I was tapping a sterling and copper work piece when my tap broke off
in the silver. Now the steel must be removed prior to any further
hot procedures for the piece to be put in pickle.
I realize that the steel will need to rust out, because it is stuck
too tight get out with needle nose. I was- just barely- able to get
a needle nose on it, but the steel is much harder than my pliers and
killed the tips. (now I get to spend some quality time grinding and
re-dressing my plier tips- wooo hooo!) I have quite a lot of time in
the project, starting over is not really an option.
Does anyone have any suggestions for accelerating the rusting /
corrosion process- that will not injure the sterling or the
surrounding copper? I have not yet gotten to the cosmetic stage of
dressing the piece, so slight marring that can be sanded out is
acceptable.
A solution of alum, or fresh clean pickle will dissolve the steel.
Do not us used pickle as the copper in solution will coat the steel
and stop the dissolving action.
Heat and putting the solution and work in a jar in the ultrasonic
will speed the action.
Jean- Go to the canning or baking section of your grocery store and
buy a jar of Alum. Mix some alum in water, add your piece and bring
to a boil for about 1/2 -1 hour. Sonic and steam the piece after and
your steel should come right out.
Boil the piece in Alum and water. Depending on the size of the piece
of steel it should take somewhere between 15 minutes and a half hour
to dissolve the steel.
put the piece in brand new pickle and the steel will be gone in under
an hour. It has to be new or the iron in the steel will cause the
copper in solution to be deposited on the sterling.
Your first thought was in error, throw it in NEW strong hot
pickle, sparex or swimming pool acid ok, H2So4 faster. Right. Sure
you will get a copper flash but that shouldn't be a problem., and
the tap will be history very soon.
Wrong.
If she fillows your advice and uses NEW pickle or acid, there will
be no copper flash. The copper plating we all are taught to dread
that occurs if iron/steel contacts the pickle while also in contact
with our silver or gold, only can happen if there is already copper
in the solution. Using new pickle means there isn’t any copper there
to plate back onto the work.
I had similar fun when an ultra thin diamond bead reamer broke off
and jammed in a semi-precious briolette. Nothing on my bench was
working to excavate delicately enough or shove strongly enough from
the back, and almost lost my second reamer trying.
Then after a couple days I thought of sewing needles and safety
pins. They’re amazingly hard stainless steel, sharp, and cheap–and
with safety pins you even get a built in “handle.” Worked like a
charm.
BTW, I was using water while I worked since I’d jammed a diamond bit
in stone, but for you with two metals, maybe mineral oil or WD-40?
My guess is corroding anything ferrous (and the portions you want to
corrode don’t have exposed surfaces) is probably a harder road than
digging it out and patching up the damage–even if it’s divots and
not scratches.
Some silver contains copper also so it still could happen. The steel
causes a slight electrical current, which in turn causes the plating
of the copper ions that are present.
Pop it in a warm solution of alum - as strong as you can make. It
should rust out in a matter of hours. I’m always breaking drills and
taps in brass watch parts and have an alum pot permanently on my
bench!
Some silver contains copper also so it still could happen. The
steel causes a slight electrical current, which in turn causes the
plating of the copper ions that are present.
Yes there is a galvanic action but it will not plate out copper till
it is in solution, fresh pickle will not plate. Steel is more anodic
than copper or silver so it will preferentially dissolve into
solution rather than the copper.
Some silver contains copper also so it still could happen. The
steel causes a slight electrical current, which in turn causes the
plating of the copper ions that are present.
The copper has to be already in solution before it can plate out
again. What happens is that the iron going into solution displaces
the copper, forcing it again out of solution, which is
electroplating of course. Simply having metallic copper in the silver
alloy does nothing. In fact, while there is iron there, that same
electrochemical reaction you refer to will retard the rate at which
copper is taken into the solution (in the same sort of way that zinc
coating protects galvanized iron from rusting), and pickle dissolves
metallic copper only slowly anyway. So even with mixed metal pieces
of both silver and copper, if the pickle was mixed fresh, you won’t
get much copper plating at all. Normally there may be just a little
bit right next to the drill hole, and then only if there has been a
ready source of copper ions to enter into the solution. The little
bit of copper alloyed with the silver won’t do it.