Metal finishing Q&As since 1989

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Philharmonic tubist finds 17-4 stainless valves stick

2006

Hello,
This might not be the proper place to ask this question but I'll give it go anyway. I'm the tubist on the New York Philharmonic and I'm using a Tuba that has pistons made of 17-4 stainless steel. They are in in a casing made of brass. Here is the question. For the instrument to function properly, these valves must be tight so that when they are oiled this will create a seal. But the valve MUST be able to move up and down freely. I am experiencing pretty bad sticking problems with my valves and I am wondering if this is happening because of the stainless steel valve in a brass casing. Will these two types of different materials work against one another, or corrode one another. I believe I am getting some sort of oxidation forming after about a month because I go in and do a VERY light lapping of the valves cleaning and all is fine. In about 20 to 30 days the problem is back. I will say that this instrument is used every day and oiled every day. I've tried oils with a petroleum base, silicone base, paraffin base, Mineral oil, synthetics.. you name it. AND these products were not mixed in the testing. Is there any kind of coating that can be used to help with this situation?
any ideas?
thank you in advance for ANY help that you can offer!
Alan Baer
Principal Tubist
New York Philharmonic

Alan Baer
New York Philharmonic - USA

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2006

Very interesting problem! I have not run into this before.

I do not think you are getting a serious electrical problem between the stainless steel and the brass, but any time you put two dissimilar metals together in an aqueous media you will get SOME electrical movement. Since you are oiling the surface between the two metals this should eliminate or minimize this. It would be interesting to find out if any other tubists are having the same problem.

Brass will always form oxides and carbonates on the surface fairly easily and quickly (hence the patina on brass and bronze statues). Sometimes coatings are used on the brass to prevent this, BUT remember that any coating you put on can (and usually does) eventually peel off, causing a worse situation.

How difficult would it be to soak the brass in a solution periodically? If not too hard, you could use a citric cleaner to do this. It would usually remove the oxides and carbonates from the surface. If this resolves the situation you know that it is the brass and not the 17-4 PH steel that is the problem.

We would be happy to help you if you contact us, as a service to the Philharmonic. Interesting problem.

Lee Kremer
Stellar Solutions, Inc.

McHenry, Illinois

Our company has extensive experience machining 17-4PH and the answer is simple: it galls. Galling is a term for stick/slip sliding of material on material. This is one of the worst materials for this phenomena so it's no wonder you are experiencing issues. Brass, on the other hand is incredibly wear resistant and is used extensively for bearings (metal on metal sliding contact) so is not the problem.

Michael H. Williams
- Santa Maria, California, USA
2007