Just wanted to share a product that has amazed me.

A little background. I live in Pennsylvania and have owned 3 4runners. It has not been easy to keep the underside clean and free of rust. I bought all of them used, and thoroughly inspected each of them before purchase. My newest 4Runner, a 2006 Sport that I just picked up 3 weeks ago, suffers from surface rust on the undercarriage, just like nearly every other vehicle on the road where I live. I'm a person who loves his vehicles and takes care of them, so I needed to find a solution for the rust.

After days of research, and learning from my past mistakes (undercoating), I settled on this product: Amazon.com: Permatex 81773 Rust Treatment , 16 oz.: Automotive

So far I have most of my rear axle done, and have just started on my gas tank skid plate and rear frame rails. I can tell you this product is awesome. We first used it on my friend's 3rd gen, and painted over it with Rustoleum metal primer and paint. His underside looks new. About 1 bottle is all it takes to convert the entire underside of your vehicle.

All you have to do is simply wire wheel and scrape off loose rust, clean with soapy water, let dry and coat with the Permatex Rust Converter. So far I've used 3-4 coats on my rear axle.

Here are some crappy cell phone pictures that do not do the product justice:

One side of the axle done with 2 coats.


The product goes on white and foamy and dries HARD black as it converts the rust and makes it stable.



More pictures to follow...

When you're done with that blast the entire underside of the truck with Fluid Film (get the gallon & spray gun.) It'll stop rust from starting/spreading in all the nooks and crannies you can't see.

Thanks for the post.

So far, MY favorite product is the Rustoleum Rust Converter/Primer. It goes on a dull black. Let dry. Then do an overcoat with whatever paint you wish. My personal favorite is the black gloss. The black gloss not only looks good, but the water beads up on it, perhaps offering some additional protection.

I do this every Spring, once the temperature and humidity is such that the undercarriages on my vehicles can take the wire brush and powersprayer tx. I will remove the spare tire first. I typically will do a good wire brush tx. Go to one of those coin operated, manual car washes, with the degreaser, high pressure soap, high pressure rinse. Then the drive home usually will have it dry before I start spraying on the Rust Converter/Primer. By the time I am finished spraying from the rear to the front (or vice versa), it is ready to start spraying on the gloss.

I'll keep an eye on the weather as Summer turns to Fall. Once it starts to get cool again, but still within the recommended temp. for the paint. I will touch up any areas before the snow starts to fall in November.

Another tip: I found ACE Hardware carries a food-grade Silicone Spray (no petroleum distillates), that dries pretty quick, and doesn't stay wet. I will coat the undercarriage and suspension parts/bushings, etc. before the snow starts to fly.

That's exactly my plan. It'll also be the solution to coating the inside of the frame rails that I can't get to with converter to keep them free from any more rust

Sounds like a good plan. I have tried Rustoleum on my parent's 2001 Tahoe and found that it doesn't quite stand up like the Permatex I'm using does. In any case, even doing a short term solution over and over again is better than nothing

undercoating with fluid film - YouTube

I think if I were to use it, I would try to get a nozzle spray attachment and get into all the holes in the frame rails, etc. I don't really care for the look of it, but if it really works well, I might have to change my ways. I might try it this Fall, though.

I like the look of my gloss black.

I use FF on my 3rd gen. I have the hose with both the straight-shot nozzle and the 360 degree sprayer for inside the frame rails. Never had to use anything else.

[IMG]5 by Skinfaxi, on Flickr[/IMG]

Does the Fluid Film eventually dry or does it leave a sticky film?

Can it take a top coat of paint?

I am not a big fan of anything that leaves a sticky residue that can attract road grit.

It never dries, but it's not sticky, sort of like a smooth wax. I just hose off the undercarriage with water to get the big clumps of dirt off and spray it on before and after winter. No rust yet. Can't top coat it, don't really need to.

POR-15 is the best you can buy. Also the most expensive. But you don't have to apply it every year.

It's really only good for spot treating already rusty areas, not for preventative use. If you want to coat the entire underbody (metal stuff at least) it will take several full days of work, and you'll never hit all the areas unless you remove the frame completely. That said, I've used it in the past to paint over bad spots on other vehicles and in that regard nothing compares. Combination of POR on the bad spots and fluid film sprayed on top of everything is the best thing you can do.

I could be wrong but I think POR-15 has better resistance than anything else I've seen.

Problem is it doesn't stick to rust-free metal, it will flake off. It's designed to chemically bond to rust, which is why it's awesome for already rusted areas, but not for already clean frames. I painted some preventatively on my BMW and it came off after about 2 years.

I primarily use Fluid Film because you can see through it and know exactly what's going on with the metal. Painting over it is an out of sight out of mind approach. Just because you can't see the rust anymore doesn't mean it's not still spreading. And if it does start spreading, you now need to grind off tough as nails paint to fix it again. POR 15 will stop rust in its tracks, but good luck being confident the inside of your frame rails aren't heinous. With FF, it's dirt cheap to coat everything, everywhere, inside and out, multiple times a year. Takes about an hour with a spray gun. One gallon will get you 4 complete applications. If rust starts anywhere, spot treat it with POR, but I wouldn't paint the whole thing in POR and forget about it. It will be a nightmare to correct anything down the road.

Agree with the POR-15 comments. I've used it on my '89 Mustang during some resto-mod work. As said earlier, though, POR-15 application is definitely a process and does take a fair amount of time (days) if you are doing it correctly.

The other downside is that it is quite difficult to get into those tight areas, because, as far as I know, this is a brush-on application. I still think that one would benefit from something that can be sprayed on, as it is more likely to reach all those tough-to-get areas, especially if one used some sort of flexible nozzle.

I might try to get my hands on some Fluid Film, at least for the frame rails, inner bumpers, and that constantly rusting skid plate.

Seems like you could do a nice undercoat after the fact. I just bought a 4th gen and I will probably go that route.