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Help ELECTROLESS polish the ID of a small stainless steel tube. Chemistries?  

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Hi folks,

I have a question I am hoping the users of this forum can help me answer.

I would like to chemically polish the inside diameter of a 0.030" ID stainless steel tube, about 2-3" long. This piece of tubing will be used to make a length of microwave "waveguide", and so I would like to have a very smooth, clean surface with a well known initial ID.

Electro-polishing is out of the question. We've tried it with poor results because of the very small wire diameter and more complicated mechanics required. I've also tried mechanical polishing with dental floss and abrasive, and besides being tedious it didn't work so well either.

Others have suggested in the past that I purchase pre-polished hypodermic grade tubing to start with, but it is difficult to obtain small quantities of steel tubing with a 0.030" ID to begin with. I am lucky to have what I have.

What I would like to do is find an appropriate solution or solutions that can be pumped through the tube using a tubing pump. I need an actual chemical *polish* that will remove surface irregularities in addition to scale, rust and debris inside the tube.

I know there are some companies that do this, but generally they don't want small quantities of stuff, and it would be very much more convenient to do this in-house, as we have a reasonably equipped chem lab. Furthermore, lots of commerical places use proprietary chemicals, so it will be impossible to know exactly what they did in the future if I need to repeat the process.

So, I am hoping someone can suggest some chemistries to chemically (electrolessly) polish steel that I can try in-house, OR recommend a shop that will do small jobs with a relatively sane turnaround time.

Thanks in advance for any suggestions.

Daniel Koller
Researcher - Charlottesville, VA, USA

Although electropolishing is no chip shot, neither would I call it out of the question, Dan. Can your waveguide be made of copper, nickel, or gold instead of stainless steel? If so you could electroform it on a .03" diameter wire mandrel and the ID would be every bit as smooth as the OD of the wire.

Ted Mooney, P.E.  finishing.com Brick, New Jersey

Nope. It's intended to be a thermally-isolating section of waveguide. WR-3 rectangular waveguide (0.034" x 0.17") is commercially available in coin silver, but not steel. So I am using the round stainless tube as a substitute, which is already a compromise. That's why I'd like to limit the loss as much as possible in the tubing I have. We have extensive electroforming capabilities in-house, but it's not an option.

I've sent a sample off to a stainless micropolishing company in California, and they claim to have an electroless steel polishing technique. I have not gotten the samples back yet, but I understand their dip solution is proprietary. Anyone have any Idea what they use?

Thanks.

Dan

Daniel Koller
- Charlottesville, VA, USA

Ed. note: the internet is too anonymous for us to want to print replies to your closing question, Daniel.