Weld through primer procedures

[hosocat]

I apologize in advance if I'm asking a question that's already been answered. I did a quick search and didn't find an answer, so here goes.

When I weld my new floor pans onto the tunnel of my 73 SB convertible, I am going to prep both the tunnel and the sanded edges of the new floor pans to a shiny surface, then spray with weld through primer before I weld.

Should I spray all exposed surfaces on the tunnel and the new pans, or should I just spray weld through primer on the spots where I'm going to spot weld the pans onto the tunnel? Also, after I've welded should I then sand off all remaining weld through primer before I prime again and finish with final coating, or should I just paint over the weld through primer, or does it not matter? Thanks for tips.

[theKbStockpiler]

Weld through primers claim to fame is when you you want to protect metal that will be enclosed after you weld it. It is stated as being better than nothing. If you use regular paint and or primer it will burn off and you will have bare metal that you don't have access to.
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[raygreenwood]

[fh4ever]

there is another school of thought....I have always used seam sealer on both sides to seal the joint. However, I just bought a rattle can of the weldable primer...I thought I might just give it a try. The salesman did tell me the primer contains zinc for welding conductivity and immediately around the weld area will burn off. so I will still use the seam sealer.

[kman]

Yeah it's more than 90% zinc. Scuff it off and epoxy before seam sealing.

[esde]

I use the the copper weld through primer a lot. It is great for stacked joints, where you have two layers clamper together, that are spot / rosette welded, like the pan/ tunnel intersection. My technique is: grind smooth, clean, prime with weld through along the entire seam. Then clamp/ screw the parts, then weld in. When I can, I prime with epoxy before using seam sealer, then seam seal, then epoxy again. Whatever you can do to seal the joint, and coat the metal inside.

[hosocat]

I bought a 12 oz can of weld through primer. Our local OReilly's had it in stock for $10 a can, which seemed reasonable compared to the $18-20 I was seeing on the internet. I don't know if all OReilly's carry it. My local one has a paint center where they mix paint, so they may carry a more extensive supply of auto paint supplies.

[ekacpuc]

Just prime, let dry and then weld.

At home I use zinc rich weld through primer.

I'm a welder (get paid to do it) and everything we weld is primed with weld through primer. If you get pin holes grind the weld out and do it again. I've never had a problem.

The primer making a weld more rust prone is bs. That's why we use the stuff... To prevent rust. I'm a shipyard welder, we service the same ferries year after year and if the weld through primer didnt work we'd know... Granted primer isn't top coat so ya still have to top coat or it will rust.

Btw every weld gets tested that I make. If there where problems I'd know.

[ekacpuc]