I have a 2005 Blazer with a standard open door gas cap. I have developed corrosion on the body below the gas cap door.

I took my Blazer to a body shop when I noticed a bubbling of the white paint due to corrosion. The body shop sanded down the paint, removed the corrosion and repainted. The body shop said they are seeing this problem in older Blazers and they do not have a fix short of removing and replacing the whole rear panel.

Now about 10 months later, I have the corresion bubbles again, with the beginning of rust to appear again.

Any ideas how to fix it?

 

First of all, I wouldn't go back to that body shop again. This can be fixed if done properly, but you have to get all of the corrosion out of there first, not just take off the surface rust and cover it over again. That's just shoddy work.

If it were me, I would remove the filler neck and get up on the inside. Remove any spot welds that may be in the way, holding moisture between the panels. Sand blast the rust affected areas and prime with a weld through primer in the areas that were spot welded. Weld the panels back together and seam seal all overlapped areas. Then prime all exposed metal with a good two part epoxy primer and finish.