Can't get at weld after welding

[pavetim]

I need to splice weld a quarter panel but after the weld I cannot get in behind it to clean it up and paint it. I can apply weld thru primer before hand but is there anything else I can do to keep the weld from rusting my new paint job since i can't get in behind it and clean it up?

 

[BillJ]

If possible, I would drill an access hole and inject Waxoyl or similar, then plug the hole.