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Electropolishing stainless steel tubes
December 16, 2009
Dear sir,
I am in India.
I am doing electropolishing of stainless steel tube. but I can't find good result after the electropolishing. Please suggest to me which acid I use for better smoothness and sign.
plating shop - Ahmedabad, India
^- Privately contact this inquirer -^
December 16, 2009
Hi, Jatin. Please see the Electroplating Engineering Handbook as it has an excellent chapter on electropolishing of stainless steel, including many different formulations. But many different acids have been used successfully so I would guess it more likely that your problem is in low current density, inadequate solution movement, insufficient cleaning, or excess water in the acid than that you managed to find an unworkable acid :-)
Regards,
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 Ted Mooney, P.E. finishing.com Brick, New Jersey |
December 21, 2009
Jatin, there are many different types of stainless steels and many different types of electropolishing solutions for them. The basic formulation for stainless steel is a mixture of phosphoric and sulphuric acids; the major solutions are based on sulphuric acid contents of between 15% and 60%, with between 30% and 63% orthophosphoric acid, the remainder is water. The technology is relatively easy, but you do need to know what stainless steel you are treating! There are other solutions available, but they may not be as good as the sulphuric acid/phosphoric acid mixes. By the way, it is very difficult to successfully electropolish 400 series stainless steels.
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Trevor Crichton R&D practical scientist The Pheasantries - Chesham, U.K. |
December 21, 2009
On Trevor's comments:
Many years ago, I used a proprietary solution on Jetheat which is a modified 410 SS with excellent results. I tried to use the same parameters on a friends 17-4PH and nearly ruined it.
Different solutions work better than others on certain alloys.
See if you can find the series by Charlie Faust in Metal Finishing, probably in the late 80's time frame. He was the accepted expert at that time. It will be a big help, if you can get it.
- Navarre, Florida
January 8, 2010
The results you say you get: are you talking about the inside of the tube? Usually the inner area of a tube are low-current density sites. depending of the size of the tube you can use auxiliar electrodes, if this is not possible you can use higher current density and stirring.
Hiram Gomezelectrochemistry student - GDL, Jalisco, Mexico.
January 14, 2010
I have very successfully demonstrated to a large US Corporation, the electropolishing of the ID of tubing, which is what I presume to be the nature of your enquiry.
I would like to raise a few points which might assist you with your problems. Gassing, seems always something that affects the surface of tubing. To reduce the incidence of this, short lengths can be processed vertically in the tank but should you have long lengths of tubing, then look to pumping the electrolyte through the ID during processing.
Then of course, you have to look at the parameters of your process and examine the current density to determine that your amperage is delivering what is necessary to achieve the results you are seeking
Test the efficacy of your results by looking at the chrome to iron ratio and surface profile after electropolishing.
To offer a more qualified answer we need more information regarding lengths, whether or not you are referring to the ID and the ultimate use of the tubing.
Joel Levinsohn
- Sydney, Australia