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Undercoat or not to undercoat?

Ev3nter999

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Wondering if anyone has gotten undercoating done and how much you paid? And wondering what the best possible product was that was used.
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Dialtone

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Wondering if anyone has gotten undercoating done and how much you paid? And wondering what the best possible product was that was used.
Search the threads. There are a few with some excellent recommendations
 

CrazyPete

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I used to take our trucks to Krown for several years and it looked great underneath. But, with the Bronco, i did it myself with Woolwax. 👍
 

OuterJersey

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I did some randomness with surface shield which seems to be wax
 
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eugenemoyer8

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Save your money do it yourself you'll get a better job these people doing rust proofing today just hurry up and they miss a lot of spots
 
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timbits588

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I used to take our trucks to Krown for several years and it looked great underneath. But, with the Bronco, i did it myself with Woolwax. 👍
@CrazyPete How do you like the Woolwax? I have been debating between Krown and doing it myself, as well. I have never used Krown, but have a friend that swears by it. I've used POR-15 in the past, but never a wax/oil coating.
 

indio22

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I used to take our trucks to Krown for several years and it looked great underneath. But, with the Bronco, i did it myself with Woolwax. 👍
How did that go for you? I sprayed my TJ frame with Wool Wax, using a decent sized compressor and their dedicated applicator gun/wand. I got it applied ok, but felt the spray pattern could have been better. Maybe I need to either heat it up, or cut it down with something.

A guy I know uses Fluid Film, and cuts it down with WD-40. Which seems questionable- but he claims is works great and flows into the nooks and cracks better that way.
 

Fly by Nite

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Avoid the old style asphalt undercoatings. They will eventually trap moisture and increase corrosion.

An annual application of a product such as Fluid Film/Woolwax works well. It soaks into crevices treating areas most prone to rust. There are others such as Surface Shield and Waxoyl, and even old school Cosmolene that are kinda similar.

I used Fluid Film on my XJ Jeep. It performed well, treated existing rust and helped prolong metal life. However, it's like treating the underside with slime. A little messy when you need to do maintenance work underneath. It can be powerwashed off (mostly).

For my Bronco I'm going to try Waxoyl. It's a harder film, which I expect to better maintain factory appearance of components. I'm a car/car show/restoration guy so I want to maintain this thing to keep it looking new for a few more decades.
 

Doc TOC

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Under coating, at best, is an uphill battle. At worst, a scam.
Dealerships no longer do it because they have been sued so often.

Oils, waxes, and oil/wax/thinner combos are hydrocarbons (asphalt is an oil). As the oil's aromatics evaporate, the oil solidifies to what is commonly referred to as a wax. The wax will adhere to metal, for awhile. That is why many people annually retreat the undercarriage in fall. But the oils/waxes are not long lasting - they do not bond to metal, like salt and water will. This is basic chemistry and physics.

True rust protection actually requires "pre-rusting" the metal. As in stainless steel, where the nickel forms a molecular layer of rust. Like Cor-Ten steel used on bridges, architectural balconies, etc.

[EDITED: listed the wrong product. My bad.]
For the cost of constantly re-undercoating, you could be one-and-done with a true metal bonder like Corroseal Metal Master Primer. There are other brands out there. Rustoleum is another brand. Only the metal parts are treated. Plastics don't need sealing because they are hydrocarbons (naturally water repelling).

Rust prevention is a manual, hand process. You have to rotate shafts, get the top side of axles, avoid zinc, stainless or copper, not ruin plastic with hydrocarbon leaching, not destroy your wiring's shielding, etc. And the hi-temp metal parts (1) will burn off the hydrocarbon coatings, (2) are damaged by pre-rusting, and (3) instead should be coated with a high-temp paint designed to handle the metal's expansion and contraction.

It's not so much the water, as it is the mineral salts that attack the steel. Those are on the road all year round. In higher concentration when snow gets salted. And waxes will pick up the salts and store them 'in suspension'. A regular trip to the car wash with undercarriage sprayers may be more useful.

Your money and time, your choices.
 
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Fly by Nite

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Under coating, at best, is an uphill battle. At worst, a scam.
Dealerships no longer do it because they have been sued so often.

Oils, waxes, and oil/wax/thinner combos are hydrocarbons (asphalt is an oil). As the oil's aromatics evaporate, the oil solidifies to what is commonly referred to as a wax. The wax will adhere to metal, for awhile. That is why many people annually retreat the undercarriage in fall. But the oils/waxes are not long lasting - they do not bond to metal, like salt and water will. This is basic chemistry and physics.

