weld thru primer

[arthuy]

I have been using a zinc one for years but have seen a few you tube videos talking about copper which has higher melting points that zinc.

In theory it liquefies around the weld instead of burning off, it also suggests that these primers are intended for spot welding.

Rust coming back is something I worry about on my welding and try to cover in paint or cavity wax but when you are rebuilding some areas it isn't always possible or easy.

Has anyone used a copper based weld thru primer?

 

[corazon]

I have used a copper one before, but like you say was only when spot welding flanges. This was an actual spot welder not plug welding.
There’s tests I’ve seen that made me think they’re a fairly pointless product in general, where standard primer seems to perform just as well..

This won’t be for everyone, but my preference now is to epoxy prime inside and outside of panels just leaving the area to weld if butt welding, and if plug welding just remove the epoxy through each sandwiched hole if that makes sense.

If butt welding a closing panel I’d want to either get something weld through on the inside edge or be able to spray something afterwards through an access hole, more epoxy or cavity wax etc

Copper will definitely affect weld quality and purity

Jim