I'm not getting much action on this thread in the detailing section.

http://forums.maxima.org/showthread.php?t=469299

I need some advice on how to fix the problems especially the rust on the bottom of the door. For that, I really want to know why it is happening in the first place and how to stop it. If I sand it out, prime and paint, it's just going to come back unless I find the root problem.

 

Try to find a new door is what I would recommend. Even if the new one didn't match, you can sand it and paint it. Theres probably something wrong with the door if it is already rusting...