How Cleaning Affects Value And Eye Appeal

Neutral EDTA (I use disodium EDTA buffered to pH 7.0) won't attack metal or metal oxides or sulfides, only corrosion (metal carbonates, hydroxides, chlorides, etc). It will remove the "metal" that's in the corrosion.

EDTA and similar chelating agents are thus milder than direct acid dips, wheich tend to remove all corrosion byproducts incluing oxides and sulfides, and begin to attack the metal itself. For corroded coins, the "original surface" at the corrosion points is gone, corroded away, but the surrounding area might still be worth saving.

I've found that for a heavily oxidized bronze/copper coin left soaking in EDTA for too long, the oxide layer remains in place, but is weakened and easily dislodged (eg by touching or wiping the surface with fingers). Keeping the "original surface" of the uncorroded areas of copper/bronze coins requires patience and skill. You can't use EDTA as a "magic bath" that makes the corrosion go away but leaves the remaining surface completely undamaged.