Brass Discoloration

If it's pink, you've de-zincified it. Hope that it's only on the surface. If so, you may be able to abrade the surface copper off (maybe some fine wet-dry sandpaper, followed by a couple of grades of abrasive polish) and get back down to brass.

Or maybe you'll get really lucky and someone here will have an easier solution. Good luck.

-- Ed Huntress

Ed's right , you have etched the zinc out of the surface.

If you are lucky and it is not too deep, you can use a hydrogen peroxide pickle technique to strip back the copper rich surface.

It is also a great technique for cleaning up when you burn out the zinc with a torch after silver brazing or etching it out with acid flux.

HCl is a little strong for general cleaning. I prefer citric acid or sodium bisulfate (AKA Sparex, or sold in the pool supply section under various brand names as a granular ph reducer for pool water).

Paul K. Dickman

A similar thing happens when silver-brazing brass: the surface zinc boils off leaving just copper on the surface.

A buffing wheel will restore the brass look. An automotive buffer with rubbing compound might even work though it might take a while. I've not found a chemical that will preferentially remove copper while leaving zinc.

Way cool, Paul!

H202 is available at Wal-Mart (pharmacy) for about a buck a quart IIRC.

Be careful using a power buffer on dezincified brass. My only experience with it is with brass parts that have lost their zinc from prolonged exposure to salt water, but I've found that the surface varies in hardness and it really looks like hell when you use power to cut down to clean brass. That's why I suggested using fine wet-dry. I've used that with success, even though it takes some work to do it by hand.

I'm very interested in the peroxide treatment that was suggested, however. Unfortunately, I no longer have my uncle's boat to try it on.

-- Ed Huntress

It works pretty good. I has to be hot though. When working with small stuff I heat up a cupful in the microwave.

Clean off the flux and pickle off the black scale as usual, then use this to blast off the copper.

The vinegar solution is pretty aggressive. It is worth tracking down the sodium bisulfate, but use it all the time for jewelry work so I always have it on hand.

Only mix up as much of the peroxide mix as you will use right away. It'll process a fair bit of metal but the peroxide starts breaking down the second you open the bottle and your mix will be mostly water if you try to use it the next day.

Paul K. Dickman

And remember that common drugstore Hydrogen Peroxide is only 2% in water. If you want some more serious action, you can buy more concentrated H2O2 from a chemical supply - If BATF & Homeland Security lets you... I've seen where a pool man for condos we work at buys

They use the 98% strength H2O2 as the mono-propellant fuel for those

Good link! Sadly hydrogen peroxide is not so easy to come by this side of the pond thanks to the activities of a few of our eastward facing citizens

It is 3% these days and that is all that is needed.

You can get 40% at a beauty supply house, but I have only used it for bombing gold with cyanide and peroxide.

The catalyst bed was silver. My brother was building a rocket belt during an extended midlife crisis. He was over here every week getting me to make some part or review some design. I became a sort of defacto expert in rocket belt technology.

Paul K. Dickman

The mix uses only 3% solution. Over here, that strength is sold at drug stores as a topical antiseptic.

Paul K. Dickman

I've had the same problem using much higher proportions of acid (works faster). You have de-zinced the surface. Try a scotch-bright and scrub it just a bit. It will probably clean right up.

Bruce-in-Bangkok (correct Address is bpaige125atgmaildotcom)

Did he ever manage to fly it?

Gunner

No. We got close enough to start thinking about the peroxide distillery, when he got sidetracked.

There are several people, who built one in their sheds , that are at the tethered flight stage.

Check over on the yahoo group for rocket belts, they have links to some test flight videos.

Paul K. Dickman