I don't mean to beat a dead horse here, but I'm guilty of falling into deep void that every minor van build detail leads to if you poke around enough!
There are hundreds of anecdotes on various forums (including this one) about POR15, and much of it is praise. I have seen in general that the forums with higher concentrations of auto body guys have a less popular opinion of POR15.
I was about to pull the trigger on some POR15 in order to coat and seal the floor of my van as the first step of my van conversion before the insulation and subfloor go in. A few exceptional van builds on this forum made use of it for sealing the van tub. But, I just haven't been able to go through with purchasing it, because every bit of logic seems to indicate that this is the wrong product to use. Let me explain why:
1) It's a rust encapsulator. My van floor is 98% rust free. It can be applied to roughened, clean metal, but why? It's a rust encapsulator. It's meant to be Painted Over Rust. It's a moisture cured urethane that can be painted over the surface of rust and draw out the moisture in the rust in its curing process and create a starved environment and great seal. However, this seems heavily dependent on near perfect prep and atmospheric conditions. As a side note, there are a lot of guys on the auto body/restoration type forums that regard any rust encapsulator as, ultimately, the result of a "that'll do" attitude of the hobbyist or money-strapped enthusiast who refuses to do the job correctly by simply eliminating the the rust in the first place.
2) POR15 cures into a very hard and rigid material. Yes, it's very durable, but also has very little flex. Will this present problems as the body of my van flexes offroad? What about the dissimilar expansion and contraction rates of the POR15 and the underlying metal? The last thing I want is for cracks to form in the POR15, creating perfect little rust hotels.
3) It's more expensive than epoxies or enamels that seem to be better suited for metals that are properly prepped and rust free.
I don't doubt that people have gotten good results with it on clean metal, especially a van floor that will be hidden from exposure, but I'm trying to figure out why it would be the first choice.
What's the alternative? Well, my thinking is to hit any spots of surface rust that are in seams or hard to reach places that I absolutely cannot grind out with a rust converter like Ospho or SEM Rust Mort. Will any such places actually exist? I don't know. And then paint it with an epoxy or enamel. I haven't been able to find a single bad thing said about SEM Rust-Shield, an enamel, and it does not require the etching acid that POR15 does for clean metal. On the other hand, epoxy is cheap, durable, and flexible.
Please excuse the rabbit hole induced rant
Am I missing something here?
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