Use of Weld Through Primer

[340challconvert]

Preparing the trunk floor for install
Questions:
Should I scuff the EDP before spraying with either epoxy or weld through primer?
Experience tells me yes. I would think I need to go to bare metal in the weld areas to promote clean welds.

I have heard that epoxy can be used on the panels where welding takes place.
Is weld through primer a must?; some opinions I have read show that epoxy could be used instead.

I know the purpose is to prevent rust between panels after install.

I would coat the frame rails and the floor panels, both with the weld-through or epoxy.

Am I on the right track with this?

Responses welcome and appreciated.

 

[aussiemark]

I usually just scuff a little bit of the EDP off as part of the plug weld hole deburring process. I try and leave as much EDP as possible it doesn't catch fire and start bubbling and burning like most paints do, it will burn off a bit but it just turns to ash where it gets too hot for it to handle which is what weld through primer does as well. I usually go about 1/4 of an inch of bare metal around the edge of each hole on the top and just a tiny bit bigger then the hole on the piece that it's getting welded to (frame rail). Once the first plug weld is done the two pieces will have a good earth connection I find the first weld the hardest but some sheet metal screws will help clamping the two pieces together as well as helping to make sure they are both earthed. If you use the wrong paint it will start burning and be hard to extinguish as well as giving off toxic smoke. It doesn't matter what paint you use it's going to burn back a little from the weld so you'll always have a small amount of bare metal around each plug weld but the weld through primer and EDP will keep that amount to a minimum other paints will burn back further.

 

[DetMatt1]

I agree.

 

[Adam]

I agree and would add that weld thru primer is only needed in a few spots that will see a lot of moisture, and not get topped with seam sealer + paint; for example the gas tank support straps. Generally, I scuff EDP with a maroon scotchbrite pad, apply seam sealer to gaps if present, and topcoat with epoxy primer, after the welding is done.

66 Auto Color: Scotchbrite Grit Equivalency Chart

 

[340challconvert]

Good Info
Thanks to the respondents!

 

[AUSTA]

I found when spot welding the EDP coating interferes with the contact so i removed the EDP
& resprayed with copper coat weld through primer also adds good protection to the metal