Mod Configuration

Since Copper Extension version 1.2.1, there is a GameRule called copperOxidationChance which is set by default to 1.

copperOxidationChance is a multiplier to the base oxidation chance which depends on mod version your playing. (And yeah, I know the values are high)

You can set this GameRule to 0 if you want to disable oxidation in your inventory.