Paint & Body Work - should i be worried?

i might be a little paranoid, but underneath where the battery sits in the engine bay my car has developed rust on the passenger side directly behind the radiator. if i had to guess the total area covered is roughly only 4"x6". it's not big, but just enough to make me wonder. i believe the cause was battery acid. i don't know anything about body work, but should it be replaced or is it not big enough to critically endanger the frame? and if i were to replace it what specifically would i be replacing? there's a little spot on the hatch too... i guess the best question would be, "When should I be concerned with the integrity of the frame, so far as rust?" thank you.

sand the rust and paint over the affected area. its probably just on the surface, but its corroded all the way through, then id be worried

clean it and paint it with that stuff por-15 works wonders on rust ( just dont get it on your hands)

ok cool, i'll try that. thanks.