Best coating/paint/rust protection for underside of floor and floor pans

I haven’t had to do that, luckily my car is rust free. I live in the sw though. Based off reading other members threads and what they used, POR15 is probably want you would want to use again. If I had to, that what I would use. Why is it so labor intensive?

Blucifer99 said:

hey im looking for aadviceon the best paint or rust protection or both for the underside of my mustang... I have little to no rust under my car.. Basically planning on sanding the whole underside and re priming and painting.. I have considered por15 but the prep is crazy thats needed.. Looking for suggestions on what type kind to use.. Any input is good input. Also i have already por15 my whole inside floor pans. And thats why im lookin for something alittle bit less labour intesive. Cause that was a total pain.. Sanded to bare metal the whole inside pans and then basically days of cleaning resanding then etching and it wasnt fun..

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I thought that POR15 could basically be painted right over the rust? I have an ‘02 F150 that I’ve decided to keep til it won’t be kept anymore, and was thinking of doing the frame in the POR stuff. I may rethink if it’s that much work. I do hear it’s the best though.

I know what you mean on the POR-15... it's does not like clean un-rusted metal, you have to use there metal ready, which is just an acid... and keep it wet with that stuff for like 15min, then wash off... if you don't, that stuff will peel off..... which sucks, last thing I want to do is put water on it...

I just bought this stuff a month or so ago from Eastwood, it's there new Rust Encapulator called Platinum... you don't need that kind of prep...

here's a link to it - https://www.eastwood.com/eastwood-rust-encapsulator-platinum.html I'm hoping it's as good, as the por-15, I do know, if you get some on you, it's hard as hell, just like the por-15 to get off.... ask me how I know...

I also used there internal frame coating... to spray inside all the frame rails, front and rear, going to do inside the rockers too this spring when the weather warms up.... which i used/treated it alot more then needed.. and will maybe re-do every once in awhile... to make sure... after fixing the strut tower areas on mine, I don't need to do that again...

fyi, I did notice when I was putting my re-main rack in, right before I put motor back in, I found some light rusting spot on my k-member... now a year or 2 ago, while out of car, I sand blasted it, and used the por metal prep and kept it wet with it for 15+ min... put 2 coats of por-15 on.... so I don't know why I got those couple areas of rust... I wasn't happy about it... I went over those spots with the eastwood platinum and top coated with black paint... so I hope it keeps it at bay..

Here’s one of several tech sheets about POR 15. It can be used on top of a painted surface.
https://www.por15.com/POR-15-FAQS_ep_61.html
It is different than most paints in its bonding ability to a rusted surface.

Yet when coating a painted surface it will need to have the substrate abraded to help in the mechanical bonding to the surface. Just as any other paint or protective coating would need too.

Clean smooth metal will still need an etch for it to bond properly.

Don’t worry about rinsing off the phosphate coating when doing the etch prior to coating with POR 15. The metal will have a protective coating created by the phosphate wash. You aren’t rinsing bare metal at that stage.

Use Eastwood platinum. Just recently applied it to my truck frame with a good amount of rust and I was impressed with the results. You do have to sand down the areas with heavier rust but not down to bear metal. If the underbody has hardly no rust then all you gotta do is whip area with acetone and paint