True Acid

The next time you cast a spell with an instantaneous duration that deals acid damage before this spell ends, that acid also affects objects that aren't worn or carried in the target area, dealing half damage to these objects. If the spell doesn't normally allow you to target an object (e.g. chromatic orb), you can target one if you cast this spell first.

If you roll a natural 20 on your spell attack roll, or if a target fails your spell's saving throw by 5 or more, nonmagical items that are worn or carried also get damaged by the acid, and if the creature is a humanoid, it has disadvantage on Charisma checks until it receives magical healing.

Any nonmagical weapon made of metal or wood that is affected by the acid corrodes. The weapon takes a permanent and cumulative −1 penalty to damage rolls each time it takes true acid damage. If its penalty drops to −5, or if the weapon has no more hit points, the weapon is destroyed. Nonmagical ammunition made of metal that hits the ooze is destroyed after dealing damage. If the object is a nonmagical armor or shield, it takes a cumulative -1 penalty to AC each time it takes true acid damage. Armor reduced to an AC of 10 or a shield that drops to a +0 bonus is destroyed. 

At the DM's option, objects damaged by this spell can be restored with repeated casting of the mending cantrip (one hit point per casting), or using the appropriate artisan tools.

The DM can use the guidelines in the DMG ch. 8 to determine an object's hit points.

At Higher Levels. If you cast this spell using a spell slot of 4th level or higher, nonmagical items that are worn or carried get damaged by the acid if the target fails a saving throw, even if it doesn't fail the save by 5 or more.