Please Explain Weld Thru Primer

[dibbons]

I have never seen this "weld thru primer" on a store shelf, have never seen a welder use it, and never seen anyone even speak of it or mention it. Maybe here in Mexico, the welders are behind the times?

 

[dartgarth]

It's a primer with a high zinc content that you can weld through. I find it kind of sucks for mig welding (especially long beads. It just heats up and burns off) and I really don't tend to use it for that but it's great for spot welding.

 

[Evan Dutch]

I’ve been told that it’s intended use if for doing metal work where a lap joint is involved. Let’s say you are welding in some floor pans, since these panels are quite large it can be tricky to trim them in such a way that you can butt weld them. So a lot of guys will usually overlap the two pieces. But before welding it the weld thru primer is supposed to be applied to the area that Is overlapped. Unlike a butt weld, moisture may find its way into an overlap joint and create problems I’ve heard that the weld thru primer Is a way to prevent this type of problem.

 

[R4Sedan]

Yeah, both replys are good. You can buy it at places like Eastwood, Summit, etc...

 

[Tooljunkie]

Yes, that pretty much sums it up.
Good for spot welding.
I follow up with zinc rich primer, also slows down the rust.

 

[Treblig]

It protects the bare metal from rusting until you can get around to the welding and it also conducts electrical current so you don't have to sand it of to weld. I've used it many times.

 

[Frodee]

I have been using it for years and I have said before I have put a lot of truck box sides on over the years using a wire feed welder and replaced the box sides on many trucks 3 or 4 times in a 5 year period and when I take them apart the weld through primer has still been good even around the welds.
I am not the best body man out here and if there is something better than please let me know.

 

[sireland67]

I use it on all my panels, NAPA sells it but it is not cheap, like $15 for a spray bomb can, but it does not take much to do a panel.

 

[dibbons]

Is "anti-splatter" spray the same thing?

 

[sireland67]

No

 

[clementine]

Ive tried it. Seems to clog up the tip in the can within the first 2 seconds or so. Tried shaking it, turn upside down, swearing, then gave up and welded the part thinking ill use seam sealer and primer/sealer/ base coat/ clear coat, to keep out moisture. The brush on version i hear is probably better as far as application. ...

 

[1994redram]

I use it. But it sure stinks like hell when you start welding over it.

 

[famous bob]

I use it. But it sure stinks like hell when you start welding over it.

I used it when replacing the floor pans in my 68 fastback, didn`t think much of it , seemed worthless to me.