I'm putting a new cowl in and an inner fender panel and need to spot weld new pieces in place. Should I use weldable primer on both side and then wire wheel where the spot weld holes are - or is this over kill?

 

That's what I would (did) do when I welded panels together.

 

I also used the primer when i replaced my fender apron. Anything you can do to prevent corrosion is a cheap investment - IMHO.

 

Why would you need to wire wheel the weld-thru primer back off? Maybe Im missing something, but isn't the point of it that you can weld right on top off it?

 

yeah, Palerder, your not supposed to wire wheel the primer off. You weld thru it.

 

I am doing the wrap up of the same thing on my 66.
I bought the weldable primer also. I will flap wheel 80 grit over the old spot welds . tape back into the fresh coat of por 15 ,14 or what ever it is and spray
both pieces in the primer. Then weld. thats why its weld thru is my guess. Hey its saturday night and I had 2 shots of cazadores and a big brown margarita i may not be that intelligible @ this moment.

 

I probably was not clear or just don't know what I'm doing. But I thought the purpose of the weld thru primers was to coat the underside of the panels that will laying on top of each other and to ensure primer does not burn off and have rust between the panels int the future.

Since I'm spot welding the panels in place I pre drilled holes on the top panel. Where I will spot weld there will be weld thru primer on the bottom panel showing thru. I know when you mig meld you need a bare metal surface (learned the hard way). I'm assuming I won't get good adhesion unless I wire wheel areas I will be spot welding.Also, I read on the can and it says it copper based and I did not think copper was a good welding surface.

Kind of like layingswiss cheese on top of piece of bread you buttered - butterwill be where holes are at. Sorry for food anology but it's dinner time.

 

You weld onto the primer thru the holes, it sticks very well. Mustang Monthly did several articles about panel /structural part replacement. Have a look at them and you may get all of your concerns addressed. good luck.

 

Here is some hints on weld thru primer. I would use the 3M brand as I think its the better quality. I have used some off brands and had trouble striking an ark due to the fact that the liquids (and lack of solids) formed an insulation. Not all weld thru primer is equil. Another problem is that it contains lots of solids, these are what conducts the electricity and if you don't shake the crap out of the can every time just bofore you spray, they seem to settle in the bottom and you get pretty much the laqueor or whatever liquid is used to suspend them. So, shake-spray-shake-spray and so on. This seems to do the best. To make the spots real pretty, I sometimes drill the primer enough to remove it so that a clean spot can be achieved. Cover both surfaces that are to be spotted. Weld on!

 

I just grind off what looks bad. I like your way though too, I probably need to practice my welding skills somemore to get a better finish.