I just got roof welded and after grinding the weld flush I noticed that in couple spots it did not penetrate really well. I was wondering should I have the guy go over that spot again or it will be good enough. Also I'm confused are you supposed to put body filler on the bare metal or can you put it on primer. I'm scared to put it on the bare metal because I think that some rust might start under neath it.

 

If the weld didnt penetrate through both pieces of metal then they havent reached a point of proper fusion. A good way to tell is look on the backside of the weld and if you see a where it was welded then its fine, if not then do it again. And as for the filler...just make sure you clean the burn marks off and make sure the metal has been abrated with coarse enough grit of sandpaper (Id go with 40 or 50 grit), and you can apply it directly to bare metal.

 

thanks