Underbody coating and corrosion protection | Ford Explorer Forums - Serious Explorations

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Underbody coating and corrosion protection

On my "to-do" list for a while has been the task of taking care of the under-body of my truck. I want this truck to last pretty much forever, so I wanted to make sure that rust wouldn't lay claim to too many parts too early. Being in the rust belt, it happens too easily, and I've already seen it taking hold. So, I formulated a plan of attack to help stop/slow this whole process. It had a couple of stages:

1) Power washing to remove all dirt, mud, grime
2) Rust scraping/removal
3) Rust reformer treatment
4) Sealing with anti-rust/corrosion chemicals

I started it a few weeks back with a power wash of nearly everything I could reach under the truck. I gave it a real solid blasting to remove as much mud & dirt from off roading as possible (DAMN that is stubborn stuff! :eek:).

Next, I crawled under and did my best at scraping and removing as much rust as possible. The inside of both of my bumpers were breaking apart in huge chunks of corroded, rusted metal. I scraped away as much as I could and then hit it with a wire brush and a wire wheel attached to a drill to really dig through it.

I then treated the rust with one of those "Rust reformer" chemicals which stops rust development in it's tracks and cures it into a hardened, paintable surface. There's a picture below of the one I used. It worked really well. I also had rust problems on my Warrior shackles, as moisture had gotten under the powder-coat from dings and dents and I had to peel it off and treat them. I could also see rust starting to form in the seams of the body sheetmetal, my Rancho shocks were in bad shape, etc. A lot of rust to handle, but I think I did a solid job.

Finally, I needed to seal everything. I did a lot of reading on the best products and brands for this, and finally settled on 2: Amsoil Heavy Duty Metal Protector, and Fluid Film protective lubricant. The Amsoil spray is advertised as a "dry" lubricant which serves very well as an undercoating, and includes rust and corrosion inhibitors. I've read nothing but good things about this product, and if the reputation of the brand is anything to go by, it's a winner. I hit almost the entire underbody of the truck with this stuff, from the frame rails down to the shocks and sheetmetal. It came out like an oil when spraying, however, after a little while it dried to more of a sticky wax-like coating - as advertised. It wasn't dripping or wet-looking anymore, and it was almost tough to tell where you sprayed it because of that. The only issues I have are that to remove it, you need solvent, and that could make future work on the truck a sticky, oily endeavor. Additionally, Amsoil claims that it doesn't attract dust, but I found it to still be sticky a day or two after application, so I can't imagine it not ending up attracting grime and dust and being a bit of a mess. That being said, I really like the product.

The Fluid Film coating I didn't care for as much. It's a thin lubricant meant to penetrate and coat and protect metal and metal parts, and it came out oily and stayed oily. It didn't "dry" like the Amsoil, and left everything greasy and shiny. It claims to not wash off very easily, and obviously being an oil I would expect this to be true, but without it drying like the Amsoil, I have a hard time believing it would last nearly as long. On the positive side, it is a thin oil, and is pretty good at seeping into cracks and coating thoroughly. In my opinion, the best use for the FF would be to apply it after the Amsoil has been applied and has dried, so it can seep into any spots you couldn't reach and serve as an extra layer of protection - and if/when it comes off, you still have the Amsoil barrier. I'm sure it's a very effective metal protector, as I've read nothing but good things, but when compared to the Amsoil, I'm not so sure it's as effective as a long-term undercoat, which was what I was after.

I won't really be able to tell any results for a while, but I'm overall happy with how things went, even thought the Amsoil made my truck smell like a giant crayon. :D When all was said and done, I used 1.5 bottles of Rust Reformer, 3.5 cans of the Amsoil, and 1 can of the Fluid Film. I might swing back under in a few weeks and empty the last can of Amsoil and throw some more FF on it to be safe, but we'll see. And as a side note - it was really nice to have a body lift during all this - the 3'' of extra headroom and more light under there made it easier than it otherwise would have been.

The stars of the show:


Heres a photo of a section of the underbody that was completely rusted, but was treated with the reformer - it turns hard and black/brown:


Some of the spray, still wet on the underside of the body:


Underneath in the rear:


Frame rail:


Inside of the front bumper (didn't scrape or treat that bracket for rust):


Will add a few more pictures later.

just got an 04 nbx. doesn't have much rust i am definately gonna try this stuff. how long did it take? how carefull do you have to be around moving parts, exhaust etc?

I've read that you can spray it on pretty much anything. It's fine for moving parts, as it's also a lubricant. I did my best (which wasn't that good, haha) to avoid rubber and plastic, but I'm not sure it matters much. I also hit my muffler with it and most of the exhaust system except the cat. No issues. My truck did smell like crayons for about a week, but it's fine now.

As for time, it really depends on how meticulous you want to be with it, if you can get your rig on a lift, etc. It took me a couple of hours working on my back in a parking lot.