POR15 vs. EPOXY PRIMER for underbody rust (quick but permanent)?

[epowell]

In the image below - this is the kind of rust I need to deal with in my "B.C. van" Antonio. Part of the problem is that there is a lot of deep surface rust and I don't have unlimited time to deal with this... normally what I would do would be to grind off all the rust, hit with rust converter, then EPOXY PRIMER.

But since I have a bit of a time limit in Vancouver, I am considering using POR15 instead. I heard that some folks have had good results without grinding off any rust at all - rather just cleaning and de-greasing the rusted areas before applying POR15.

I think what I would do would be a kind of middle-way... grind quickly as much as possible off without trying to be perfectionistic - then de-grease - then POR15.

I would like to hear some advice of this before deciding. It's not like I do not have the time to do it "properly" (grind off all rust, then epoxy primer), but I have only 4 weeks in Vancouver and always need/want to do other things also.

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www.edwardpowell.com

[jlrftype7]

I would not use the POR15. Wire brush the worst, then spray rust converter from a plastic spray bottle for faster coverage versus brushing it on.
Then spray Zinc Primer, also known as cold galvanizing paint on , once the converter dries. It’s reversible when you work on this later on ,and will possibly cling better to the body.
Not expensive either, as you probably only need a can or two of both products.

As an example

https://www.homedepot.com/p/Rust-Oleum-Professiona.../100142963
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'68 Westy- my first VW and vehicle/Bus- long gone.- sold it to a traveling Swiss couple....
'67 Type 3 Fastback, my 2nd car- gone
'69 Semi-Auto Stick Shift Beetle-gone
2017 MINI Coopers, our current DDs
‘84 Tin Top - Hilga....Auto

[tjet]

[RalphWiggam]

Get some MasterSeries silver primer. Ive used everything and MasterSeries is by far the best.

[jlrftype7]

[ZsZ]

I would wire brush, apply rust converter and spray waxoyl when the converter dries.
Although I don't know if waxoyl is available in Canada or US
https://www.amazon.co.uk/Tetrosyl-Carplan-Waxoyl-Rustproof-Protector/dp/B01FSO42GK
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Zoltan
1.9 MTdi 2wd Multivan (ex Caravelle)
Van since 2006, engine since 2008

[dobryan]

POR-15 works well on a rough rusty surface as a top coat to encapsulate the area under it. It has drawbacks though. It is brittle and can chip off and then water gets under it and creeps along the rusty substrate and continues to rust even though the POR-15 on it looks good.

Wire brush/wheel and Ospho then a primer are the way I'd go. It will not really take any longer.
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Dave O
'87 Westy w/ 2002 Subaru EJ25 and Peloquin TBD

"To travel hopefully is a better thing than to arrive." Robert Louis Stevenson

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[epowell]

Thanks for these replies...

Seems the main problem with POR15 is that it is more or less a "one way ticket". You don't want to be in a position later on to want to remove it.

This predicament opens up a few questions:
1) why would one want to remove it later?
2) what are the chances of the rust coming back after POR15. Seems the answer to this would depend upon how bad the original rust was and how much of it was removed before POR15 was applied.

I would NEVER just apply POR15 without at least getting rid of the majority of the rust first - but my current curiosity about the POR15 option lies in the time saving factor between grinding off ALL the rust vs. about 70% of it. That last 30% can be the most time consuming (and toxic dust - the last thing I want when travelling internationally is to do something that might give me symptoms of respiratory issues).

PS. Missed the last 2 replies. Yeah I hear ya Dave, The last thing I want is having it look great yet be disintegrating from the inside out > I guess if I intended to sell the van soon that would be another story, but I intend to keep Antonio for life. Same with GEorge <3
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www.edwardpowell.com

[4Gears4Tires]

As Dobryan said, you'd have to remove it if it chips and then water seeps underneath.

My suggested method: Wire wheel (or brush, but it'll take much longer) all the loose surface rust, then paint everything in 2 coats of 3M Mar-Hyde.

Rust

Mar-Hyde

After a day of curing, you can coat it with whatever paint you want (even POR15) for additional protection. The benefit of using Mar-Hyde or Ospho is that it catalyzes on the rust forming the protection layer. POR15 is just a paint that seals out the moisture, which is good, but not the best way.
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'87 Syncro
Ferric Oxyhydroxide Superleggera Edition

[epowell]

So what's up with this "OSPHO" stuff? Is this kind of a deluxe rust converter?

So can I assume that the best method is:
1) grind off all the rust including pits
2) treat with OSPHO
3) apply epoxy primer
?
https://www.caswellcanada.ca/OSPH1G.html
_________________
www.edwardpowell.com

[4Gears4Tires]

No, it's just a rust converter. There are many out there.

https://www.carbibles.com/best-rust-converter/
https://chemicalwiki.com/best-rust-converter/

I use Mar-Hyde because several trusted friends independently suggested it. It's also used at D.C. Metro and if its good enough to try to keep up with train maintenance, it'll be good enough for my van. It is, however, quite a bit more expensive than Ospho with Mar-Hyde being $45/quart and Ospho being $30/gallon.
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'87 Syncro
Ferric Oxyhydroxide Superleggera Edition

[epowell]

[Californio]

Anything brittle is eventually going to fail. That's always been the problem with POR15.

If the rust isn't so deep that it's threatening structural integrity, I'd vote for Waxoyl. It keeps the water and salt out and flexes with movement and heat. Maybe a light wire brushing beforehand.

[dobryan]

[epowell]

[dobryan]

[epowell]

So for sure I'll properly do the rust on the frames and the floor underbody...
...but I'm still not completely sure what I'll do with areas like on this foto.
Rear backing plates and trailing arms.
These parts ultimately are replaceable so it might be an option not to worry too much about them, then eventually replace...

...I think for now if I don't have time to grind off the rust (probably won't), I'll just keep spraying them each year with rust converter before storing the van. I suppose I could hit it all with a coat of cheap primer?

_________________
www.edwardpowell.com

[skills@eurocarsplus]

[Vanagon Nut]

[flomulgator]

Never heard of MasterSeries, but I will say I switched from POR-15 to RustBullet and RustBullet seems to be a better product. Doesn't seem to get brittle and has better texture for topcoat. POR-15 I've always felt the need to sand if I was going to spray something on top of it.
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