Acid Armor

A magical force surrounds and protects the caster, as part of this protection you and your gear in Acid. For the duration of the spell you gain 5 temporary hit points. When you still have the temporary hit points and if a creature makes a successful melee attack the creature takes 5 Acid damage. 

At higher level

When you cast this spell using a spell slot of 2nd level or higher, both the temporary hit points and the cold damage increase by 5 for each slot