new to welding...

[mitchcj1]

So I am replacing shock towers. I ground the points of contact btwn the tower and apron. My question is what kind of primer or paint can you use so it wont rust in between. My welder helper guy said primer would just melt off when you welded. Leave it bare metal and seam sealer after? Heres a picture to help visualize. Beware, it isnt pretty...

 

[HHStang]

you can prime and paint after you weld. Be sure to grind or blast your weld slag off before painting though.

 

[Platonic Solid]

Weldable Primer

3M Weld-Thru Coating 05913
.

 

[68rustang]

I have used weld thru in primer in the past. The 3M stuff is the best of what is out there, but that isn't saying much, all of it sucks. IMHO you would be better off welding to bare steel and then seam sealing and painting.

 

[tos]

I use a weld thru spray primer by seymore. It works very well. Bare metal does weld better but if you want the best protection over the long run i'd prime it first. even the auto industry pretreats there body panels before assembly. What I would do in your case is drill or punch 1/4 inch holes every couple inches in your replacement piece and mount it in place with several self drilling/tapping screws then take a scribe and just scratch alittle of the primer off at each welding point. this just makes starting the arc a little easier however its not all that necessary. This is called rosette welding and it works real well. remove your screws and weld those holes up. Grind the welds smooth after words and you'll have a professional looking and strong repair.

 

[68rustang]

...even the auto industry pretreats their body panels before assembly...

Most unibodies are fully assembled and then dipped in a large "ecoat" tank. In this tank an electric charge draws the coating onto the metal.

 

[slepe67]

On this topic, who sells a pneumatic hole punch? (I'm getting ready to put in floor pans) and who makes a top brand of Seam Sealer? 3M? Thanks

 

[68rustang]

Anywhere that sells air tools should have a hole punch. If you want a one time use tool look at www.harborfreight.com you could just use a drill.

I used 3M seam sealer.

 

[mitchcj1]

good gouge. Thanks guys, I might do primer AND seam sealer just to be safe. 3m sealer ok for the inside of the engine bay? Heat and all...

 

[tos]

Most unibodies are fully assembled and then dipped in a large "ecoat" tank. In this tank an electric charge draws the coating onto the metal.

You are right after assembly they do (or did back when) get dipped first in a cleaning dip and then the coating you are talking about. The process i'm talking about is a pretreatment of the metal which has an oily film look and is a corrosion preventative. Otherwise this stel would start rusting before they even stamped it out. Its a matter of preference really. If your just building a hot rod to play with and the car isnt worth full restoration then you might not care to pre-prime. If your going for show quality or longevity then id pre-prime it. Use the seam sealer too. I prefer the brush on stuff personally. take your time, do a good job, itll be worth it.