Undercoating

What is the best product to use for general undercoating. I have heard Krown, Fluid film, Pro 15 and so many more. Can anyone suggest the best for a DIY?
Thanks

 

Cosmoline

https://www.cosmolinedirect.com/cosmoline-rp-342-heavy-spray-military-grade-rust-preventive/

 

thanks rustygreen

 

About how many cans to do a thorough job?

 

I just went to rustygreens attachment and it gives you a chart and information on how many cans you will need.

 

Yes,found it,thanks.

 

Recently had Krown do mine (prior to winter).
They did an excellent job and walked me through all my questions and concerns. They will put your truck on a lift and spray every nook and cranny.

 

Woolwax (thicker fluid film)

 

I've used Woolwax, Fluid Film, RP-342, and Eastwoods' cosmoline over the years. I would not recommend anything that dries hard.
I have a bulk sprayer, but if you don't have access to a lift like me I find the aerosol spray cans with the two-foot 360-degree tip easier to use when you're on your back with a mechanics creeper.

 

I like to do mine when it's really hot out. I'll start with something thick like Fluid Film then follow up with something a little thinner to help wick the thicker stuff into the sandwiched parts of the frame. I also spray up into the weep holes in the pinch seam at the bottom of the rockers and cab corners. Then, I spray up into the drainage holes in my doors. I also spray up into the box sides and front fenders above the wheel and let it run down into the fender behind the flares.
When it's really hot out, I'll even get little trails of oil up the outsides of my doors. That tells me it's creeping up into the doors as well.
I've even removed the inner panel of my tailgate and sprayed well in there. You can just spray into the drain holes there. If your body panels are going to rust, it will start at the seams in the bottom where the two layers are rolled together.
My truck is a 2014 and it it pretty much rust free.
Get it up on ramps or jack stands as high as you can, just be safe! And wear eye protection. Some type of N95 mask would be a good idea too. The stuff doesn't taste good...

 

Took 9 cans for me and I went overkill.
Chose cosmoline because i don’t want to apply it yearly like you have to with FF and WW

Why not?

 

Anything that dries hard will eventually crack and then trap moisture against the metal, making rust even worse. Unless you're coating the dried stuff with something like Fluid Film, but that defeats the point of having it in the first place.

 

Ahh I understand. I wouldn’t think cosmoline would crack but I’ve only used it for one year so far. Have u seen it eventually crack? I know rubberized coatings are notorious for cracking

 

Hey OP, this should help you make your decision. And welcome to TW!

https://youtu.be/oXlhmbvdKBo

 

Broadly speaking these these products fall into 3 categories: waxy, oily and rubbery/asphalt -- all are available in standard aerosol cans. To prevent rust you need a barrier between the steel and the enemies: moisture and oxygen, all the products attempt to achieve this.

Waxy: Ex: Cosmoline, sprays on as a thin, penetrating liquid and dries to a soft, pliant barrier that is fairly difficult for road debris to scrape off. Since these products don't set hard like paint they don't chip and are said to be able to "self heal" some if scuffed. These are the longest lasting products.

Oily: Ex: Fluid Film, very similar to coating the bottom of the truck with engine oil, the advantage is that they are very good at creeping in to seams and hard to access areas. The disadvantages are they make a mess under the truck, you can't touch anything under there without getting filthy between the oil and the dirt it holds. These products do wash away over time and need to be reapplied every Fall.

Rubbery/Asphalt: Ex: Parts store undercoat spray, these products are typically thicker and provide sound deadening, many older cars (1960's-80's) had the asphalt style of undercoat from the factory. The high solvent formulas of the day were very durable.
These products set from very firm to hard and here lies the problem -- they crack and chip. This allows moisture in with no way to escape, everything looks fine until the bond is so compromised that a big chunk falls off and reveals the damage that was cooking behind it. Stay away from these products and never buy a used vehicle with a nice fresh undercoat job either, they did that for hiding not protection.

This is a great video on the topic, this fellow does a lot of product testing without bias, he does not accept anything from manufacturers, purchases everything himself.

https://www.youtube.com/watch?v=lyWHF4NoNVk&t=3s

 

Cosmoline stays mostly viscous. Good stuff.

 

Cosmoline doesn't set hard, it remains pliant -- it won't crack.

 

Woolwax. I've used it myself now for 2 years and it's great stuff. @bob1008 is a member here on TW too!

https://www.tacomaworld.com/threads...ves-to-fluid-film.466404/page-6#post-26529879

 

I plan to give New Hampshire Oil Undercoating a try this spring as we have a NHOU dealer in western MT. AMD, "The Car Care Nut" YouTube channel, a Toyota Master Diagnostic Technician who works at home with his wife as videographer, in addition to his day job at a Chicagoland rust belt Toyota dealership, responded to my chat during a Saturday live stream that the plan for rustproofing the frame is highly recommended because "Toyota trucks need it!" The other Toyota/Lexus vehicles are pretty well sealed and protected with plastic. That channel is a great reference, with two playlists on the Tacoma, and more on various systems and maintenance.

 

This guy is great I watch alot of his reviews