I’m just a beginner and I hope that some may find this more amusing
than annoying.
I’m using brass rod (1/8" and 3/32" in diameter) and Stay-bright
soft solder. The work is a rolling ball sculpture in brass and wood.
All the brass parts fit together with no gaps, I get them
mechanically clean, flux 'em up and the butane micro torch does a
fine job of flowing the solder along the joint. The joints need
pliers to come apart.
After soldering, the track goes into a sodium bisulphate (aka Sparex
2) solution (1 lb sodium bi to 1 gal H20). The solution is unheated
and I thought it safe to leave overnight. When I lifted the track
the next day it just fell apart. The solder turned into a black
powder. Nice looking brass though.
The Stay-bright is a 96/4 tin/silver solder. I assume that the
pickle is dissolving the tin from the very small amounts of solder.
I guess that tin dissolves faster that the brass (zinc and copper).
Is this typical? I’m not even sure I need a pickle, just elbow
grease. But I do want bright shinny brass.
Should I switch to citric acid?
Eventually I’ll have brass track around four feet long, so I’m stuck
with long pickle times.
Thanks for the reply Judy. I have tried using hard solder with a
butane torch, but I’ve not been too successful as yet. It is a tad
under powered. The one good bond was stronger than the brass itself.
Brass, as I’ve experienced and read, is a hard metal to braze. Now,
if my track were made from silver…!
My current technique has track being supported by rod stuck in a
mockup of the real wood sculpture. There is a lot of fiddling to get
the balls rolling where you want them. Wood does have a tendency to
burn, and at brazing temperatures, the “track mannequin” caught on
fire. Hence, for now, the silver bearing soft solder.
I suspect I’ll end up in stainless steel and TIG wielding, which is
how a lot of professional rolling ball sculptors build their pieces.
It’s the journey that’s fun. or so I keep saying to myself.
I never ever leave something in the pickle over night. Well on
purpose that is. Tim left a silver casting in the pickle for a
week and it turned to mush.
Mark- If you have a torch with enough power it’s time to step away
from the Stay- bright solder. That stuff is just too weak. Too much
tin, not enough silver.
What you are seeing is electrolytic corrosion. The brass and the
solder form a battery when immersed in the pickle. The tin is the
positive pole of the battery and is being dissolved into the pickle.
Switching to citric acid will not help. You need to not leave it in
the pickle.
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…
Mark - It sounds like a fun project - but the Staybrite solder isn’t
the right thing to use. Get some welding rod and an oxygen acetylene
torch and braze the pieces. They won’t fall apart. You will use a
metal brush to clean up the smutze from welding.
IMHO - using staybrite is fine for a prototype, but won’t last. It
is a surface connection and not soldering - which is what we jewelers
call brazing.
I have left work in the pickle over night before with equally
disastrous effect.
Is the only reason to use Stay-Bright Solder is the lower melt temp?
I have never used it and only have heard it mentioned here or in my
son’s HVAC repair manuals. I use a Presto Lite torch and have never
felt the need to try butane or any of the Kitchen Torches. Not
enough heat.
I tend to not use Pickle if I can help it. I find it easier to warm
my work and then dip it in a suspension of Boric acid, Borax, and
water. I let it dry first and then I solder with Battern’s or Boric
Acid and Alcohol for flux. I have less firescale to deal with than
if I just used pickle and any fire glass comes off in hot soapy
water.
Thanks for all the replies. The answer (if indeed there was a
question) is “battery”. I created several little batteries until the
metal corroded away. How cool is that.
But I used pickle when attempting to braze/hard solder, so I won’t
use it and don’t need it for the soft solders I’m currently using. I
will reach a decision point in the next few months and will be
helped by refinements in my technique. I can’t use brazing/hard
solder as the rods to be soldered are inserted into a wooden
template. I found the brazing/hard soldering temperatures, even
easy-easy, just too high for the wood part. I have a fire
extinguisher, but really don’t want to use it!
If I do step up to the higher melting solders, I’ll need to invest
in a torch and gas mixture capable of higher temperatures. And
figure out a way to braze those rods so that the balls move as
required and I can still use wood.