Water damaged / rusted Morgans (how to restore)

2 hour report on Acetone:

Had to refill the glass, as about half of the acetone has evaporated and was barely covering the surface of the coin any longer. Added approximately another 4oz. No major improvement, although the previously clean surfaces do look a little cleaner.

 

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If that's actually rust (and it apparently is), acetone will never affect it.

When you're doing an acetone soak, be sure to cover your container with glass or metal to reduce evaporation. (Don't use a plastic or even plastic-lined lid; acetone vapor will swell and soften the plastic, maybe enough to droop into the liquid.)

Acetone will not attack most metals. Steel containers are fine for it. Glass is a bit risky, as a broken bottle spilling all its acetone can (a) mess up polymer flooring, (b) create a serious fire/explosion risk if there's an ignition source, and (c) produce vapor concentrations high enough to be narcotic or toxic. A few ounces in a bowl, though, doesn't pose a big risk.

 

It's on my list. Is this an experiment you've actually done yourself, or is this from discussions with others who have, or just reasoning it out?

I'd welcome further comments from @Insider, who's at least hinted that he's done this before...

 

It isn't...stop.

 

Lemon juice?

 

4 hr acetone soak. Had to refill again. The last remaining acetone was hazy and no longer clear.

 

Would there be a reaction between the iron and the silver or copper that's causing the rust to adhere? Or is it probably something like calcification that can be chemically weakened without attacking the coin itself? That's what I'm hoping to find out with the acetone, in addition to seeing how long exposure affects the surfaces.

I'm adding a glass cooking tray over the top to slow down acetone loss. Good idea - Thanks.

 

For Morgan #4, I'll give this a try.

 

Acetone will only work on organic deposits.

I don't believe that an ultrasonic cleaner has been accepted as
not being harshly cleaned or not being improperly cleaned.
The ultrasonic cleaner is just going to turn these coins into melt value clean coins.

 

You have absolutely no idea what you are talking about.
The other times I have seen these similar posts, it was someone who
was selling this type of product and had zero knowledge about coins.

 

What is holding the iron oxide onto the silver and copper? These don't normally bond, so is it possible that there's an organic compound that's playing a role in the adhesion?

 

VC would not be very effective in this application. It's far too mild.

 

You did the RIGHT thing by using distilled water. That's always the safest and first thing to try in any conservation project!

Luckily, this is technically a surface contamination issue since Morgans contain no iron. That said, it is still likely to have permanently stained the coins even if the residue is removed. Another thing to consider is that residue is surely not all iron and iron oxide, there's bound to also be calcium and magnesium and traces of other common metals in it.

There are a couple of routes you can take with rust. The easiest and cheapest would probably be to add a VERY TINY bit of lye to your distilled water soaking with ultrasound. These coins are technically "goners", I wouldn't be concerned with using an ultrasonic cleaner at all.

If the lye (alkaline solution) fails to give good results, you could also add a tiny bit of EDTA (tetrasodium) into the solution. Although I'm not sure where a consumer could obtain it. EDTA in an alkaline (lye) solution will remove that surface rust for sure but overexposure will hurt the coin surface. I would keep a close eye on the whole process.

As far as acetone, as you discovered, it's completely ineffective against non-organic residues. You have metal and metallic oxide residue. Organic solvents will be completely ineffective at treating this problem.

GOOD LUCK!

 

This was effective because of the alkalinity of the "soap" (probably actually a detergent) solution. It may also have a trace of EDTA depending on the brand. It raised the pH of your solution.

 

Just came across this discussion. I'll add some thoughts later. I have already posted about:

What luster actually is and how it differs from MINT luster.
The myth about proper coin "dipping" removing any silver alloy in any degree that is enough that you can see. Yet, soak a coin in dip long enough and you will eventually destroy it; however, that's not proper cleaning.

That's a rust residue on the coin. I cannot be specific - its a dark secret - but think about what affects rust products.

 

Okay, I'll blabber, because I'm not privy to any trade secrets, and I haven't tried any of these. I'm just basing it on fairly basic chemistry.

Complexing agents like the gallon-jug stuff mentioned above chemically combine with rust but don't affect metal at all. They may not be very aggressive, though.

Acids can turn rust into soluble compounds, but can also attack metals. Some acids may be weak enough to spare metal, but still strong enough (or having other special properties) to get rid of the rust.

Reducing agents can turn rust or other corrosion back into (loose) metal. Some reducing agents are also acids.

Ionic liquids are an exotic class of materials that can actually dissolve metal oxides without affecting them chemically. Most are expensive and hard to work with, but some are dirt cheap (the one I fiddled with is made from two components, one of which is literally a major component of pee, and the other of which is literally a major component of chicken feed). I really, really must experiment more with this stuff.

 

Pee and chicken feed okay

 

I know, right?

 

I'm terminating the acetone test. After 30 hours, the rust appears to be unaffected. The fields may be slightly more pleasant to the eye (any organic material like airborne grease or dust has been pretty much nuked away).