Alexander Chalkos Bronze Disease Solution

WD40

No it will not damage it.

Soak the coin fully in WD40.
Based on the images I'd say 30 minutes or so would do.
If that's not enough then do it again.
But experiment on one or two other coins first and you will get the idea.

Having used it successfully several times, I agree with the recommendation to use sodium sesquicarbonate, soaking the coin for a few days at room temperature

Formula for sodium sesquicarbonate solution:
10.6 g of sodium carbonate (washing soda) and 8.4 g of sodium bicarbonate (baking soda) dissolved in 100 ml of distilled water

Well anything you react with the Copper might be useful to form a more stable salt that is less of a problem. Brown.edu says the following about chemical composition:

--->"The actual chemical reaction is still not fully understood, though the chemistry of corrosion has been studied for some 150 years. However, the basic understanding of the process indicates that the presence of cuprous chloride in copper alloys reacts with water to create hydrochloric acid. The acid then eats away at the bronze, and in turn reacts with the copper. This second equation produces the visual manifestation of the disease: that dreaded green fuzz. Generally, the fuzz covers pockmarks caused by the hydrochloric acid."<---

+H2O ----> 2HCl + Cu2O
2HCl + 2Cu ----> 2CuCl + H2
A basic representation of the chemical process.

There is a great presentation below for this:

http://www.crescentcitycoinclub.org...0Disease.pdf

So can you react the copper to something less horrible to deal with? Something more stable? Well notice they mention the sodium sesquicarbonate quite extensively but they also mention some fish tank cleaning chemicals as an alternative. They can have thiosulfate so you might pull the chloride off and do this:

CuCl2 + Na2S2O3 ----> CuS2O3 + 2NaCl

Thus you have choices..... Probably end up turning the coin black with the fish cleaning chemicals if you are not careful. So maybe clean out the spots and then q-tip applications into pits with drying?

Citations:
https://www.brown.edu/Departments/J...st/4867.html