How much to remove surface rust before por15

[dm]

So if my pans or another part of the body just has surface rust, how much should i work to remove before adding phosphoric acid and the por15 or other treatment? Do i labor for hours and try to sand and remove all tiny rust spots or just sand what essentially what i can then add the phosphoric acid and then por 15 it?
Also, my understanding is por15 is not very good if you are going to paint the metal. If so, whats the best thing to use if i want to paint?
Thanks!

[catahoula lou]

Just went through this with my 59 ragtop.

I would wire-brush the heavy rust and then spray with the phosphoric acid, keeping it wet for at least 30 minutes or so. Rinse off with fresh water, towel dry, then spray with acetone to carry away remaining water. Repeat, as needed.

Let dry overnight, then put on POR-15. I used the glossy black POR-15, as it's much easier to work with.

If you're spraying the acid anywhere that it can drift onto paint, tape/cover it, as it will slightly bleach the paint (protects against acetone overspray/drift as well).

I did two coats of POR-15 and looks good 1.75 years later. Transfer POR-15 into a mason jar before you begin, as the can/lid is not really designed for multiple openings/closings and will let the contents dry out after you've bent them up...

Best,
Thom
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[NOVA Airhead]

[kiwighia68]

[Mellow Yellow 74]

My experience with POR15 is that it needs a slightly oxidised surface to adhere to the metal. Someone - I think it was Dorian from Belgium - suggested wetting the surface to be treated and letting it react to the oxygen in the air before applying the POR15.

Where I used a rust converter, the POR15 didn't adhere well and in places flaked off.[/quote]

Not sure about this - the POR15 metal ready preparation product removes surface oxidation
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1985 Caravelle (Vanagon)

[dm]

Thanks for the responses. I pretty much wire brushed and added phosphic acid, then the por 15 the next day for the pans.

I was asking about how to treat rust for metal that will be repainted? Unfortunately, welding isnt an option for me at this point so I do want to do as good a job as possible when there is surface rust and some pitting.

Thanks!

[Starbucket]

If your pans are thin from rust and you are treating them inside the car, laying some thin fiberglass cloth over the 1st coat of por15 and follow with two more coats of por15 will add a lot of strength and keep you from falling through while driving.

[Starbucket]

[dm]

Ok thanks! Is that just like phosphoric acid or different?

[Starbucket]

It's different. It's what paint shops put on bare metal before primer.

[dm]

Great! Thanks!

[c21darrel]

POR's metal prep may be different, but not much. Seems it does all the same things Phosphoric acid does at only twice the price.
http://www.homedepot.com/p/Klean-Strip-1-gal-Phosphoric-Prep-and-Etch-GKPA30220/100406369

Pretty much does the same thing. Now, if you are using POR you may want to use all their products as a system. Im just not a fan of that product.
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