Electropolishing 301 stainless steel

[grayseal]

We are experiencing problems with electopolishing .025" thick x 7" round discs of 301 stainless steel. The supplier says that water spots are the cause.
The parts are blanked on a die and then washed. The detergent is an alkaline material and is used in an industrial spay washer. Compositon by weight % is as follows:
5-10 % potassium hydroxide
5-10 % sodium silicate
10-20 % tetrapotassium pyrophosphate
5-10 % 4 Na ethylene diamate tetra acetate
After the parts are washed, they are heated in a oven at 600 degrees F for one hour. The suppier claims the electropolishing operation will not remove the spots.
Can this be possible?

 

[nbucska]

Silicate may leave a spot what the polisher can't remove
( unless it is alcaline or contains HFl -- both unlikely )

Try silicateless cleaner or treat a sample with hydrofluoric
acid.
<nbucska@pcperipherals.com>

 

[nbucska]

They DO electropolish SS. The H2O doesn't leave &quot;water spot&quot;
on SS -unless it has solids dissolved in it.

<nbucska@pcperipherals.com>

 

[Meuchel]

It is entirely possible that an electro polish operation will not remove water spots. If the surface is not clean to start, the initial process with not start etching in that area and leave an obvious defect. My guess would be that the rinsing and/or drying after cleaning is not optimal. The 600ºF dry obviously removes all the moisture, but if there are water spots on the surface, then residue has been left behind. This is common in the semiconductor industry on bare silicon. Even 18 MOhm DI water has contaminants in it which will leave particles on a hydrophobic surface.

 

[grayseal]

Meuchel,

Thanks for the response.

grayseal