Underbody Finish Suggestions

[millerguy76]

I'm looking for some ideas on how to finish the undercarriage/underbody of my J10. I'm talking about the bottom side of the floorpan. This doesn't include the frame. That is powder coated and removed from the truck right now.
So I'm laying on my back and starting to remove the rubber coating that was applied by the factory. I'm doing my best but don't think I'll be able to remove every bit of it. There are too many nooks and crannies that I can't get into.

So getting to my question, Any ideas how to refinish the underside of my cab + truck bed + fender wells??? I do not want to use a rubberized coating. Whatever I lay down, direct to the surface has to be able to adhere to bare metal, painted metal and in some spots, the residual OE coating. It also has to be paintable as I'd like to lay a smooth satin black over it.

Thanks

[sierrablue]

POR-15 is what I've used for that, either spray-on or roll-on, but I think that's technically rubberized. I think most of the stuff that's going to stick like that will be. I've had good luck with the POR so far, and it's self-leveling and gives a nice show finish, but that's just what I've had good luck with. It's not the most budget-friendly option either.

[millerguy76]

POR-15 is what I've used for that, either spray-on or roll-on, but I think that's technically rubberized. I think most of the stuff that's going to stick like that will be. I've had good luck with the POR so far, and it's self-leveling and gives a nice show finish, but that's just what I've had good luck with. It's not the most budget-friendly option either.

Thanks for the feedback. I've been looking at Eastwood and POR.
I contacted Eastwood and they suggested rust converter and then paint over with Chassis Black. I was skeptical because there is not really any rust. (I'm literally dealing with a rust-free body). So why add rust converter under a chassis black paint? And at very least, wouldn't I need an epoxy primer?
I looked at the POR as well just wasn't sure how it would set on the areas that I can't clean the old surface out.

IMG_20230812_201259.jpg

[sierrablue]

Seems to do ok on those surfaces, might need 2 coats but other than that not an issue I've had.

Those floors are gorgeous btw. And with no scratches or anything there I wouldn't do anything other than put the carpet back in on the top, unless there's going to be a lot of in and out with wet/salty boots, etc.

Like I said, I've had good luck with the POR. I know other guys like other stuff too. Whatever you get, watch yourself, as the fumes are toxic on all of them.

[tgreese]

POR-15 is a moisture cured urethane. It famously has little resistance to sunlight, but you would paint over it. MCU is often used as a paint-over-rust product, a rust "encapsulator." The resin scavenges moisture as it cures, and this will stop surface rust from continuing to rust. A rust "convertor" is a chemical (ie Naval Jelly is phosphoric acid) that "converts" the rust by reducing its oxidation state via chemical reaction, ie from red iron (III) oxide to black iron (II) phosphate. This stops the rust spallation but the surface still needs to be top coated.

There are plenty of other MCUs available. I like Aluthane. It's a quality resin and contains lots of aluminum pigment. https://www.epoxyproducts.com/aluthane.html

If your surface is all bright steel, why not use epoxy primer and paint over that? SPU makes an excellent epoxy primer that I have used. https://www.southernpolyurethanes.com/epoxy-primer Epoxy dries hard, so hard that you should top coat within days or the paint won't stick.

You could cover with bed liner too. Project Farm has a nice series comparing bed liner products. https://www.youtube.com/watch?v=e8RY-Z0ObgY Kinda think that's the only type of product that's going to fill in around the old rubberized coating and stay put.

[millerguy76]

Thank you for more info.
The issue is more that the bottom of the cab wont be 100% cleaned. There isnt ant rust issues. Ive read where some of these encapsulators or rust preventers adhere to rusted surfaces. Mine is a bit different in that rust isnt the primary issue. The bigger concern for me is that whatever i use, it has to be able to bond to bare metal, old rubberized coating (where i cant get to it) and some painted area (some areas where i removed the rubber coating, but left the OE paint to prevent flash rust)

[tgreese]

There should be no problem painting over old paint if it's still bonded to the steel. You may want to scuff the surface of the paint with some sandpaper or a Scotch Brite pad before painting, and wipe it down with a wax and grease remover. Again, SPU has a wax and grease remover that I have used and it works well. The surface must be clean of grease and oil before you paint, regardless of what product you use. Any caked on grease or dirt I'd remove as much as possible with a pressure washer first, and maybe get in there with a stiff brush and Simple Green or Purple Power or such.

Kinda think you have no perfect solution for the unreachable undercoating. I suspect anything that's well hidden will still be in good condition, and won't be coming off anytime soon. I'd just paint over it and call it good. You can apply with a brush or roller, since it's going to be out of view. Epoxy or MCU both go on good that way.

[millerguy76]

Thanks. Thank you both for the help.
Next to the realization of the expenses associated with this project, this is by far, the worst part.