Best paint for painting over rust

[Tinker]

Ospho marine and paint. Ospho is basically Phosphoric acid. It'll convert and etch too. Is it better if you can't blast, maybe. POR is fine, just de-grease the area and maybe use some Ospho before too.



POR 15 is designed to cut off air to the rusted area. I used it once on the frame, on the parts I didn't de-grease it peeled off in sheets.


Certainly there are better ways.

[Tim Ayers]

Originally Posted by Kube

Paint over rust? WHAT?

Yes. Original paint '28 roadster. Want to protect the underside while the body is off the frame.

[tubman]

Originally Posted by Kube

Paint over rust? WHAT?

If you are referring to PaintOverRust-15, that's really just a clever slogan they use. It is an Isocyanate coating that has something in it that will chemically combine with iron oxide (rust). Actually, you have to be pretty thorough in getting all loose rust of of the surface, but as we all know, that is pretty hard to do, as what's left after our best efforts is really in there. The chemical property mentioned above actually binds the coating to the rust left on ferrous metal. POR-15 actually works better on steel with residual rust than to clean steel. I have used it and it really works.

You just have to be careful and get ALL of the loose rust (and other contaminants) off and protect it from exposure to ultraviolet rays, either by keeping it in unexposed areas or over coating it, preferably with the product they make especially for that purpose.

[rotorwrench]

No offence Kube but not everyone restores things like you do. I still have a few crusty spots on my Ford 850 tractor engine cowling that I treated some time ago with Ospho and finished over with zinc chromate primer and rattle can Ford tractor enamel and it's still holding up fine. I still use the old tractor pretty hard pulling a brush cutter so I didn't want to spend a lot of refinishing it. Maybe someday I'll "restore" it but like me, it ain't retired yet.

POR-15 works well on surfaces that are not accessible to grit blast or common corrosion removal methods. If it can be brushed or sloshed in some of these weird places then it will encapsulate the corrosion. It's still a good idea to do a phosphate treatment though At least there won't be bare iron oxides lurking anywhere. The iron phosphate is pretty resilient to oxidation as long as it is finished over. It isn't a perfect solution but it is an alternative of sorts.

[deuce5wndw]

I have a 36 I bought that had been sandblasted and rusted. I just got some Rust Blast from KBS coatings and it works really good. The first photo shows where I just dribbled some on to test and this is what it looked like overnight. KBS also makes some outstanding engine enamel that flows out nice with a brush. Just my experience, Dale.

[Mart]

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I wouldn't put any paint on a rusty surface. I would brush off any loose flakes and clean it up without going mad at it. I would then apply some Waxoyl (UK product) to protect it from further rusting. I watch Youtuber Mustie1 and he lives in new England where rust is a big problem. He thins down bar and chain (chainsaw) oil and sprays it underneath his vehicles. It does a good job of protecting from further rusting. It needs to be reapplied after a couple of years or so but if I couldn't get waxoyl I'd use that. His latest video on engine problems on his toyota truck shows him reapplying the coating.
Mart.

[Bluedot]

There is a Loctite product called Extend that I have used for years. It's another rust convertor, turns it black, works great. Only drawbacks: it stinks, it'll stain your fingers, and takes 24 hrs to cure before any topcoat. But the end result has always been good for me.