.  
If I were you, I'd get some phosphoric acid,  (Insert usual precautionary 
statements regarding acid, it's pretty tame stuff), grab an available DC 
power supply and experiment.  If you're going to do it as a production 
process you might eventually want to check out the equipment from a 
plating supply outfit.

rhg

BTW, the acid rapidly turns from water clear to green.  The green doesn't 
reduce the effectiveness.  The stuff remains effective for a long time.  
Also, phosphoric acid has low vapor pressure so it doesn't dry out 
rapidly or corrode everything in the shop.

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From: Robert Bickers <[email-masked]>
Date: 9 Jun 1996 18:07:12 GMT

>process you might eventually want to check out the equipment from a 
How well does this polish, really bright, matte, will "as cast" surfaces polish up or does one 
smooth the surface out first? How big a battery charger? How close do you place the anode to 
the cathode? Will this work in aluminum? I suppose we should come up with a standard object so 
we all talk about the same thing. Say 2"X2" X2" Is there a recommended amp/sq. in.? How about 
suggested reading? Thanks Bob

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From: Lionel Titchener <[email-masked]>
Date: 9 Jun 1996 20:04:32 GMT

(snip)
>You didn't mention the size of piece you'd want to polish or the number. 

(snip)

The parts are made from 8mm diameter 303 stainless steel. Turned to a cone 
on one end,with a 1.5 mm hole. Then drilled 6mm diameter the other end  
about 45mm deep. Made in batches of 200/300 at a time and barrelled in 
ceramic media for final deburring. Polishing at present is done by hand 
with felt wheels and stainless steel polishing compound. (Hyfin from 
Cannings)

Electropolishing is being considered to to save the time and mess of hand 
polishing.

I am interested to hear experience of others with electropolishing, and 
costs involved to purchase the equipment to carry this out.

Lionel Titchener

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From: [email-masked]
Date: Sun, 09 Jun 1996 23:21:15 GMT

Lionel Titchener <[email-masked]> wrote:

(snip)

>Electropolishing is being considered to to save the time and mess of hand 

On these parts use about two amperes at around 12VDC.  Positive is
connected to the work.  The electropolishing will remove burrs and
generally make the parts very shiny.  It will also passivate the
surface when the polishing is done.  Parts can be electropolished in
parallel, but leave a couple of part diameters between adjacent parts.

>costs involved to purchase the equipment to carry this out.

You can use any DC power supply.  Constant current control is best,
but any supply will work.  The cost is related to the power.  

For what you describe, a small 12 VDC supply from Radio Shack would
work for single parts, but for multiple parts and continuous duty,
more rugged power supplies are required.  I have built
electropolishing supplies for some of my customers for special
applications.  I have made supplies that will provide 30 A to 100 A
continuously 24 hours a day, 7 days a week, but they are expensive.  

McMaster Carr has some 15 Amp supplies that look like they would work.
Get a DC supply with adjustable voltage.  For typical applications,
you can use about one ampere per square inch of surface.  Lower and
higher currents can work with experimentation.  

J. M. Stuart

Engineer / Inventor / Patentee

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From: [email-masked] (philip evans)
Date: Mon, 10 Jun 1996 02:49:19 GMT

>Engineer / Inventor / Patentee

You've been patented?

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From: [email-masked] (Clhuprich)
Date: 10 Jun 1996 15:32:30 -0400

Per the Machining Data Handbook for 300 series stainless:
Phosphoric Acid, 100 amps/sq. ft., 122 degrees F for the bath.
  Material removal rates of .0005-.0015"/min ---

Cliff Huprich

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From: [email-masked] (T Wish)
Date: 12 Jun 96 04:51:13 -0700

I'd like to know too!  There are some pastes available for stainless 
steel made by a Company called Avesta.  There are also chemical 
formulas (HF, HNO3, Water, and maybe HCl) alluded to in the ASM 
Metals Handbook on Cleaning and Finishing.  Most chemicals supplied 
by vendors are proprietary.  Chemical constituents as those mentioned 
above need ventilation, nuetralizers and plenty of air!  HF of course 
will eat through your skin and has its own precautions.

Tom

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From: [email-masked]
Date: Sun, 16 Jun 96 20:58:09 -0500

>Has anyone put together an electropolishing setup, what is involved in 
 
Try adding some glycerine to the phosphoric acid that some one else mentioned.
The glycerol will make the surface have a shiny finish. Try variuos current
densities to get the right kind of finish and penetration into holes or
crevices. Does not take mush experimentation to get it right,