POR15 is a top notch product, but it is a little tricky to work with. Since it dries to a gloss finish, you need to sand the gloss off before top coating. Another product I've been hearing good things about is Zerorust. You might want to look into that one as well. I'm probably going to give it a try as soon as I run out of my POR15 stash.qweakers said:
As for fully welding the chassis, I wouldn't recommend it. You will end up with stress fractures in the metal because there won't be enough give. Your car chassis has to have some flex to it in order to stand up to the wear and tear of daily driving.