Underbody rust

[Jebiruph]

Last year I noticed rust starting on the underside of the rocker and the side step brackets of my 2018 JL.

I checked my 2020 JT and it was having the same issue. It looks like the thin paint on the inside edges of the square cut outs splits and peels, exposing bare metal.

Based on recommendations from local body shop supply stores, I use a product called Phix to treat the surface rust https://ppcbest.com/phix-corrosion-treatment/. It doesn't convert rust like other products, it removes it. After cleaning up the rust I painted it with Satin Coastal Gray Rustoleum.

It's been a year and it seems to be holding up.

For the step brackets, I just bought and installed new take off steps after some preventative painting of the metal parts of the brackets with a couple coats of Rustoleum.

I was relying on my Sahara side steps for protection from road splatter on the visible surfaces, but after finding this rust I added mud flaps to help protect the underside.

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[JerseyJeff]

Go on amazon. Get some "fluid film". If you don't have an air compressor get the cans and spray the underside of your jeep don't forget the nooks and crannies. I did that to my previous truck and both my jeeps. It will keep your metal from corroding. Watch some youtube videos about it.

 

[Jebiruph]

Go on amazon. Get some "fluid film". If you don't have an air compressor get the cans and spray the underside of your jeep don't forget the nooks and crannies. I did that to my previous truck and both my jeeps. It will keep your metal from corroding. Watch some youtube videos about it.

Do you use fluid film to treat rust or to prevent rust? I thought if you sprayed fluid film over existing rust you would make it worse due to trapping moisture with the rust instead of allowing the moisture to evaporate away from the rust.

 

[JerseyJeff]

Fluid film displaces water. It is a petroleum based paraffin wax that does not get hard or dry out. It can wash off certain surfaces that would be subject to repeated splashing forces of water but then you only need to reapply to those surfaces. A yearly touch up is recommended.

 

[WindyCityWilly]

Try WoolWax instead of Fluid Film. I think the same company makes both, but Wool Wax is thicker and doesn't wash out nearly as easily. As a general rule if it's exposed - like frame rails - I use Wool Wax. If it's inside an enclosed cavity - like a door - I use Fluid Film.

 

[Jebiruph]

There are plenty of fluid film and similar rust preventative coating threads on this board, this thread is about finding and treating existing rust.

I would not recommend applying fluid film over existing rust.

 

[its_overson]

There are plenty of fluid film and similar rust preventative coating threads on this board, this thread is about finding and treating existing rust.

I would not recommend applying fluid film over existing rust.

I mostly agree. The best solution would be to remove the rust then treat the area but if you're not going to do that, Fluid Film actually works pretty well on areas that already have light rust. They even speak to that in the FAQs on their website: "FLUID FILM is not formulated to remove rust. However, if applied over existing rust, it will stop it immediately from spreading further. FLUID FILM will penetrate rust and rust scale to the base metal, loosening and easing in the removal process."

I only mention this because not everyone is going to take the time to do it "correctly" and fluid film is better than nothing. USMC uses it on most of their tactical wheeled vehicles and the difference between a vehicle that's been treated and one that wasn't is significant.

 

[Jebiruph]

I mostly agree. The best solution would be to remove the rust then treat the area but if you're not going to do that, Fluid Film actually works pretty well on areas that already have light rust. They even speak to that in the FAQs on their website: "FLUID FILM is not formulated to remove rust. However, if applied over existing rust, it will stop it immediately from spreading further. FLUID FILM will penetrate rust and rust scale to the base metal, loosening and easing in the removal process."

I only mention this because not everyone is going to take the time to do it "correctly" and fluid film is better than nothing. USMC uses it on most of their tactical wheeled vehicles and the difference between a vehicle that's been treated and one that wasn't is significant.

I wasn't aware of Fluid Film's claim of preventing existing rust from spreading. My recollection from previous discussions was the recommendation to not spray over existing rust.

 

[Jebiruph]

There are plenty of fluid film and similar rust preventative coating threads on this board, this thread is about finding and treating existing rust.

I would not recommend applying fluid film over existing rust.

Upon further review, maybe this thread is about treating and preventing rust from the perspective of an untreated 5+ year old JL and an untreated 3+ year old JT.

Knowing what I know now, if I was going to apply some kind of coating to the underside of my new Jeep, I would focus on the underside of the rocker panels. The square cutouts and seam are the only places where I've seen any rusting of the under body sheet metal.

After I spotted the rust on the JL rockers, I decided to treat the seam on JT rockers. I should have put it on the ramps to get more clearance before spraying., I ended up being too close and sprayed it on thicker than I intended.

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