The authoritative public forum
  for Metal Finishing since 1989
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What is this Finish

2007

Greetings; A client of ours has a product that is a stainless steel manifold. Essentially it is a stainless steel (304) tube that has a number of funnels welded to it. It is used as a dispenser for alcoholic beverages. The question concerns the finish he is after. On his previous manifolds the surface is smooth and has a matte appearance that is definitely not polished or brushed. It does not show fingerprints when handled. I have tried passivation but it really had no effect on the finish at all. Any help with this would be most appreciated.

Cheers
R.W.T.

Ronald W. Tate
- Nepean, Ontario, Canada

It could be a dozen of things, but, why don't you check with a machine shop around if the finish of their micrometers or other measuring tools look alike. If they do, it's a vapour honed surface with a thin chrome plate.

Guillermo Marrufo
Monterrey, NL, Mexico
2007

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2007

Thank you Guillermo; The finish on my calipers and T.I.R. is close to the look I'm going for but is too shiny. The finish on these manifolds looks like very smooth pewter, almost aluminum in colour. Whatever the coating is it needs to be food grade as well.

Cheers
Ron

Ronald W. Tate
- Nepean, Ontario, Canada

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Hmmmm. I'm not sure you understood the question that was asked of you. To determine the new finish, it would be helpful to measure the surface of the part for smoothness. Typically, all medical and/or food hardware needs to have an surface of 12 RMS or smoother. That means that this part must have been mechanically worked prior to maybe a chemical coating. My next question is what about the ID of the part? Does that have to be worked also.

AF Kenton
retired business owner - Hatboro, Pennsylvania
2007

If you can get a copy of the Metal Finishing Guide & directory handbook you'll find there's a chapter about identification of coatings and platings. At least you'll be able to identify the superficial metal or alloy. Then there's the issue of attaining the desired surface roughness or finish. Good luck.

Guillermo Marrufo
Monterrey, NL, Mexico
2007

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2007

Greetings Mr Kenton;

The I.D. of the tube, that which carries the alcohol, does not need any treatment other than to be clean and free of machining residue. The entire assembly is sterilized in a bleach type solution then rinsed. A local company has suggested the finish on the sample piece I sent was first passivated then dipped in a pickling solution with a pickling paste applied to the welds to clean them up. Hope this further information helps. Thank you for your help.

Cheers
R.W.T.

Ronald W. Tate
- Nepean, Ontario, Canada

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I am not an expert on coatings; however, when dealing with FDA and medical application, it is desirable and necessary to have a good smooth surface finish. About the only way to get that smooth finish is via mechanical means and mass finishing systems. It might be possible to get close using electropolishing; however, surface improvement is questionable. If you think this is the way to achieve what you are looking for, I can provide you with more details.

AF Kenton
retired business owner - Hatboro, Pennsylvania
2007