Rust repair

[Hosedragger622]

Once the area is cleaned, what are you guys using (weld through primer, por 15, etc) to protect the metal from rust before replacing your rocker panels and other patch panels ?

[bigmac73]

i would treat it with OSPHO before priming and painting or POR

[hugger6933]

I use weld thru primer and I use the 3 M spray can kind I have used brush on and it works great too but it dries out in the can before you can use it all. I go through a lot maybe a can or so every month

[firedemon]

i use weld through primer although i believe primer is porous so its probably not the best but paint of any kind will melt so........

[Peanut74]

I've used both. For the vast majority I used epoxy primer and sand the area behind the plug holes before welding. I also used weld through primer just recently and do like the results and makes welding much easier.

[HO455]

That void space is the drain area for the cowl so it will see water any time the truck is rained on. So to ensure the best protection you need a multi product approach. A rusty metal encapsulation/conversion product like POR-15 for the areas that original rusted metal as far up into the void as you can reach.
The new metal needs a waterproof proof primer (weld thru primer isn't) and ideally a coat of paint.
The fly in the ointment is everyplace you weld will have the paint burned off so recoating after welding is the difficult part. I the past i have drilled 3/4" holes in areas that are out of sight so I can use a flexible wand to spray inside the voids then put a plastic plug in the hole and coat the plug on the outside.

This gentleman from the UK has posted a video showing what I consider to be the most informative video on the subject. Unfortunately not all of the products he talks about are available in the US. But he illustrates the muli product process very well.

https://youtu.be/2ElO4gyV6aY

[Davidf]

I use high temp black paint.

[bigmac73]

POR is not a rust converter,it is just a half ass sealer. If you do not convert the existing rust you have including up in the panel that you can not see it will come back,
I do not care how many coats of primer or paint your spray on top of it , get a garden bug spray and fill it with a rust convert like OSPHO and douche it up as far as you can spray and let it soak for 24 hours, then go back and scrub clean and prime and paint over

[Davidf]

The phosphoric acid (OSPHO) will not do much to rust scale. So, yes I agree wire brush and treat what you can see and spray what you cannot and hope for the best. Media blasting is the best.

But, I also believe that you can stop unconverted rust. If you shut off the oxygen supply, the rust will stop. POR 15 is intended to do just that.

[Hosedragger622]

Thank you for all the responses.

[May70]

Ive got a frame that's been under cover or in a garage for 2 years. It was sandblasted, por15'd, primed and painted with rustoleum and its already got surface rust in some spots.

Ill never use por15 after seeing this.

2k sealer and quality topcoat paint.

[Davidf]

Originally Posted by May70

Ive got a frame that's been under cover or in a garage for 2 years. It was sandblasted, por15'd, primed and painted with rustoleum and its already got surface rust in some spots.

Ill never use por15 after seeing this.

2k sealer and quality topcoat paint.

Hmmm...I have media blasted parts covered with Rustoleum paint on restored cars that are now approaching 10 years old with no rust showing through. No primer, so sealer, just rustoleum. Must be the prep or not using enough material.