Got to ask what are you driving Year, make, model. Cause anything near new should not rust out. Emission devices are covered by an extended warranty longer than the rest of the car. If the fuel tank is leaking and it is near another thing like a vacuum lines to the tank that could also be covered.
PS e-mail me with the info that way I can do a little research.
See My jeep was a 94 a couple of months ago the Catalytic converter went bad. Just a couple of weeks ago I found out It could have been covered by Warranty.