True rust protection actually requires "pre-rusting" the metal. As in stainless steel, where the nickel forms a molecular layer of rust. Like Cor-Ten steel used on bridges, architectural balconies, etc.

For the cost of constantly re-undercoating, you could be one-and-done with a true rust bonder like Corroseal. There are other brands out there. Rustoleum is another brand. Only the metal parts are treated. Plastics don't need sealing because they are hydrocarbons (naturally water repelling).

True rust coating is a manual, hand process. You have to rotate shafts, get the top side of axles, avoid zinc, stainless or copper, not ruin plastic with hydrocarbon leaching, not destroy your wiring's shielding, etc. And the hi-temp metal parts (1) will burn off the hydrocarbon coatings, (2) are damaged by pre-rusting, and (3) instead should be coated with a high-temp paint designed to handle the metal's expansion and contraction.

It's not so much the water, as it is the mineral salts that attack the steel. Those are on the road all year round. In higher concentration when snow gets salted. And waxes will pick up the salts and store them 'in suspension'. A regular trip to the car wash with undercarriage sprayers may be more useful.

Your money and time, your choices.
I wanted to address your post as it may be misleading the OP towards a product which doesn't address their concerns.

What you are describing (Correseal) is treating existing rust by converting it into another compound..... which will need to topcoated/painted.

Undercoating has a different purpose..... to provide an additional layer to repel water and moisture, and give some protection from minor impacts such as dirt and stones kicked up which can chip painted underbody components and lead to rust and eventual coating/paint failure as the rust spreads.

Now if ones goal was to touch up surface rust on a new vehicle and paint those areas, fine, Corroseal is a choice for spot treatment. But it's not going to prevent rust elsewhere, that's what undercoating is for,

FluidFilm/Woolwax is Lanolin based, a natural product produced by sheep to waterproof their hides.
 

Doc TOC

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@Fly by Nite - I suggest re-reading the post.

Metal Master Primer is used as a rust preventer. It contains an acrylic polymer to bind onto the steel. Rustoleum has similar products - check their website.

You are not treating leather under the car (i.e. lanolin)- it's steel. Doesn't matter if the oil is made by an animal, a tree, or derived from petroleum. Your own body makes them too. A hydrocarbon is a hydrocarbon is a hydrocarbon.

The principles of chemistry are universally ubiquitous.

I lived in the rust belt. I lived through the gooing of car bottoms in the 70s. All it really did was piss of mechanics and smell up garages. In the 80s it was "new" oils and waxes. The chemistry has not changed since then. And I watched in the late 80s as Chevrolet, Cadillac, Ford, Dodge and Chrysler paid millions to settle "rust proofing" lawsuits.

Save yourself some money. Go down to a garage and ask them for their oil change barrel. Spray that under your car. It will do the same thing. But it's permeable. The salts find their way through and bond to the steel and catalyze the rusting process.
 
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nhmountainman

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Coat it. Keep that undercarriage looking nice and protected.
 

Fly by Nite

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Corroseal is a rust converter. It also can be applied on painted surfaces as it will etch the surface and function as a primer. It's designed to be topcoated afterwards.
I spent time on their website, there is no mention of it being a rust preventative.
It will not shed water or prevent rust from forming on untreated surfaces!

Lanolin is a naturally produced water shedding substance. It works on any material as long it retains adhesion to the surface. It doesn't dry and harden, therefor it will flow into say, a rock chip in the paint of the frame rail, so it has some self-healing properties.
There are many other products which work in a similar fashion but are petroleum based

Perhaps 'undercoating' isn't the best term to describe modern underbody treatments. Modern treatments work by wicking into joints/crevices, sealing the surfaces, and shedding and displacing water and moisture.

An example of old-school undercoating is Ziebart. They apply a thick coating designed to seal the surface. The problem is, the coating will fail in areas, allow moisture to creep in, and it will trap the moisture and the metal will rust. It's a one-time application.
https://www.ziebart.com/auto-care-services/undercoating/undercoating-services

An example of modern commercially-applied rustproofing is Krown.
It's petroleum-based, not Lanolin based, but works in much the same way.
It should be applied annually on the undercarriage.
There's a vid on their site here:
https://krown.com/en/passenger-vehicles/

'Repair Geek' on YouTube tests a variety of products.



And for @Doc TOC , a review of Corroseal:
[/QUOTE]
 
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