How can verdigris / corrosion be removed from nickels?

luckybucks

My local coin shop that I do business with got in a spectacular collection of high grad uncirculated Buffaloes.

Problem is, every single coin has verdigris on the rim, some quite severe. The face / reverse of these coins look like they were cracked out of the roll this morning. I've got my sights on the 1931S

Any help would greatly be appreciated.

Sonorandesertrat

Do you mean greenish PVC contamination? If this is the problem, try repeated acetone soaks. The problem with PVC is that it releases hydrochloric acid upon decomposition, and the acid will dissolve coinage metals other than pure gold.

If the coins are really corroded, nothing can reverse this---they will always be 'problem' coins.

roadrunner

I had an old Hallmark PF65 Lib nickel that sat in the SDB for years. The next time I looked at it there was a big 3D green spot on the obv field. Yuk. Initial attempts at 10-30% ammonia didn't do much with quick rinses. I think I finally went to 50-100% strength and let it soak overnight. Within 24 hours there was no sign of green and only a faint shadow/toning spot where the spot had been. Hallmark grading service was long gone by this time. Sent it back in for TPG grading and it came back PF65 again.

Ammonia can sometimes remove dirt, toning, etc. so start with a weaker solution. Acetone is probably safer. I've just always liked to use clear ammonia. Your green will come off with enough soaking/rinsing. It's more a matter of what the surface of the coin will be like once that verdigris is gone.

Wolf359

Just make sure you use pure acetone only.

I tried a different brand and PCGS started bouncing all my coins as altered surfaces. The problem went away when I went back to my original acetone. I assume the chemical sniffer got me.

TopographicOceans

I hope no one brings up the urine thread

MrHalfDime

"I hope no one brings up the urine thread"

Someone just did.

AMRC

Without photos it is hard to say. Corrosion usually cannot be corrected by definition since corrosion refers to the metal being degraded. If they are green from PVC, that is usually correctable. Post some photos if you can. When in doubt, send them to NCS or PCGS for conservation.

TwoSides2aCoin

MS 63 to MS 64 without PVC. This is a SWAG for the lot.

Toss in the occasional AU 58 and an MS 65 after the bath and rinse in acetone. Problem gone. May take a couple days but acetone can't hurt them.

luckybucks

Thanks everyone.

The rims are not that bad on some, ans bad enough on others that it is spreading to the rim on the obv / rev of the coin.

This set is complete from 1928 on, and all in uncirculated grades. The rest of the coins are from 1923 to 1927 are half complete. Some of the S mint coins are VERY weakly struck.

ajaan

Do not use nail polish remover. That isn't 100% acetone.

PerryHall

How were these coins stored? PVC holders? Several years ago many albums used PVC and many flips are still being made from PVC. If so, that green slime on the rims should come off with a soak in acetone. Let us know how they turn out.

ricko

Certainly sounds more like PVC than verdigris.....go for the pure acetone soak first - agitate it occasionally (and keep the container covered due to rapid evaporation).....may have to change the solution once or twice as well....Good luck, Cheers, RickO

66WhiteFBL

If they are, like you say, spectacular Buffalo's, send them to PCGS. Don't take chances with such coins unless you are sure you know what you are doing.

luckybucks

The coins were in a cardboard coin book (circa 1950's) (brown Dansco like rectangular shaped album).

The shop gave up hope on the coins and gave them net grades and fire sale prices. I snagged the '31S for $50. (would be an MS66+ if not for the corrosion on the rim).

About 80 to 90 percent of the coins would grade MS66, 67, and a few possibly MS68 if they did not have the corrosion on the rims. The luster on these coins is something from another planet.

The collection was assembled between 1955 and 1962 according to the seller. I am also eyeballing the mint marked 29's, the '30, '30S, and '34s. A few of the coins are double dies / capped dies.

I think these coins are worth buying / sending to PCGS as long as they can remove the verdigis from the rims. Any other ideas ?

Thanks so far for the insight / replies.

luckybucks

I purchased the 1936 today for the "lofty" price of $10. Other than the corrosion on the rim, the coin is easily an MS66.

I purchased that coin as a "test subject". The coins sat in coin care for about three months. I rinsed the coin in alcohol and took a woodworker's scribe and CAREFULLY chipped away the corrosion. The corrosion did not get that deep into the coin. When I have quality time, I am going to very gently burnish the rim to remove the minor lines the scribe left and the few leftover ticks of corrosion.

