Removing rust from frame

[macdude443]

I'm thinking of trying a chemical to remove rust from the general underside/frame.  I hear great things about Klean Strip "Phosphoric Prep & Etch", available at Home Depot.  It's roughly $15/gallon.  From what I read, you apply it and keep the area as wet with the liquid as possible.  Then wait 24 hours.  The rust turns to a black, sometimes scaly finish that you can rinse off.  Underneath is bare metal.  I will then use an etching primer, followed by some sort of enamel.

Has anyone used this stuff?  Does this sound alright?  I would like to do POR-15 down the road, but I want to at least halt the rust until I'm ready to do it.

[Canoe]

Check how bad the rust is.
Does it really have to be removed or can it be sealed so it can't rust anymore?

Consider: remove scale, brush on Penetrol, dry, undercoating (Waxoyl).
If you really want to remove the rust first, use Evapo-rust. It works (and not an acid). It's expensive, but you save tons with the Penetrol being under $10 a can.
You can paint over top of the Penetrol if you want the frame a colour, but if you want to protect from rust, use Waxoyl.
search the nest for Penetrol and Waxoyl

POR-15 is expensive.
I've used POR-15 with their degreaser as per their directions many times. It has failed in every application on steel (clean, rusted or de-rusted) that I have used in service (peels & rusts, or rusts through).
It did work well when mixed with polyester spheres into a slightly dry slurry and used as a body filler (colour didn't yellow either), but that's a very expensive body filler.

[macdude443]

Hmm, well I already have the Penetrol.  I just heard very good things about the Klean Strip product for the price.  Either way, if I get the rust spots down to bare metal, do I then apply the Penetrol and let it dry, followed by the Waxoyl?  How long can I wait in between the Penetrol drying and the coat of Waxoyl?

[Canoe]

Hmm, well I already have the Penetrol.  I just heard very good things about the Klean Strip product for the price.  Either way, if I get the rust spots down to bare metal, do I then apply the Penetrol and let it dry, followed by the Waxoyl?  How long can I wait in between the Penetrol drying and the coat of Waxoyl?

I don't know what you have to do after "Klean Strip". As in, what residue does Klean Strip leave that may prevent something applied to not bond or cure.
With Evapo-Rust, it's a water rinse, dry.

After Penetrol, I wait a week. It doesn't "dry", it "cures":

• dries as the solvent flashes off, then
• polymerizes
• unpolymerized ends oxidize

The surface can feel dry, but within the layer it hasn't finished curing (press and you'll see).
 

[macdude443]

Ok.  Klean Strip leaves a scaly, black residue that you rinse off to find bare metal.  After which I would prime, paint, penetrol and waxoyl.

[Canoe]

NO!

Penetrol on bare metal or rusted (scale removed), then a top coat of paint if you want colour (but you're covering it with black Waxoyl...), then Waxoyl.

I'm concerned about what is left behind by the Klean Strip after you remove the scaly black residue. Like the difference between truly degreasing something vs. spreading the grease around. There may be trace chemical residue.

[macdude443]

Good thing I asked.