I don't really see the Fire- type in it. I almost think it would be better as Poison/Dark, but who knows, maybe it will evolve into something with flames or a fire salamander (Which have poisons that sting really bad and feel like fire).
It's Ability is very interesting, but will other Pokemon get it is my question.
I feel like it's part fire partially for the same reason Charmander is - you know, the legend about salamanders living in fire?
Also corrosion is a pretty burn-y aspect. Acid burns yo.