What is on the rim is green and black spots (a few white spots on a couple of the coins). The 1936 had all three types, covering about 20 percent of the rim.

The result (on this coin anyway) is very impressive.

I have my eyes set on the 1930 and 1930S which look like MS67 coins aside from the rims.

lkeigwin

Pictures!

As a rule, corrosion is a killer no matter how nice the coin otherwise. Tooling won't make problems go away.
Lance.

luckybucks

I will see what I can do with pics. On the 1936 (test subject coin), you would never know there was ever any corrosion.

I have a pair of soft wooden clamps to hold the coin. There are very minor (even under magnification) tool marks that I need to burnish out. Fortunately (at least on this particular coin) the corrosion did not leave any deep craters, but left a couple small ones that I was able to tool away.

It looks like the procedure will take between three and five hours per coin, so patience is needed as well as a hand steady as a surgeon, and experience with coins / metals.

If the burnishing goes well, I guess the next step would be to find another test subject (the 1923 ???), repeat the procedure, and sent it to grading and see what happens.

Edit to add: When I was in my early/mid 20's, I worked polishing molds and dies as well as removing EDM from the molds / dies.

CoinZip

<< <i>There are very minor (even under magnification) tool marks that I need to burnish out. Fortunately (at least on this particular coin) the corrosion did not leave any deep craters, but left a couple small ones that I was able to tool away. >>



Do Not burnish or tool anything..... PLEASE.

GrumpyEd

<< <i>I rinsed the coin in alcohol and took a woodworker's scribe and CAREFULLY chipped away the corrosion. The corrosion did not get that deep into the coin. When I have quality time, I am going to very gently burnish the rim to remove the minor lines the scribe left and the few leftover ticks of corrosion. >>



Almost without doubt, once a tool is used regardless of how nice the coin was it will not grade.

TwoSides2aCoin

If it's corrosion it's ED (environmental damage). And then there's Special Ed (special education).
PCGS has restoration services. You could try acetic acid, but you will NOT like the overall look or results after the corrosion is gone. White distilled vinegar will "eat nickel" up.
Just as Nic A Date (corrosive chemicals to remove corrosion ? ) NAVAL JELLY and a good bit of elbow grease (TOOL AWAY )
… will never "fix it" right for a numismatist or for the hobbyist ( okay, maybe someone will like it).
Don't wish to sugar coat or powder puff it …. So my advice on damaged goods : buy 'em cheap and enjoy 'em. If you want to fix them, they're yours.
HOW time flies when we are having fun with coins.

ricko

It would be really interesting to see your results... several photographs at different angles... good luck, although I fear your efforts will always be detectable... Cheers, RickO

luckybucks

Here is the test coin with about 1/3 of the burnishing complete. The face and back are untouched (any damage there I would leave to the pros).



Here is the face. Very nice coin and this is about average compared to some of the other buffaloes in the collection.



Reverse.

Now for the portions where the work was performed (pardon my dirty fingers, I took these pictures at work).




You can see some depressions where the corrosion once was as well as a few hairlines from the scribe.



That spot on top of the rim appears to be a dent, but it is not (not sure how this got there). For some reason, at that angle, there is a thicker spot in the rim.

What used to be all around the rim of this coin was green corrosion spots / blotches (think moldy bread). The deepest scar on the rim is about 1 / 100 of 1MM.

ricko

Hard to tell from the pictures... glare and shadows.... but looks good...not sure what that edge damage is... that is concerning. Cheers, RickO

luckybucks

Yeah, something is going on with the rim thickness on this one. It almost seems as if the metal flowed into the die in a weird way.

Looking at the coin, there is no visible pmd, but there are two spots where the thickness of the rim changes: that thick part (in the second pic) is at 8 o' clock (under the longest feather) and at 4 o' clock there is a thin part (under the chin). Also, the coin is ever so slightly out of round (using a micrometer).

In the first pic of the rim, you can see a couple of horizontal lines in the rim, those are the scribe marks and are the only ones (I took a picture of the worst parts of the rim). In the same picture, just above the lines, (and before the shadow), there is some ticks where the corrosion once was.

I have worked with various metals over the past 25 years in some form or another (restoring classics cars / tractors, mold and die polishing, metal fabrication, etc) all requiring extreme attention to detail. I feel confident working with a bare surface (like coin rims), but would never in a million years consider touching the obverse and reverse of a coin. That job is best left to the pros.

Now I need to perfect my craft at photography.