Best way to keep a truck from rusting

Although this comment doesn't apply specifically to trucks, a common place for corrosion is the body panel right above the rear wheel. There is often a little shelf (a panel stiffener presumably) right above the rear wheel well that collects dirt, water and salt and keeps that mess in contact with the inside of the body panel.

I wash whatever part can be reached from the real wheel opening. There is usually a bunch of debris up there.

Keeping that area clean is a big step toward reducing corrosion.
 
It really takes a lot of work to keep rust at bay in the salt belts. For me, it was twice a year applications of fluid film with something heavier on the higher exposure areas, like white lithium spray grease, cosmoline, regular grease, chain lube. That type of heavier stuff.

But once you already have a rusted frame, there’s not a lot you can do to stop it. You could go through all the trouble of grinding it off, and then apply your rust prevention on top of it. Or you could simply spray something pliable on it and hope for the best (Fluid Film, Krown, NH oil undercoating, etc). But either way it’s a battle that only lets up in the summer months.
 
I have a 3rd gen Ram and I buy a monthly car wash plan at my local car wash. It has a "Bottom Blaster" and it seems to work to keep the crud off under my truck. I have 221K on my Laramie Hemi and It is very clean under it. I can get it washed every day if I want to on that $29.95/mo plan. It is worth it to me especially when I go under it to change fluids and it is clean.
 
It really takes a lot of work to keep rust at bay in the salt belts. For me, it was twice a year applications of fluid film with something heavier on the higher exposure areas, like white lithium spray grease, cosmoline, regular grease, chain lube. That type of heavier stuff.

But once you already have a rusted frame, there’s not a lot you can do to stop it. You could go through all the trouble of grinding it off, and then apply your rust prevention on top of it. Or you could simply spray something pliable on it and hope for the best (Fluid Film, Krown, NH oil undercoating, etc). But either way it’s a battle that only lets up in the summer months.
100%. I stopped using FF, Rust Check, Krown, etc. as they wash off far too easily. It would take 2 or more applications of these products yearly or more to provide protection. Rust Check is pretty much gone from any exposed surface after an hour driving in the rain. The reasons I use the Noxudol (over the myriad of other products I've used) are twofold:

1. The 300/700 does not wash off and 300 only needs minor touch ups (200-300 ml of product) once yearly in heavy blast zones, typically right behind the wheels.

2. Noxudol 300/700 does react with existing rust. The long term test here touches on that behaviour specifically. It's also I suspect why OEMs like Toyota have used it repeatedly in their corrosion related recalls:


It does take longer to do a good job of application as ideally you would pull fender liners etc. to get good access to everything. Initial cost is more at $28/quart, .but overall running costs are much less as you're not fully applying the product yearly. Every car I've pulled apart has corrosion "hot spots" but there is a common issue I see behind the front wheels in the wheel well. Very often leaves/seeds etc. from the windshield make their way to the fender drains (in the wheel well, behind front wheels) and very often these drains are plugged up so a wet mess of organics/mud etc will sit there and create rust issues. It's pretty much impossible to clean these without actually pulling the fender liners which is a job that ranges from easy to a real PITA depending on the clip design. The Audi A3 I owned used no less than three pieces in the fender liner...

2 days after application the Noxudol 300 and 700 is still quite wet, which is a good thing. It has no solvents..so the upside is a lot of seam penetration as it slowly cures. These pics are from a 2018 LEAF EV.

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This is the assortment of cavity gun tools that I use. The small tip is used the most as the largest surface is typically exposed chassis. That longer rod is handy for rear quarters, doors, and truck bed sides via the tail lights.

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Noxudol 700 for underneath and frame and 700 for all the inner panels and between the bed and outer panels, this is the best by a long shot.
 
Another fan favorite is WoolWax. Last I checked they were asking 400 for a tahoe size suv. Resprays are every 18 months, they take 6 hours to first pressure wash and air dry the undercarriage. Then apply woolwax.
 
First time hearing Noxudol. Cosmoline is another option. Tacky and used by alot of German mfgs before they moved to more eco friendly wraps and other tech.

I think if you are DIYing Cosmoline seems to resist being washed off the most. They dont seem to have any application centers, at least none they openly advertise unlike FF, Noxudol, Krown etc.
Just to add Cosomoline was used as a shipping rust inhibitor that was later washed off at their Vehicle Prep Centers after coming off the RoRos
 
Amsoil makes a good rust proofing spray.
In my CPC research, I was only interested in actual long term tests, and an analysis of the chemical composition. If it washes off easily, and/or is just thickened lanolin, not so interested. The litmus test was then actual use on vehicles, in salt and sand conditions along with demonstrated panel creep in warm weather etc. Mike Sanders grease is something I also use, but the whole 120C application process is a real PITA, and panel creep requires higher temps. The higher application temps means though that it does not wash off at normal temps. I use Woolwax on my snowblower for summer storage, but that's about it.

I've yet to see a vehicle in our area with zero rust, so how a product performs over existing corrosion is very important. Even a new vehicle will take rock hits on the undercarriage and how the product both heals and arrests rust is another major consideration on long term vehicles. If you're leasing, none of this applies :)

Noxudol does require a few days to set up, but once there, the much easier application along with known additive packages make it my goto product now. Toyota, Subaru, Isuzu etc. must have thought so to, as that is what they spec it specifically in numerous TSB recall docs. I also think that having one product that has high mobility/creep for panels, but also can withstand exposed chassis conditions is pretty much impossible...this is where most coating systems fail IMHO.

Every one of the OEM TSBs I've reviewed, where chassis/frame treatment was required, used two products. One product for inside frame rails/body panels (thinner, higher creep), and a heavier body product for external exposed chassis. The franchise rust shops just don't do a good job in the time frame allotted, and the product they typically use just washes off after even a short drive in rain...complete waste of time/money IMHO.
 
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Got interested in Noxudol.

Process takes 2 days from start to finish, pressure underside
Lifetime warranty, and once and done process.
Cost for an SUV $900
 
That sounds about right...but you'd want to make sure of a once yearly check for small touch ups on the chassis. Also a good idea to avoid rain if you can for 4-5 days. It takes me 6-8 hours on a car to do it properly. Material costs about $200.
 
I spent about 450$ on noxudol for my F350. I haven’t sprayed it yet (some time in October likely due to hand injury). I have some 700 (inside of homes frame/body cavities) and 300S for everywhere else (Toyota branded). I plan on pulling both front and rear bumpers off, wheel well liners, fuel tank, possibly DEF tank also and anything else that may Inhibit access. I’m going to pressure wash/degrease everything including inside of chassis (oil undercoated 1 year ago) and then spray. Probably will take me a couple of days. I’ll post photos when I do the job. I was also turned onto this by @denwood
 
I use Woolwax on my vehicles. My 95 GMC was purchased with typical New England rust but I have coated the frame yearly without issue. I check it in the Spring and touch up any spots where the coating washed off. Another thing I'd recommend is going after rock chips immediately. A quick sanding and touch up paint can save you a lot of work down the road.
 
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