Found this when searching for issues with plating failing on hydraulic hose ends exposed to the common salt brines used these days to control ice on snow belt roads. I plan to eventually use my 56 Dodge/2001 Dakota as my daily driver up here in east central Wisconsin. So after the cab/box/Dakota cab floor/firwall is done on the 56 I'll need some form of undercoating to make sure the truck lasts for many years to come. I'll install full fender liners and other methods to minimize snow/ice/salt buildiup in the critical areas underneath, but an undercoating will still be needed. I found this product:

https://nhoilundercoating.com/faq-undercoating/

If its as good as claimed it could be my choice. Anyone else have experience with really good DIY undercoating to protect our vintage rides from the modern salt brines?

Found this product too: https://www.krown.com/en/products/aerosols/rust-protection-lubricants/

Decades ago Ziebart was the go-to. Not so sure that applies anymore. Ziebart was/is a hard coating that can age, flex, crack. As soon as a crack appears it becomes a salt/moisture trap.

I just bought and tried the NHOU product this past fall, I haven't had it on there yet long enough to tell if it will live up to the hype. I bought a 5 gallon bucket of their black stuff and their estimate was 6 quarts for a 1st time application, I used 10. (1/2 of the 5 gallon bucket) and I didn't get to pull the door panels or the tailgate access panel and get inside those like I wanted to.
Luckily we here In the Chicago area have had a mild winter, not as much salt used to this point as A typical winter.
And every time I thought they "might" I have left it parked (outside on a concrete driveway) and took my beater Dakota that's already beyond hope anyway.... But I hope it does as they say. The truck I put it in, is a 12 ram 1500 reg cab long bed, former Fastenal truck. I still owe 3 years in a 4 year loan and as expensive as trucks are I sure hope it does as they claim
I removed the plastic fender liners, the tail lights and blew out all the leaves and such that I found hiding beneath all that and all the dirt up high into the rear bedsides and blew NHOU as far up into the bedsides as I could reach while I had the truck up on my 2 post lift.

For what it's worth - I have some experience with the Krown rustproofing product. I take my Ram and Durango to a location near me on a yearly basis and they apply it throughout the vehicle. It's a slightly viscous, oily liquid that clings to metal and creeps into crevices well. That's why I think it has held up so well for me and protects areas like pinch welds, fender lips and cavities like rocker panels and cab corners. Those are the areas that I was mostly concerned about.

In my opinion, areas like the bottom of the floorboards which are subjected to water splash and abrasion would do better with something thicker than the Krown product. Even though I haven't seen any rusting on those areas yet, I feel that they need a thicker barrier coating that prevents chips or scratches.

One more thing to mention - if you use the Krown product on interior cavities (like rocker panels), expect some to seep out of the drain holes. That's not a bad thing, it means that the liquid is creeping into all of the crevices. Any product that drains out is easily wiped off and doesn't stain paint. The only thing you need to be careful around is if the product soaks into rubber. It can cause some types of rubber to swell.

Hope this helps.

Thanks for the detailed responses. When I do my 56 Dodge pickup onto my 2001 Dakota donor frame/floorpan/firewall I may clean and repaint the bottom side of the floorpan, then coat it with pickup bed liner product. Then use some of the products mentioned above to do all the seams, corners, crevices etc to let it creep/seep into those areas. Do either products give off any kind ot smell? I am very tolerant to the usual automotive smells, bodywork smells, fiberglass, etc. My wife, err not much at all.

Hi,
The Krown product has a mild smell sort of like vegetable oil. Not pungent or overly strong. Your wife may initially smell it when it drips out of weep holes, but after that you should be fine.

I use corrosion free, that far north you should be able to find it (its Canadian). Its clear, has no smell, does not drip and is durable. It will still be there in the spring unlike many of the other product I have used.

https://corrosionfree.com/find-a-dealer/

A quality oil spray is the best thing you can use. Dont use any rubberized product that traps moisture and causes it to rust from the inside out. I have also used Krown, its a thinner product that CF and half of it dripped onto my driveway because it was a new car (painted bottom). Krown may work better on a pre rusted surface?

All great info. Thanks for the perspective on the Corrosion Free versus the Krown and and other products.

