Water damaged / rusted Morgans (how to restore)

I recently picked up a few silver dollars from a hoard that was damaged when a water pipe leaked on them (possibly for quite some time). Most appear to have excellent detail, but the unsightly rust spots or corrosion put them in the "cull" price category.

I was thinking this would be a good group to try a few restoration techniques out on. Don't start an all caps angry reply yet - I'm not planning to acid treat or whizz them!

What would you recommend? I've got an ultrasonic appliance I use for cleaning my eyeglasses - would short runs in there with tap or distilled water be a place to start? Or, do you think acetone would be the ideal way to remove rust spots?

Since I only have $18 apiece into them, I would rather try to bring these back into collectability than to damage a more valuable coin down the road learning the same techniques.

 

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A few more "before" pictures:

 

I would start with the least intrusive way possible. Maybe a soak in distilled water. Then move up to acetone. The ultrasonic may work but I wonder what kind of damage is underneath those spots. At $18, I'd try all three. Why not?

 

It actually looks like a iron pipe leak dripped on them and mainly a surface stain. I think your best bet is to go the acid dip, but dilute it 1 dip : 10 water, so you can watch and yank the coin out when at an end point, rinse well. With luck, the iron might come off. The dip if done lightly has a chance to retain some original cartwheel.

If it , nor nothing else helps, phosphoric acid ( Naval jelly of Rust remover) might do it, but it will give a duller surface.

Yes,First try water , soapy water, acetone or 90% isopropyl alcohol from Walmart medical area. Rinse well.

Jim

 

How long would you soak in distilled water? I'm worried about causing more rust rather than removing what's there.

I tried an ultrasonic vibe treatment on one coin (the 1886 (p) that appears to have some chemical residue between 10:00 & 11:00 on the obverse). Less than 5 minutes was enough to remove about 60% of the rust, but it seems to have made the fields markedly duller:

 

Unless it is a silver covered steel fake, I would not think any more would appear. There really should be no rust on silver dollars unless it was a metal contaminant. Neither silver nor copper has a colored compound like that. IMO. Jim

 

I would try melting them and buying new ones.

 

Doesn't copper react with water by forming greenish tarnish / verdigris? And I thought silver formed silver sulfide from even the trace amounts of sulfur found in the air (or distilled water)?

 

Yes, but the orange-brown color shown on the coins is none of those colors. Jim

 

I would save melting for the last resort myself, and I own a kiln Jim

 

Whatever you try, please post the results. Include the method tried. Thank you.

 

Looks like the "acidic" rust dripping on the coin obverse/rever has already done metal damage. Bonnet hair end / Hair V and above the date and the reverse looks like a piece of the iron is still there on right wreath. The Brown will probably mostly come off, its the black that is doing/done its damage.
Don't think anything will have a good out come but good luck anyway good experiment

 

I'm thinking the coins were stored in 2X2s with staples and moisture over the years, turned the coins ugly. I would try a weak dip on the worst one and see the results.

 

Another 10 minutes of ultrasonic cleaning with a few drops of mild soap (without any abrasives) led to this result (about 90% of the rust removed, but the chemical stain / corrosion spot looks worse without the rust to hide it).

 

I don't understand these cleaners. What keeps the coin from being rubbed in the process?

 

Most devices intended for jewelry use a soft plastic holder, and even these plastics may have a Moh's hardness rating around silver and for sure gold and can produce fine rub, which jewelers can polish. But jewelry and numismatics goals are somewhat different. I do not use mine for uncirculated coins. Jim

 

The physical contact is from water instead of a rougher surface like a brush or cleaning cloth. Even when laying down flat on a surface, there is water caught between the surfaces and any vibrating parts. There's still some friction on the rims, but, as desertgem mentions, the plastic liner prevents metal on metal rub (if used, which I did on the first cycle, but I removed the plastic cage for the second cycle).

 

Even if that's true, any abrasive bits shaken loose from the coin (or left over from things you've cleaned previously) can get caught between the coin and the surface, and leave their marks. If I were going to try this, I'd be suspending the coin with plastic tweezers or a soft plastic net.