Acidskin

The skin of a creature you touch turns into bright green acid for the duration. If the target creature is not willing, it can attempt a dexterity saving throw to avoid the effects of the spell. The target is immune to non-magical acid damage and whenever the target hits a creature with a melee attack, it deals an additional 1d6 acid damage to the target of its attack. If the target of the spell is wearing non-magical armor, the armor is partially corroded by the acid skin and suffers a permanent -1 penalty to AC when wearing the armor; this effect applies to shields as well. Any non-magical weapons being held or carried by the target suffer a permanent -1 penalty to attack and damage rolls. 

At higher levels: When casting this spell at higher levels, the acid damage dealt increases by an additional 1d6 for each level above 2nd. At 5th level or higher, the -1 penalty to weapons and armor also applies to magical weapons and armor. At 9th level, this spell targets all creatures within a 5 foot radius sphere centered on a point within 30 feet.