I got my 2001 Dakota used from a friend who had bought it new. So it survived ten Wisconsin winters before I took ownership. It had the usual snow belt rust, rockers, bed fender openings, door bottoms. I did my driveway rust repairs the down and dirty way, spray foam, fiberglass, pickup bed liner and paint where exposed. It did ok, looked solid/decent from a distance, but eventually the ravages of rust move on. One thing that did make a difference; I flushed out the areas around the front fenders, around the door hinges areas, other similar areas, let it dry and then sprayed WD40 liberally into those areas. Been doing that since spring of 2011 and it has slowed the further progression of rust.

Once I get my vintage 56 cab/box on my Dakota chassis, I can apply the products above in like manner, and should be able to hold off most of the snow-belt/salt-belt attack. If i were buying a new pickup I would certainly do likewise on a yearly basis and I bet it would survive MUCH better than just being exposed as is from the factory.

I discovered Krown when stationed in North Dakota--it is good stuff in the right application. I still use it on my daily drivers.

It excels inside body panels in tight pinch-weld type of areas that tend to collect water and debris--on top of pickup truck rear wheel wells, inside doors especially on the bottom pinch weld where the skin meets the frame, rocker panels, trunk floor extensions and inner fenders where they meet the quarter panel.

It is not as good in large, open areas like the bottom of floor pans.

It does need re-applied occasionally.

As said above, an oily product that does not dry or harden is your bet bet IMO.

Glad I don't have to work on stuff covered in oily residue.

Can't argue with that, but dealing with oily residue is easier then dealing with crusty rusty residue.

I had a truck that I bought cheap ($1200) that was fairly clean underneath. I mostly drove it through the winter in the salt and slush, then to make matters worse, through most of the summers when it wasn't being used as a truck to haul stuff, it got parked on the grass along my driveway. In a matter of 4 years, the entire bottom of the truck was a dark brown rust color. The rust was bad enough in those 4 short years that nothing bolted together under the truck came apart with out breaking the bolts. I felt fortunate that nothing serious under the truck needed done before the frame rotted out bad enough (at about 6 years) that I junked the truck. From up above the truck looked pretty good, but it wasn't. Not sure an annual oiling would have help that one much, but I could see where it might be helpful with my 49.

Can't argue with that, so I live where I don't have to deal with either. I've grew up where that stuff was common, no more.

Krown application

https://www.youtube.com/watch?v=kKmM5IByVCQ&t=143s

A little annoying, yes. But it wipes right off.

I'll take a little oil over working on rust any day.

I've found a side effect of the Krown is that it keeps suspension nuts and bolts and components from seizing.

I used Krown for a couple years then swithched to Rust Check which is the same idea but has been around longer. Maybe 10-12 years ago they started using a different formula for under body that is thicker and lasts longer. No matter what gets used you can definitely see what cars have had some sort of treatment and which ones haven't.

I guess the corollary is that I am glad I don't live were the state is actively trying to destroy my stuff with salt. Just redid the suspension on my 51 Plymouth, zero rust, zero seized nuts or components.

I can't imagine how y'all put up with that.

Don't have much choice, Park your vehicles in the winter or move. I am opting for #2.

i live in good old putzelvania, and they just LUV to use salt and salt brine to slather over everything.
my trusty "bus" [99 caravan] gets a real good "oiling" every year, done by my buddy's shop.
it then leaks oil like an old harley until it gets done the following year.
i drilled a ton of extra holes in the doors and the hatch, plus above the foam in the dog legs and rockers.
i pick a day when it's not raining to get this done. i show up early, then remove all the plugs, plus the tail lights, so the inner 1/4's get a good dousing as well.
the hood gets blasted into the forward edge through the crush zone holes.
the bottoms of the front fenders have had most of the foam removed, so that area gets hosed good as well.
cost is roughly a little over $100.00, depending on his cost of materials.
i have WAY more money in oil than i paid for this thing 10-12 years ago !
but it still ain't rusty !

I used Por 15 on my rusted framerails on my 69 roadrunner messy but worked pretty well.

I use a lot of that, I haven't seen a lot of what I've used it for long term (that's been exposed to the elements anyway) but on our Durango I replaced a fender about 10 years ago from a deer strike and I slathered POR15 on the inside of the replacement fender to (obviously) protect it as long as possible and recently I was in there and was looking around, it seems to have peeled on the inner reinforcements behind the battery and I see a good bit of (hopefully only) surface rust on the back side of the fender

Eastwood Heavy Duty Anti-Rust seems like a good product for this rust prevention problem? It's like a waxy coating or cosmoline basically.