Ancient Coin Conservation

I don't think the idea is as much in vogue now as it used to be, but
museums in the past often protected ancient bronze coins with a colored wax coating, after they had been cleaned after recovery from ground burial.
The was has a direct contact with the surface of the coin.

Even now, I use a black canuba wax as a polish for black cars. It works really well, and hides minor scratches.
In both cases, the wax inhibits the slow oxidation of the surface underneath.

As a parallel, pure metallic sodium is normally stored under liquid parrifin or similar, to stop spontaneous oxidation from the atmosphere.

Plastic airtight coin storage capsules may be useful, but they do not suit the display needs of most museums.

It may be useful to do a google search on the various ways in how museums conserve and protect their coins.

I have used Renaissance Wax "RenWax" as curiosity. I like that it darkens a coin a bit, but to be honest, I have only used it on a few treated Bronze Diseased coins.