Q: Brake fuel lines are corroded and the car seems to be leaking gas

Brake lines are under very high pressure when your foot is on the pedal measured in the hundreds of pounds of pressure per square inch. Fuel supply lines are under pressure as well, around 40-65 PSI. The first concern is if you suspect these lines are leaking, be sure to keep away from these parts and don’t tinker with them. You could get dangerous fluids in your eyes not to mention a fire hazard if fuel is leaking. To answer your question, there is no aftermarket quick fix for leaking high pressure steel tubes.

The ONLY solution is to cut out the bad segment and replace it with new tubing. This is not an uncommon job. Once a car gets old enough, usually all the steel tubing throughout the car has to be replaced due to corrosion (there is not a single original tube on my car but my car is more than 25 years old). As noted though, it is possible in most cases to make perfectly adequate professional repairs if the damage is limited and the rest of the line is still serviceable. This can be very economic for you as well. It just depends on how much damage you have. I would encourage you to get any suspected leaks you have evaluated, particularly if fuel is leaking because such is a fire/explosion hazard. They will let you know the most cost-effective way for you to have it repaired.