Annealing brass discoloration?

[Bigmon]

Had allot of trouble with a rear RR pipe flange and after working it awhile I have annealed it so I can work on it a little more.
I'd rather dig a ditch than try to inlet these things.  Sometimes goes perfect, other times no so much.
Anyway, after annealing this thing  and fitting I tried buffing to clean off the black stain.
It don't wanna come off by buffing.  It is some better but still has allot of stain.
Before I takes some emery paper to it and see if that works, I thought I'd ask you experts??
Will it ever come clean or do I now have a stained RR pipe flange??
I guess after using the gun awhile it will not be noticed but when new and shinny it would be nice if everything was new and shiny??
Maybe I have discovered a nice way to make all the brass look aged??
Thanks to all

[bama]

Try buffing it with 0000 steel wool, if that does not work hit it lightly with some fine grit sand paper.

[davec2]

Bigmon,

The discoloration is coper oxide (from heating in air).  You can mechanically abrade the oxide away, but it is much easier to "pickle" it off.  The best way is with a solution of 50 / 50 pool acid (muriatic or, more correctly, hydrochloric acid).  This will work at room temperature but is best heated some.  If this type of acid is unavailable to you, drop the pipe in straight vinegar (acetic acid) over night and then dry and try to polish it.  The vinegar will work to take away to oxide layer, it just takes a lot longer.

You can also use dilute battery acid (sulfuric acid) or dry pool acid (sodium bisulfite) mixed with water.  Just don't use nitric acid....it will completely dissolve a brass part.

Acid pickling is a standard practice to remove most oxides after brazing, annealing, etc., any treatment of metals that requires heating in air.

Hope this helps,

Dave C

[Bigmon]

It helps a ton, thanks so much
I'll give it a try.

[Bill Raby]

https://www.riogrande.com/product/rio-pickle-for-non-ferrous-metals/5010233gp

   Try this stuff. Mix it with water and keep it warm in a potpurri pot.

https://www.riogrande.com/product/boric-acid/704096

   Put some boric acid in a jar full of denatured alcohol. Stir it up and dunk your brass parts in it before heating. Light it on fire to burn off the alcohol and you have a brass part coated in boric acid. It will melt when you heat it up and you will have a air proof coating on the metal that will hold up past the melting point of the metal. You can anneal and the oxidation will be greatly reduced. soak for a few minutes in the hot pickle solution. Brass will come out with a red color, but it will polish right off. The boric acid also makes a great casting flux.

[flehto]

I just use 220 grit paper and then go finer.....Fred

[P.W.Berkuta]

Quick method : sandpaper, Scotch-Brite, steel wool -- slower method : acid etch -- your choice

[Bigmon]

Thanks for all the help on this.
Last evening I took the brass in question and having some good old apple cider viniger her in the kitchen, I figured I try that for the nite.
As I had none of the other stuff mentioned on hand.
Got up this morn and took a look.
All the black stuff was off and floating around in pieces in the vineger.
I took a pc of well used and dull 0000 stell wool and it shined right up.
Thanks to all, problem solved.

[davec2]

The acid pickle is MUCH less aggressive than the abrasive method alone.  Abrasives are fine is the part is not to final shape or finish, but if you need to solder or anneal a nearly finished part, the pickle is the way to go.  Both Bill Raby and I are approaching this from the standpoint of being a jeweler where we don't have the luxury of using a mill bastard file and 220 grit paper to remove a little oxidation.

Glad the vinegar pickle worked...........by the way, if you ever need to clean up badly oxidized brass or bronze parts, just wash the parts with a strong detergent to remove any grease or oil and then do the vinegar trick.  As Bill says, the part will look red (copper colored) but will come right back to a brass or bronze color with a very mild abrasive (like tooth paste and a tooth brush).

[Daryl]

Beware- I had a bottle muriatic acid in the shop for something to do with my reloading - cannot remember exactly what.  After opening (cracking the seal) the bottle, then replacing the cap, all the tools near that bottle started rusting and continued until I disposed of the acid.