Back to Ganoksin | FAQ | Contact

Removing rust from an old silver coin


#1

A friend of mine recently found an old silver coin (1697) with a
lump of what looks to be rust embedded on the face of the coin. He’s
tried all sorts of things to get the lump off, but with no success.
Anyone have suggestions?

You can see the coin (and read what he’s tried so far) here:
http://www.weebling.com/coin-pages/william_III.shtml

-Spider


#2

Spider,

I would try phosphoric acid. If you are in the U.S. it is sold as an
ingredient in a product called Naval Jelly and is used to remove
rust. I don’t believe it will attack silver, but it would be simple
enough to test it on another silver item first.

Jerry in Kodiak


#3
A friend of mine recently found an old silver coin (1697) with a
lump of what looks to be rust embedded on the face of the coin.
He's tried all sorts of things to get the lump off, but with no
success. Anyone have suggestions? 

Now bear in mind, one might not like what you find underneath once
the corrosion is removed…may have a patch of pitting underneath…

Might try soaking it in household ammonia…I recently cleaned up
a silver jital that way… Time is anywhere from a few hours to a
week, depending… The solution might turn blue…so use a tongs or
something to take the coin in and out…Used a small glass bowl for
this…

If that doesn’t do it, you can try alternating with the ammonia and
vinegar or lemon juice…cleaning with soapy water between baths…

Good luck to your friend…cleaning patches like that sometimes is
like a crap shoot…

Gary W. Bourbonais
A.J.P. (GIA)


#4

Morning Spider,

I would try ferric chloride first. A couple of drops - enough to
cover the ferrous corrosion only - and wait. The ferric chloride
should not harm the silver coin just the corrosion.

If this doesn’t work the only other thing would be to mechanically
remove the corrosion. You’ll need a microscope to see what you’re
doing, a scalpel and a lubricant. I prefer a teflon-based oil called
breakfree as it has the added advantage of loosening the corrosion.
A dab of this on the surface, leave for 10 minutes and then very
carefully scrape the surface of the corrosion with the scalpel. You
should use only one side of the scalpel, not both. After a couple of
scrapes, clean the surface of the metal to see the depth of the
corrrosion and where to scrape next. Simple but effective.

I hope this works for you
Eileen


#5

Hi Spider,

A friend of mine recently found an old silver coin (1697) with a
lump of what looks to be rust embedded on the face of the coin.
He's tried all sorts of things to get the lump off, but with no
success. Anyone have suggestions? 

I don’t think the material is likely to be rust, its more likely to
be organic in origin such as blood. The method I would try is electro
cleaning which will remove the dirt without damaging the metal. The
piece is made the anode in a bath of an alkaline or acid solvent. My
own equipment is very simple and home made. It consists of a straight
sided glass jar which has a piece of springy stainless steel sheet
around its inside face. Inside this I have sprung a piece of the kind
of stiff plastic mesh that children use to learn to sew on which is
to prevent the object being cleaned from touching the metal cathode
(the stainless steel sheet). The jar is filled with a solution of
soda and the part to be cleaned is connected to the negative lead of
a 9 volt wall wart power supply by a small crocodile clip. The
positive lead goes to the stainless sheet. You can then just leave
the coin dangling in the liquid until its clean. It will fizz as the
dirt is removed. Ideally, the clip you use to attach the wire to the
coin should be stainless or some other non-reactive metal. If the
dirt doesn’t respond to cleaning in soda, you could try dilute
sulphuric acid. Cleaning can take anything frm a few minutes to
several hours depending on the kind of dirt, the strength of, or kind
of solution and the voltage you are using. Nothing is really critical
but you should just keep looking at the coin from time to time to see
how the work is proceeding. This is the method that museums use to
clean up archaelogical items or things recovered from the sea bed.

Best Wishes
Ian

Ian W. Wright
Sheffield UK


#6

Hi Spider,

A friend of mine recently found an old silver coin (1697) with a
lump of what looks to be rust embedded on the face of the coin.
He's tried all sorts of things to get the lump off, but with no
success. Anyone have suggestions?

Another cleaning option that might work is the home brew method used
to remove tarnish from silver.

Place a piece of aluminum foil in the bottom of a glass dish.

Put enough warm water in the dish to cover the item(s) being cleaned
by about 1/4" (6 mm).

Add a tablespoon or more (depending on the size of the dish) to the
warm water.

Lay the item(s) being cleaned in the dish so they contact the
aluminum foil.

Check periodically for removal of tarnish (rust).

The hi-tech version of this is the Speedbrite Ionic cleaner. One of
these might also work.

Dave


#7

Hello Spider,

The classic rust “remover” is Coca-cola by that brand. The phosphoric
acid does the trick. Perhaps the corrosion is not rust related, but
the result of exposure to something containing sulpher compounds…

The good thing is that Coke is available everywhere cheaply, and one
can drink the excess!

Best of luck on this,
Judy in Kansas, where the deepfreeze has set in. Brrrr.


#8
I would try ferric chloride first. A couple of drops - enough to
cover the ferrous corrosion only - and wait. The ferric chloride
should not harm the silver coin just the corrosion. 

If the coin is truly “silver” why would it have rust on it? Sterling
shouldn’t rust, should it???


#9

Please do not clean this coin without checking with a professional
coin dealer. No mater what method you use to clean the surface it
will most likely destroy the collector value of the piece.

Often a collector would prefer to have a dirty coin than one that
has been cleaned and some of the coin grading services will reject a
coin submitted for grading that has been cleaned.

Greg DeMark
Website: http://www.demarkjewelry.com
Custom Jewelry - Handmade Jewelry - Antique Jewelry


#10
If the coin is truly "silver" why would it have rust on it?
Sterling shouldn't rust, should it? 

If the silver is in contact with a ferrous metal and then left in an
environment where that metal will corrode, rust will adhere to the
silver. Looking at the picture sent with the original post, it looks
like that is what had happened.

Jerry in Kodiak