Lap-joint welds and corrosion prevention

[Gusb]

With all the spot welded lap joints everywhere on a 40, what's the proper way to prep and finish the weld area. For example when one piece of steel goes over another and gets a welded, is some kind of weldable primer usually the only protection that the enclosed area ends up with? How would you protect that hidden area from future corrosion? I would think the seam would get sealed (like factory) after/before painting but how clean/protected is that hidden weld? Anyone ever hear of silver-soldering, etc. (sort of like an old high-end bicycle joint) a lap joint after welding and before paint to seal the area, etc. Or would that create it's own issues with acid flux, etc.?

Thanks -

 

[WarDamnEagle]

You can buy weld through primer. This U-Pol stuff is supposed to be the best:

U-Pol Weld-Through Primer (Aerosol Can)

 

[davegonz]

Wow! That stuff ain't cheap.

 

[Toyo FJ40]

I brushed seams after welding with por 15 to seal the seam. Weld through primers are good when you can't get to the back of the area after welding like rocker panels.

 

[Gusb]

I brushed seams after welding with por 15 to seal the seam. Weld through primers are good when you can't get to the back of the area after welding like rocker panels.

That's a good idea - I know from experience POR will really "leach-in" to cracks, etc.

So I guess use a good weld primer, hit the seam with POR15, a good paintable seam sealer on top of the dry POR and then final paint? I'm guessing the POR will not react with the weld primer in any negative way?

 

[WarDamnEagle]

I think the POR15 will stick to the weld through primer but you might want to use some of their metal ready just to make sure.

I would be concerned about anything sticking to the POR15 after it has cured. You might need to spray some of their self-etching primer on it before you use the seam sealer. POR15 is pretty slick stuff once it's cured.

 

[Toyo FJ40]

You'll need to scuff up the Por15. I used a 3M pad and haven't had any issues. Por15 says it won't react to automotive paints.


Kevin

 

[Project60]

I bought weld thru primer at my local Finish Masters (auto paint suppliers). The in house brand is $9 for a 15oz aerosol. The SEM brand is like $12 for a 15oz aerosol.

It works good. It doesn't catch on fire, burn or smoke like an epoxy primer did for me.

I am not sure if the weld thru primer is moisture resistant... so best to topcoat like suggested.