Pinholes in MIG weld

I was helping my Dad weld in a patch in the center of a hood yesterday. Every now and then, we get pinholes. Yesterday, it was really bad. Trying to figure out why. This is a picture of the back side. On the top side, nearly every weld had a hole in it. We would open up the hole with a pick, and put another spot on it, and the new weld would pinhole after grinding away.

Welder is Lincoln 175 MIG. .023 ers-2 wire. C25 mix @ 12-15psi.

Two parts to the question. First, we'd like to quit pin-holing. I'm not too worried about the backside, but on the show side, we need to figure out how to eliminate this. Second, will epoxy fill these holes?

Thanks
 
Have you tried switching wire brand? I've seen some wires perform better than others. I use Lincoln wire and don't see pin holes much, if any. Occasionally I may see one or two. Any defects are taken care of with a thin application of filler to finish the grinds so the holes are filled in, or depending on the panel I'm working on, body solder. I wouldn't use epoxy as a fix though. It may 'pucker' later due to some shrinkage. Looking at the picture I would think there would need to be some filler applied to smooth the seam so the holes would be filled also.

Mike
 
We get far too many pinholes if the e coat is not cleaned up good enough. That always causes pinholes.

Maybe you are pulling the gun away too quickly, you leave the gas flowing for the second the weld is cooling to keep contaminants away. Other than that, moisture on the wire or high humidity.
 
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