welding prep ?

[bigdave R.I.P.]

I'm going to install a new trunk floor and need to know if I need to remove the DEP coating on both sides of the new metal before welding.
thanks

[Rick_L]

You need to sand it off where the welds are.

[bigdave R.I.P.]

I read and used weld through primer before. Is that what I should prep with or is bare metal better. I'm just worried about rust like everybody else.

[NickP]

Dave as Rick indicated, remove from an area you will weld. What is your process? If you are spot welding with a spot welder, all four sides need to be bare metal for the process to work. If your original metal has the holes from the spot weld cutter, then the mating surface at the location of the weld should be bare metal. The DEP will cause issues. On the floors I did, just did the whole mating surface. In the areas I used my spotwelder I used a 60 grit 3" pad on all four sides.

As to future rust, a good sealing primer after welding will eliminate the surface you can see rusting for a long time. As to the mating surfaces sandwiched in there, or the area burnt away after welding over weld through primer, clean it and spray some more on the afected area. A seam sealer wil for the most part protect, but getting inbetween is impossible unless you could dip the body and even then, your not going to get it all.

[bigdave R.I.P.]

I'm usimng a spot weld cutter to remove the old floor and will sandblast the area where the new metal will meet. I'm going to plug weld the new piece in. I will clean up all the metal that wil be sandwiched and the area around the holes.
thanks.

[Chevynut]

I would remove all of the EDP if you can, and spray the whole floor with a good epoxy primer. No telling what kind of stuff they used on it, and it could compromise your future finish.

[jeffs55]

I concur and will add, be careful blasting the sheet metal and don't warp it.

[Rick_L]

You aren't going to warp a floor by sandblasting.

[AlwaysWantedA55]

When installing my new floor, I used copper-based weld-thru primer on the mating surfaces after sanding the metal bare, then plug welded everything together. I will also seam seal, and intend to remove all EDP and shoot every surface in epoxy.

[bigdave R.I.P.]

Thanks Guys. I'll plan on removing the EDP coating.

[MP&C]

I use a modified drill bit, same size as the plug weld holes, to clean the paint off the adjoining panel inside the plug weld hole. The modified bit is formed using a 3" sanding disc, flattening the end, and then back facing to mimmick and end mill cutter. Once your panels are clamped together (with plug weld holes predrilled) a few revolutions with this bit inside the plug weld holes, will clean off the paint from the adjacent metal and give you nice clean surface for welding.


http://i5.photobucket.com/albums/y167/rmccartney/Misc/146d4d8e.jpg

http://i5.photobucket.com/albums/y167/rmccartney/Misc/90c0a095.jpg

[bigdave R.I.P.]

Thanks for the tip Robert. I found a bit from DeWalt that looks alot like that. it has a center tip from starting the hole.

[MP&C]

With this one being flat, it doesn't harm the adjacent panel, just removes paint...