Should I switch to citric acid?
You've mistaken what silversmiths/goldsmiths/etcsmiths call solder,
and what the rest of the world calls solder (the rest of the world
calls our soldering, brazing.) These low temperature solders, like
stay bright, don't require, and cannot withstand, pickling, which is
generally used only after brazing (what our community calls
"hard"soldering". The use of the word "solder" for both of these
quite different procedures can be confusing. The low temperature
work simply doesn't cause the kind of oxidation that requires pickle.
There's some discoloration, but you'll find it's mostly the flux
turning dark that does that.
Warm water and maybe a little brushing, will clean that up. If it
needs more, a brass or steel wire brush, or a bit of steel wool, or a
scotch brite scouring pad (the green kitchen dish/pot scrubbing pads
are fine), or just about any light abrasive, will do it fine. So no,
don't switch to citric acid. Your soft solder joints should not be
acid pickled. Just washed clean. then any normal metal finishing
process you might desire. Note that with hard soldering/brazing,
pickle removes oxides and that discoloration, but it doesn't leave
the metal bright polished, so you'd be doing that final buffing or
scouring or other finishing operations in any case.
If you want stronger joints, though, think about switching to a
hotter torch capable of giving you a brazed or hard soldered joint.
Brazing produces a joint that's a true metallurgical bond, with the
solder being able to penetrate into the crystal structure of the
metal being bonded. The end strength is fairly similar to that of the
metal being bonded if you do it right. With your soft tin/lead or
tin/silver joints, saying the bond cannot be pulled apart with
pliers is not that different from what you'd get with a good epoxy
glue. There isn't much in the way of a true metallurgical bond. The
solders flow over, and wet, the brass, but don't penetrate enough to
matter, and the end strength is only that of the soft and weak
soldering material, not that of the much stronger brass. And as
you've found, those soft solders are much more prone to attack by
corrosive materials (and pickles are acid. Kind of corrosive by
definition.)
On the other hand, you now know how to remove soft solder from
brass...
Peter
