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topic 4763

Electropolishing pickled 316L tubing


(2000)

Prior to electropolishing, we are pickling 316L tubing (approx. 1" x 0.080" O.D.) for about 1 hr - 1 1/2 hrs in a 2%HF/21% nitric acid solution.

When I electropolish the tubing, I am having problems with uneven polish and a severe pitting of areas of the I.D. of the tubing. I'm not sure if this is a result of electropolishing (incorrect fixturing/parameters) or a result of too much dwell time in the acid pickling solution.

Also, at what point would hydrogen embrittlement become a problem?

Dave Chuidian
- California [please do not contact privately]


31 March 2000

Hi Dave ,

Why are you pickling prior to electropolishing ? if the Electropolish solution is worth a damn it should be taking care of weld marks "etc" , if its for any other reason then its actually working against the Electropolishing solution .

I will be in California starting 10 april , perhaps we could meet & discuss your problem ?

The most probable cause of the ID pitting is the etching as unless you have internal anodes the Electropolishing solution will not be working on the interior of the tubes .

The pickling time you are using is excessive in my opinion

Regards

John Tenison-Woods
John Tenison - Woods
- Victoria Australia


(2000)

dear sir,

right now I am reading and actually researching about"electropolishing". I would like your opinion about electropolishing on surfaces of plastic injection moulds and dies; whether theres a possibility or process of going about it and if possible if you could give me some good references to books related to the process. also usually moulds and dies are manufactured in materials like O.H.N.S, P-20 steel,WPS , EN-series, etc.. please let me know if the process can be suited to work with these metals . regards solomon M.

solomon mordecai
- mumbai,maharashtra,india


(2001)

I was wondering if you can answer a question for me. We have been polishing the ID surface of our valves for the pharmaceutical industry for years. If we are required to have a 15 Ra ID surface finish after mechanical and electropolish, our process requires us to mechanically polish to 10 Ra and after electropolish, we will be at 15 Ra. Is it necessary to mechanically polish to 10 Ra to achieve a 15 Ra surface finish after electropolishing?

Bob Peoples
PBM, Inc. - Irwin, Pennsylvania



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