'green' corrosion on SxS barrels?

[JB2]

On an old set I picked up a few weeks ago.  Tiny bit of green fuzz, just noticed, on each side of the ribs.  Only about 1/4" back from the muzzles.  Can I soak the muzzle in something to neutralize the corrosion from, I assume, acid flux?  If I have to split it all up, I guess I could do that now, but was hoping to avoid it.  Wanted to try to leave the remaining blue and patina on everything, and re-doing the ribs would mean re-doing the finish.  Looked over the barrels with a magnifier after I spotted this, and the only place I see is at the muzzle. 

Thanks guys
J

[jerrywh]

 Are these Belgian Barrels?  If they are you will not remove the ribs. The green says to me that they might be brazed together.

[Captchee]

 I would say your seeing   corrosion of the copper in a brazed on rib .
 If that’s the case  you will  probably destroy the barrel before you get the ribs to lift

[Daryl]

Yes - does sound like typical copper/brass verdigris - so - use a tooth brush or 0000 wool and solvent - like Hoppe's or Outers and scrub with that. Done. .

[JB2]

Thanks guys.  I agree, it does sound and look like copper/brass gunk, but I don't see any copper or brass on the end of the barrel between the rib and barrels.  Only soft solder and steel (I poked the filler with the tip of a knife and it left a little mark).  What would acid flux look like, if not completely cleaned out from the original joining process...just rust?  Either way, I'm bummed.

I have both Hoppes powder solvent, and some of the old copper solvent.  Which would be better?  I'll have to read the label on the Copper solvent, I can't remember if it dissolves bluing or not. 

Also, could some type of solvent cause this if it was left on there?  I'm just trying to figure out why I only see it on the very last 1/4" of barrel/rib.  Wondered if excess solvent may have been left on there, or it ran out with the muzzles pointed down, and not wiped off? 

Guess I'm hoping for something other than worst-case.  I'll give it another fine cleaning (with a big magnifier to try to make sure I get it all) then watch it to see if it 'grows' again.  If it does, it may make a mighty fine double-barrel tomato stake in the spring!

Thanks again

[Daryl]

Just rub it down with a gun oil to remove the verdigris - when it happens. Now that I think about it, a copper or brass removing/disolving solvent might not be a good idea.
Brass/brazing, common normally to only Belgium guns, is between and holding the barrels together via the ribs.  The "filling" between the barrels at the muzzle will be lead.
The point of a knife, if scraped/scratched between the rib and barrel (under the forend) should show if the ribs are held on with lead solder or brass. If yellow, it's brass, of course.
I would not be concerned about it.