The Stovebolt Site Forums The Shop Area Paint and Body Shop Welding fender patch question

Folks, I'm about to weld a patch onto my fender.
How do I go about treating the metal that is not welded?
I figure that moisture will get between the sheets and start rusting from the inside out.
Here are a few pictures. MyBlog

Thanks for the help.

-Pete

Not much you can do. I typically paint the backside (side hidden once both pieces are welded together) with high temp paint. The welding process will still burn off the high temp paint immediately around the welds. If possible, the seams get seam sealer to keep out moisture.

If the repair is simply a patch, I avoid lap welding and use the butt weld method. But, I believe you are talking about two pieces lapped together and spot welded.

you are right, rust will form between lapped panels just as in the original factory pinch welds, the best thing you can do is avoid lapping patches as David says, or use the high-zinc weld-thru primer on the pieces before joining - but be aware the fumes are unfriendly

Bill

High-zinc primer... I'll look for it. Glad I asked the question, always something new to learn.

I have a follow up question.
I was planning to run a bead along the edges then cut off the excess. I think some folks have indicated it might be better to drill holes then fill the holes. Sort of like a spot weld.
What are your opinions on the best method to weld this up.

Thanks again

on lap joints, try to mimic the factory spot welds via the plug welding method (I use 1/4" holes). Only do lap joints if the factory did lap joints. Center the hole in the lap. Don't weld the edge of the lap (use seam sealer to keep water out).

Cold galvanizing spray or weld through primer is what to look for.

Not cheap but this is what I use. Clean (no residue solvent) and spray all interior parts. Wait time on instructions, well ventilate area and weld.
http://www.eastwood.com/eastwood-s-self-etching-weld-thru-primer.html
Mike

IMHO, weld through primers still burn off around the weld. Not much you can do about it. I use regular high temp paint and simply use my dremel tool to clean the paint from the area to receive the puddle weld (after parts are assembled, clamped and ready to weld).