I have welded my first patch panel on a lower fender piece that was rotted out. I was having problems with my MIG welder using .30 wire and keeping it from burning through the panels. I carefully patched this panel (sorry I know its not the right way) but Im afarid that I might of left pinholes in between the spots. When I grounded the edges down I noticed that many of these pinholes where covered up by the grinding but I know theres still some left. My question is If I shoot a couple coats of Epoxy primer will it seal these pinholes? also there seems to be some dark burnmarks in between the tiny seems it it important to clear this out before applying the epoxy? if so what do you guys recommend?