Por-15 pre or post welding?

[280z1975]

I have read a little bit up on this in threads involving using Por-15 but have yet to get an answer.

So right now I am about to Por-15 my whole floorpans and interior of my car along with a vast majority of the bottom of the car. One thing I need to do is to weld on new frame rails that are coming in some time next week.

So my question is this? If I Por-15 the interior of my car then weld on the frame rails later in the week will I weaken the Por-15 or will it be fine? Should I wait and then Por-15 everything after the welding? Also, I plan to Por-15 the inside of the frame rails (Bad Dog Parts ones that fit over your existing frame rails) and will this affect the weld or the Por-15 on the inside?

Thanks for the help.

[EScanlon]

Gregg:

The "rule of thumb" that we went by at the body shop I worked at was simply this....All metal work (brazing, welding, bumping, cutting, etc) should be completed before ANY painting is done. This minimizes the hazzle of having to re-do everything you've done to the surrounding/opposite areas.

That said, IF you are good at welding and can effect a good strong weld with a nice bead that does NOT overheat the metal, then you could probably get away with coating the inside of the frame rail supports you will be adding. BUT, and this is a key point, you MUST grind to clean metal wherever you are planning on welding. Additionally, on the opposite side of the metal from where you will be welding you can count on whatever is there to be burned off.

So, check to see where the metal pieces will be coming into contact with each other and leave those areas in bare metal and POR the other areas. Remember that the opposite side of the metal will undoubtedly have whatever is on there burned off, so keep that area paint free as well.

I can understand your concern about unprotected metal, but if you take reasonable precautions after the welding such as caulking, or using seam-sealer then you should be ok.

FWIW

E

[hls30.com]

Enrique is once again dead on!

I will add what I do to stop a neked steel (bare steel in a garage will rust in South Ga.)project from its rusting ways:

1) Wipe down all bare steel with laquer thinner-start with a clean dry surface.

2)After the thinner has dried, wipe down the bare steel again with Metal Ready(or any other acidic metal prep that flash coats with Zinc).

3) Grind and prep the area to be welded.

4) Weld as needed.

5) Wire brush the accessable welded areas-fortunately most of the weld scale will be on the side that took the heat, flux and wire/rod.

6) Wipedown and flood both sides of the areas that were prepped and welded with Metal ready-keeping them wet for atleast 5 minutes-a spray bottle comes in really handy-but use eye protection and floor protection-even weak acid etch concrete.

7) Before topcoating/seam sealing (inside and out) rinse the areas with laquer thinner. If you notice some rust forming before topcoating, retreat the affected area with Metal Ready.

8) top coat!

You can collect the mertal ready that drips from the parts, and let the contaminants settle collect the clean solution it and reuse it.

Will

[Jayru]

Every time i read a thread like this i get very confused. How can you coat the inside of the frame rail with por-15 if they are welded to the floor, efectively sealing them off from getting the Por-15 in there?

[beandip]

escanlon and I have used a simple siphon type of air gun to blow POR into all the rails and void areas of the car , including inside the rear hatch , doors , dogleggs and fresh air channel and many others . Harbor Fright has this little handy gun for about $6.00 . One thing you will find with POR paint is that it covers vary well and penatrates into the spaces between the layers of sheet metal that have been spot welded together at the factory. I have one of these guns still in the package some where , if I can find it I will send you the part number . Gary:cheeky: I just reread the first post you made and I question the adding of a layer of metal over a rusted frame rail in the first place . This seems to me , a band ade approach to a serious problem . The existing rust will continue to grow . ''Out of sight out of mind '' is not a good option , in my view . my $ .05

[280z1975]

Every time i read a thread like this i get very confused. How can you coat the inside of the frame rail with por-15 if they are welded to the floor, efectively sealing them off from getting the Por-15 in there?

In my case I am going to be welding new frame rails on ... and I will be able to coat the insides of these before I weld them on. If I destroy the por-15 on the inside it's not to big of a deal because 98% of it will still be intact ...

[kenz240z]

Another thought... You could use a zinc chromate weld through primer. It is made to be sprayed on the backside of panels, fenders, etc, that aren't going to be topcoated. I've used Ditzler DPE 1538 on other vehicles. It's been awhile, though, and a product like POR-15 is probably better to use, especially if you can't remove all of the rust.

[Jackhammer]

One key additional thing I did before welding was spray the areas in question with a weldable primer that I picked from the auto paint supply.

I then basically followed the procedures described by Escanlon, beandip, and hls30.com.

[Kooduh]

I know this is an old post.  read this and had to join to add my two cents.  you can weld trough cured (3-4 days) POR-15, like a weld-thru primer.  you'll have to recoat to cover your weld, but if you got a good ground, weld away.  keep it cool, as usual, spot welding is best, and you wont burn to much paint away.