Epoxy and rust converters

[Cuda416]

I'm approaching the point in my project at which I'll need to get the bar metal sealed with epoxy and in researching various rust converters I ran across a couple of videos where ospho was applied in different ways and then sprayed with epoxy. Predictably the best results were when it was applied, allowed to dry, then wet again and washed off to neutralize it. Any other variation resulted in the epoxy bond failing.

These tests were done almost 8 years ago I think and the guy followed up 7 years after the tests by bringing out the test panels to do some more testing as a point of curiosity. When he cut the panel into small test pieces, the epoxy peeled off in sheets.

I can't say for sure the panel was the correct one, but the original test included applying filler on top of the epoxy and hitting it with an air chisel. The reuslts were damn impressive when things were done "right" as zero epoxy was able to be removed.

The question then is simply does the epoxy bond break down over time? I find that hard to believe but man, having the paint on my car peel off years down the road would sure drive me nutz.

I'm curious about any and all methods of metal prep folks here use and what epoxy is going to results in the most durable bond.

EDIT: Part of what I'm seeing are comments from the folks at SPI who are really against the use of ospho etc.

 

[Juan Veldez]

If you are talking about under-body, suspension components, or other areas "covered up", I would suggest you look into Por15. They have a few colors to choose from. Just remove dirt and grease. It works best when you just paint right over the rust. If you are talking about the actual exposed body panels, disregard.

 

[Cuda416]

If you are talking about under-body, suspension components, or other areas "covered up", I would suggest you look into Por15. They have a few colors to choose from. Just remove dirt and grease. It works best when you just paint right over the rust. If you are talking about the actual exposed body panels, disregard.

Not suspension etc, rather I'm talking about inner structure areas etc. Rust on suspension parts is easy, reoccurring rust behind a quarter panel is terrifying. lol. I know some people use POR-15 in those areas as well but like everything else, there is always someone who will complain about POR-15 as well. I've also seen reference to people using rustoleum in these areas, sometimes with the hardener.

I'm also aware of a lot of the epoxies have corrosion inhibitors in them as well so for a "clean" panel I'm fine with the typical answer of mechanically strip, then wipe it down, clean and spray (oversimplifying I know).

Ultimately I'm concerned about the possibility of the epoxy peeling down the road if that's actually a real thing.

Thanks for your input, it's much appreciated.

 

[340sport]

Epoxy applied properly will not peel. It should be top coated though. If you are thinking about going the POR route, consider Rust Bullet. In my opinion, it's a superior product.

 

[Juan Veldez]

Not suspension etc, rather I'm talking about inner structure areas etc. Rust on suspension parts is easy, reoccurring rust behind a quarter panel is terrifying. lol. I know some people use POR-15 in those areas as well but like everything else, there is always someone who will complain about POR-15 as well. I've also seen reference to people using rustoleum in these areas, sometimes with the hardener.

I'm also aware of a lot of the epoxies have corrosion inhibitors in them as well so for a "clean" panel I'm fine with the typical answer of mechanically strip, then wipe it down, clean and spray (oversimplifying I know).

Ultimately I'm concerned about the possibility of the epoxy peeling down the road if that's actually a real thing.

Thanks for your input, it's much appreciated.

I did the entire interior of the car with Por15 and the underside of the body (with black). There will be zero rust for the next 50 plus years. But trying to over paint this stuff is really tough, but for me, unnecessary.

 

[Adam]

I use ospho a lot. The directions say to rinse it off, which I don’t do because I get flash rust. Instead, after a normal application, I wipe it down with water that has a little ospho mixed in; I don’t let it dry on the surface because it leaves a sticky residue. On an exterior panel I generally wipe it down with wax & grease remover, then spray the primer. On inner structures and other pieces I use an etching primer on the bare metal followed by a urethane primer. I’ve never had a primer failure. Even epoxy should be top coated relatively soon because 1. Your application may be porous and 2. You won’t have to scuff, clean, or sand the epoxy for the sandable primer coat. It saves you some work in the long run.

I’ve read that por-15 has adhesion problems on clean, unrusted, metal; and it doesn’t hold up to UV rays long term.

 

[heminut]

I’ve read that por-15 has adhesion problems on clean, unrusted, metal; and it doesn’t hold up to UV rays long term.

When I was replacing all the rusted sheetmetal in my Cuda over 20 years ago I replaced the dutchman panel with a new one. Since the bottom channel where the back glass goes was notorious for rusting out I coated it with POR 15. New metal, no rust and it is still holding up great. I also did a new steel battery tray (a race car part) with POR 15 and when I got rid of it about 10 years later the POR 15 was still holding up fine.

 

[PLUM_72]

Sandblast then epoxy is best. If you're not sandblasting, go over the area with cup brush on a grinder, then I like to apply Rust Bullet. This stuff IMO is better than POR15. It is silver in color, can go over rust, baremetal and painted surfaces and bonds very well. It can be sprayed or brushed on depending on the circumstances. Being silver in color you typically need to top coat it with something. OSPHO, I leave that stuff for inside frame cavities or areas where you dont have direct access. That stuff can be sprayed in with a trigger bottle sprayer and the excess allowed to trickle out.

 

[340sport]

You can use Rust Bullet Automotive Formula as a stand-alone coating, or in combination with Rust Bullet BlackShell, WhiteShell, DuraGrade Color or Clear Shot for rust protection. Rust Bullet Automotive is metallic gray in color and can be brushed, rolled or sprayed.