I was getting some rust on my extended cab on the back panel behind the doors on both sides. Ground it down and repainted it, now a few years later its back and worse. So i didnt do something right. The driver side is mostly through the panel already, its only about a 3" by 8" spot. I want to get it before it gets worse. Dont have much experience with handling rust, as didnt do it right the first time. Anybody have some tips or tricks for fixing this and preventing it from happening again?

 

Places like LMC sell replacement panels. Cut it out and weld in a new one.
Ford trucks comonly rust there.

Dirt accumulates and then when it rains turns to mud, drying slowely causes the metal to rust. Without removing the mud/dirt and repairing the inside rust only the outside looked repaired when the cancer was eating it away from the other side.

The next place to rust will be above the rear wheel wells.

These are areas that don't get cleaned when the trucks get washed.

 

after you put the new panel in spray the area down good with anti battery corrosion it turns out bieng like a type of red spray paint looking stuff and then once you have a good douche of the anti corrosion spray have it painted to the color you would like, i do this to all my wheeling rigs after they accumulate some rust it seems to do me well.