1943 steelies

The plated US coins seem to suffer more than the solid and clad. I suspect the coating is not impermeable, and the core is still reacting galvanically (?) with outer conditions. 

I don't clean coins, but will if conditions offer no alternative, and there's nothing to lose. 

The top left is a nice AU with slight corrosion just right of Lincoln's chin. Top right is a protected MS with slight rust showing around the rim, and on the shoulder.

I will attempt to clean the bottom four. #'s 1 and 2 are likely not worth it, as I expect heavy pitting. #'s 3 and 4 might have promise.

I'll post results in two weeks, along with methods employed.

The thin zinc coating is, like said quite thin and is by no means chemically inert. When this protective layer is eroded through wear or reaction the underlaying steel will easily react with the oxygen through the moisture in the atmosphere.

Yes, I've noticed this with the copper plated zinc 1982 and later. I doubt they will fare much better than the 43's especially after 87 years!

An update on #1, which I didn't think had any potential.

It's coming out better than expected. There's still heavy corrosion at the bottom bust, slight pitting to the right. Probably more pitting to come at the bottom. There's about 30 percent original zinc plating, in back of Lincoln's head, and in front of his forehead.

This is really a conservation project instead of “cleaning”. Is it worth it? Monetarily, no. I have about 2 hours so far in a $0.75 coin, and haven't started the reverse, which is just as bad. 

But more to come.

A few words on conservators. I've been fortunate in knowing two, and being able to work closely with both.

The first was a teenage White Russian who's family made it to Paris in 1917. He ended up working at the Louvre as a conservator, and later came to the US as a teacher. 

The second worked  for the NYSHA as conservator for decades.

What I've learned is that there's three main points : 

1. Stop all deterioration.

2. Preserve as much as possible without any further damage.

3. Restore the artifact as much as possible to an original state without violating #1 or #2. 

I am lucky to have Freon TF in my possession. Takes years to learn how to clean coins and sometimes to even bring back original toning. I primarily use ultrasonic cleaning. With various solutions depending on alloy & soil removal requirements.

I agree it takes years to learn how to properly conserve coins. My own background is iron and steel;  I have several corroded steelies; so I figured why not try? For me, it's a learning process. Copper I'm familiar with, but haven't tried silver yet. Steel is a good intermediary, as being the most reactive. 

I'm old school, and have never tried ultrasound.

Thanks for the input, colonialjohn. One thing I've learned in this life is that nothing can take the place of experience. And that it needs to be shared. Otherwise it may be lost again, and then have to be relearned all over again. (The historian in me).

This is the best I can do with #1. (left). The pitting still renders it within the spacefiller class. I skipped #2 and went on to #3. (right).

Frankly, I expected much more metallic zinc, but there's virtually nothing left. I suspect what I thought was Zn, was actually ZnO, which is much more brittle. I'm not inclined to go further on #3 obverse. The reverse might have pitting on “E” and right wheat stalk.

These are impossible to improve once the surface oxidation takes over. I always appreciated these coins in UNC when I was a kid. JPL