(I tried posting this last night from home, but was probably stymied by the fact that I have changed my system date to prevent W7 from crashing. Apologies if this is a repeat.)
On another list I read (about coining), someone asked if it is possible to remove some lead solder from a gold coin. I thought of using an acid that would dissolve the tin and lead, but what would that be? Also, would any such acid leach out the alloying metal from the gold, and would that change the color of the coin?
The coin is a 2 1/2 dollar US piece, in otherwise good condition, so abrasive removal would probably not be a good option.
I'm not involved in this, but it seems to be an interesting problem, and if anyone has a workable solution, I'll be glad to pass it on (with attribution) to the OP.
responding to http://www.polytechforum.com/metalworking/removing-lead-solder-from-gold-coin-2nd-try-193323-.htm , hony wrote: Hiii friends...
Best way to remove lead solder from Gold...
On Thu, 06 Aug 2009 08:51:34 -0400, Joe wrote:
A quick bit of looking on the web suggests that
a) quarter-eagles are 90% gold / 10% copper; and
b) tin-lead solder can be removed from copper with a solution of 33gm acetic acid and 50 gm hydrogen peroxide in 1 litre of water; and
c) acetic acid WITHOUT any nitric acid will not dissolve gold
so what I'd do, if minded to do this on my own, would be to remove as much solder as possible with heating and wiping/wicking, then make an appropriate solution and watch it. Remember that common white vinegar is only 5% actice acid, so you'll have to do a bit of extra maths.
Seems like metallic mercury will remove the lead and not the gold. Years ago, as a kid I used to play with mercury. It removed the lead from the solder at the joint where the ring I wore had been resized.
Oh, forgot to mention that mercury was used for years to remove lead from firearm barrels after shooting soft lead bullets. Used to keep a bottle in my shop for this purpose.