Have a few lap joints in my 51 Chevy project. (floor board patch panels and bottom of cab corners).
I want to prevent future possible rust so after cleaning to bare metal, as seen in Paintucation videos, I sprayed weld through primer. Then punched the holes for the spot welding.
The problem is that I jet LOTS of sparks & weld splatter and soot at each spot weld. I figure this is because of zinc & paint being burned off. This just doesn’t seem good. Spatter was so bad the large bits even burned through the Tig weld gloves I happened to be wearing at the time.
How did you do the mig spot welds with primer in the videos and avoid this problem?