Acidic Blade

As part of the action used to cast this spell, you must make a melee attack with a weapon against one creature within the spell's range, otherwise the spell fails. On a hit, the attack deals damage as normal, except that the entire attack  deals acid damage instead of its normal type. The creature must also make a Dexterity saving throw or take 1d8 acid damage at the start of its next turn. 

 At 5th level, the melee attack and secondary damage each deal an additional 1d8 acid damage to the target. Both damage rolls increase by 1d8 at 11th level (2d8/3d8), and 17th level (3d8/4d8).