Q. I restore cars as a hobby and have heard it suggested to use a weld through primer on spot-welded joints. I have tried this and have a problem with the metal splashing out of the spot weld. This causes a weak weld and contaminated tips. I am using 20 gauge mild steel and a Miller MS-41 spot welder. Bare steel fit-up seems to be asking for future rust. Any suggestions? (Submitted by: Rob Suggitt from Unknown)

A. As far as I know, there isn't a good "weld through" primer out there. The primer is not nearly as conductive and that's why you get a poor weld and splash backs. Spot welders need good, no...great metal conductivity to weld properly. Spot welders have very little output voltage but have extremely high weld amperage. It's the arc voltage that would be necessary to bust through any primers or sealant. There are some MIG spatter sprays that might work, but I have never tried this.
I wish I had a better answer for you. Hope this helped some.