Vitrolic Blast damage?

[Delai]

Okay so my question this time is pretty simple. How much damage does the "Vitriolic Blast" eldritch essence invocation do?

By my understanding it makes your eldritch blast ACID, and ignore Spell resistance.. but does it do that by lowering the damage to 2d6 Acid damage(And then extra on subsequent rounds)? Or is it <Eldritch Blast Damage> + 2d6 Acid damage for the next X rounds? And if that's the case does it all ignore SR, or only the additional acid damage?

[Zanos]

It changes all the eldritch blast damage to acid damage and ignores SR on all of the damage. So the blast does normal damage(but is acid typed), then they take an additional 2d6 damage on each round for one round per five warlock levels.

[Delai]

Okay, I thought so but my DM seemed to think that it replaced the damage. I think I have enough to argue my case.

[Tulya]

Vitriolic Blast says that it's an extra 2d6 points of acid damage. Interpreting "extra" to refer to "instead of/replacing" would be a bit odd.