You conjure a potent acid at your fingertips, which can corrode metal and burn flesh. Make a melee spell attack against a creature or object within your reach. On a hit, a creature takes 6d4 acid damage and, if it is wearing nonmagical metal armor or wielding a nonmagical metal shield, you can corrode either its armor or shield. Corroded armor takes a permanent and cumulative -3 penalty to the AC it offers. Armor reduced to an AC of 10 is destroyed. A corroded shield is destroyed.   If you target a nonmagical metal object with this spell that isn’t being worn or carried, you corrode and destroy parts of the object you choose that can fit within a 1-foot cube.