3m weld through primer

[tripwr1964]

I am a new welder (experience one auto floor pan replacement) and have a question regarding 3m weld through primer. I applied per directions and having a terrible time with my welds. Is this stuff causing some of my poor welds? Anyone have any recomendations regarding this product?

[Ed Heimbach]

What process are you using, are you spot welding, useing fluxcore, or what? More information is needed here. Ed.

[Hobart Expert Rock]

WELL MOST PRIMERS ACT AS AN INSULATOR.................... SOME PRIMERS THOUGH CAN BE WELDED OVER I KNOW DUPONT HAS ONE OUT.................. YOU MAY NEED TO CLEAN THE WELDING EDGE OFF ......................USE A GRINDER ETC............... HAVE YOU USED THE WELDER ON ANOTHER PIECE OF UNTREATED METAL TO ELIMINATE THAT SECTION OF THE EQUASION......................ROCK
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[P455]

I had a heck of a time with that weld-thru stuff when I did my car's floor pans. If you follow the directions, you'll end up with nasty, contaminated, splattered welds everywhere (MIG). I then tried it with just a very light coat and it worked much better, but the welds were still much uglier than without it. Weld porosity was also bad. I ended up stripping it all off and not using it. Instead I used lots of 3M seam sealer and POR-15 to seal the weld seams.

I think the weld-thru primer is more for spot-welding (like the original welds on the car) vs. MIG (GMAW), as the arc burns it away and it contaminates the pool.

Mike

[P455]

puddle, rather.