I'm replacing the rusted wheel arched on my jetta, now my question is on weld through primer, I've pick up a can of upol copper weld through primer. My question is do I need weld through primer on a butt weld? My plan was to grind down the weld then epoxy primer and body work over the weld. I through you only used weld through primer on flanged joints.

Thanks

I only use weld-thru on flange and lap joints. I don't see any point in it for a butt weld.