POR-15 & bondo

I was preparing the inside driver's rear cab corner on my FC-150 for several coats of POR-15 when I found some rusted through holes in the sheet metal so I went after them with a grinder and sander. As always they got bigger before I got to good metal. They are going to have to be filled with some bondo and plastic screening. My question is do I fill the holes first and then apply the POR-15 or apply the POR-15 to seal all the metal and then apply the bondo?
There is so much prep work needed to get ready to apply the POR-15 I don't want to screw it up.

 

I doubt bondo would hold well to POR15. It's too smooth and shiny. And there is little gained by painting bondo with POR15. The better question is how best to prep the bare metal for bondo. And I can't help you there.

 

you could scuff it couldnt you?

 

I'd weld it up as well. I dont' use bondo for much since I got a welder. Just for areas I can weld successfully for what ever reason......

 

Never ever fill holes with bondo, ever. It won't work, just weld in a patch or have someone weld in a patch.

 

x4

TD

 

Really, I filled something like a 100 snap holes in more than 12 years ago, not a single one has ever come loose and I bet you can't find a single one of them after all this time. In fact I have repaired major sections of a car body with Bondo and have never had it fail, ever!!

 

Good idea. The holes are about 2" wide. Why skimp now with all this effort, especially on a vehicle (FC-150) with no replacement body parts located in salty New England.

 

I'd expect your success with filling holes with bondo depends a lot on the climate and how the vehicle is used. Bondo is porous, and if exposed, steel in contact with it will rust. Ideally it should be sealed between solid metal and a non-porous primer and top coat. I recall the main problem with exposed bondo is the rusting surface releases the bondo, and chunks fall off.

If I couldn't weld, I would be more inclined to use fiberglass, or epoxy and glass mat... something where the matrix is more resistant to moisture. Look around - likely there is a product out there for this. Either that or glue a metal patch to the surface and seal the bondoed surface from the air. Something.

 

From my experience most of the repairs cracked after one harsh winter. You can cover pin holes and such with bondo and have good luck but that is like a 2 second welding job. I never use it to cover large holes or lay it on thick to make up for bad metal work because in the northeast it, WILL CRACK.

 

It is about a 2 second job, if you have a welder. I didn't until about 2 1/2 years ago have one. As far as temperature, when I repaired the major body work it was in Florida where the temperature swings in winter can be very drastic, 85* during the day and down to freezing that night.
Bondo is not water proof and should never be laid over bare metal and the Bondo should never be left more than 24 hours without primer or paint on it as it will absorb moisture.
A patch panel is the right way to do it i agree, but you must remember everyone does not have a welder and alot of guys couldn't weld sheetmetal decent if they tried for 10 years. I have seen alot of weld jobs on vehicles that sucked big time alot of Bondo jobs just as bad or worse.
Remember, how good of a job you do always depends on the tools you have and the experience using them.

 

I've always used it over self etching primer. I was told that about 30 years ago when I was in HS by a friend of the family that was a body man, been doing it ever since. I've had good luck doing it that way so thats the way I still do it.

 

If you don't have a welder, this stuff is the best thing since canned beer! http://semproducts.com/Catalog.asp?prod=89 Most new vehicles are assembled with these types of adhesives as the sheetmetal is too thin to weld, and the urethane makes a stronger bond. I'd cut patches to fit (with overlap) and glue them in there. You can use a self-tapping sheet metal screw to hold the pieces if you can't clamp them together. Grind the protruding screw off, POR the metal if you want, fill, prime and paint.

 

The conventional way to apply bondo is over roughened bare metal, but at least some PPG primers claim good filler adhesion https://buyat.ppg.com/refinishProdu...roductID=ebd75e7f-7489-4334-a387-73f8653e2a34

I'd suggest you consult the spec sheets for the product you will use.

 

I hate bondo. I've used West System epoxy and glass mat of various weights and/or carbon fiber on a LOT of projects - mainly boats, which flex a lot - with great success. You can get it at West Marine.

So, I have a ton of holes from 1/4" to 1" in dia all over my Jeep that I want to weld up ... where do you guys get round sheet metal "discs" of those sizes to weld in?

 

So, I have a ton of holes from 1/4" to 1" in dia all over my Jeep that I want to weld up ... where do you guys get round sheet metal "discs" of those sizes to weld in?[/QUOTE]

Find a shop or friend that has a hole punch.just get the sheetmetal and punch out sizes you need.takes about 10 min. and there the right thickness and nice and round.thats what I did.

mike s.