soldering

[omark]

many yrs ago i soldered some thimbles to a barrel and had moisture form from the heat inside the barrel and instantly rust it. what do you guys do to prevent this?   thanks in advance, mark

[smylee grouch]

Been there, done that.  Now I clean the barrel right after I do any soldering on a barrel.

[galamb]

Spray it down inside with a good dose of WD-40, just don't hit it with an open flame, it will light up if the flame directly contacts it...

[Acer Saccharum]

Wait, what temperature solder? Plumbers solder? 600F, or Silver braze 1200 F?


If plumber's solder, coat the bore with ROSIN flux, no corrode. or grease.

[omark]

OK guys, thanks for the replies. I did clean the barrel right after soldering, and the rust was there, immediately. It was plumbers solder. I'm thinking heating the whole barrel slowly and a good coat of oil or WD might be the answer.  Sure spooked me, it was a new grrw barrel and they ain't making many of them any more.  Thanks again, mark

[Acer Saccharum]

If there is any acid in the barrel, like if you use acid flux, fumes could have entered the bore, causing rust. You might want to neutralize and acid with baking soda wash or similar neutralizing chemical. Dry and grease.

[bgf]

Probably got it too hot trying to get the spot hot enough for solder to flow.  I put a barrel on the gas BBQ and soldered a solid rib on it with a propane torch (w/430dF silver bearing solder) and never had any rust inside the bore (just wiped with acetone and oiled after soldering).  I think heating the entire thing actually reduced the amount of heat focused on one spot at any one time, and may have driven the moisture out.  That barrel was heavy (1 1/8" .40), also, so heating it took a while.  A thin barrel could develop a hot spot really quick if soldering a thimble on.

[Don Getz]

Over the years I soldered a lot of underlugs and front sights on octagon to round barrels.   I always ran an oily patch down
the barrel when I waa finished.  I would also check the bore for rust over the next couple of days, but, never really had any
problems with rust.........Don

[frogwalking]

Maybe if you heated the whole barrel slower, until the entire thing was a couple of hundred degrees, then heat the solder spot on to required temp.  Perhaps I have been lucky soldering underlugs and front sights on smoothbores, but  I have not had heat draw moisture.  I have problems with rust when boiling a rust blued barrel.

[WadePatton]

Harris white flux works to prevent oxidation on the inside of the 4130 tubing I silver braze, but that the tubing is .035" wall, not BBL thickness.  It soaks off in or with water. 

MOF (matter o' fact) the flux stops temper colors from forming as well.  You'll only see them on metal near the join that wasn't fluxed. 

That white flux on those pre-fluxed brass brazing rods from the corner cowboy supply house...that's NOT the same stuff.  It won't soak off.  The brass is fine, but never use that flux on anything but plows and hitches where grinder marks are acceptable.

but then i'm brazing nebbermind...

[omark]

Thank you all very much,  ark