Heating anything up to an extreme temperature will alter it some how. However, that "extreme temperature" is variable and subjective, depending on the substance.
However, your biggest problem here is that you want to believe it is possible for a "carbon based life form" to have such concentrated acid for blood that it can "melt" through 2 feet of re-enforced metal in a matter of minutes but be great for a life system.
Also, it depend on what kind of acid they (the writers) wish to say they used. There are 2 main categories of acids, Lewis Acids and Bronsted Acids.
The traditional acid, Bronsted Acids (virtually every chemical reaction can be considered a Lewis Acid-Base reaction). Anyway. These typical "Bronsted acids" (donation of a H+ ion) occur in solution, typically water. Due to the auto-ionization of water (water is both an acid and base) there is a limit on how concentrated a acid can be, in water. And while I am not to up on industrial chemicals, I am pretty sure there is no typical acid in solution that can eat through a couple of feet of re-enforced metal in such a short time. There are some acids that probably could, but they would most likely be gases, I believe.
And so, what do you get when you heat water up (since most typically acids, the only acid these genius movie writers know of)? Steam.
So, you can do a home experiment. Vinegar is a acid, a typical acid in solution. When you introduce it to extreme heat and it boils, what happens. What are you left with? Is it still an acid? Are the majority of typical Bronsted acids even acids unless they are in solution?
And so to truly answer your question, do not try and apply real science and logic into trying to understand what happens in movies, as it is virtually never real science and logic.