O'T. Truck under body rust, solutions?

5 axis Fidia guy · Jan 14, 2019

Hey guys, I suppose I will get a whole bunch of answers here but I will give it a shot. Living in WI and driving my truck thru salt and slush constantly, I can almost hear my truck rust when I park it in the garage for the night. Other than the obvious professional undercoating right off the showroom floor, has anyone had any luck stopping or at least slowing down rust that is already started? Such as POR15 or Chassis Saver type products.

gustafson · Jan 14, 2019

It is mostly what you buy, the design of vehicle contributes to the rust

remember the dodge Aspen?

permanently changed the way cars are made, or I should say the lawsuit did

Every car released in 1978 or after was much more rust resistant. Think the downsized square caddies

Problem is it is ten years before you know the answer.........

They put foam in the rear quarters which absorbs water and causes rot, but hey,they don't squeak

DDoug · Jan 14, 2019

Leetle bit late to start now.

Need to wash it very thoroughly in the spring (hit every puddle you can)
and in the summer go at it, removing all the dirt road mud.
Let dry in the hot days of july/august (stay out of the mud/dirt)

Apply Fluid Film, and some other "secret Sauce" recipes.

Lower down your mud flaps as much as you dare, add underbody plastic panels (see some of my other postings with pix) to keep the salt off of the body.

Miguels244 · Jan 14, 2019

Regular car washes including the under carriage spray.
There are plenty of light oils out there, using them with some regularity will help keep things from sticking.

BoxcarPete · Jan 14, 2019

If you want to go the route of underbody coatings, I would advise you to be cautious of using anything that includes petroleum-based oil or tar as a base. EPDM rubber is a common choice for vibration dampers and more importantly, coolant lines. The stuff works great at the temperatures and media it will see in normal operation, but it does not play nicely with petroleum oil. Volumetric swell, reduced hardness, and loss of tensile strength are common effects of oil exposure. Not that you'd intentionally coat all your coolant hoses with underbody spray, but an over-zealous applicator might overspray all over a fitting to one and move up your timetable for a rupture by a few years...

I might be overthinking it, but I've had a customer select material that is both more expensive and lower-performing overall because of that concern. It was a mounting isolator for a heavy truck suspension air valve.

cg285 · Jan 14, 2019

we've put them on the lift, pressure wash and when dry used a pump up sprayer with ospho

Miguels244 · Jan 14, 2019

BoxcarPete said:
If you want to go the route of underbody coatings, I would advise you to be cautious of using anything that includes petroleum-based oil or tar as a base. EPDM rubber is a common choice for vibration dampers and more importantly, coolant lines. The stuff works great at the temperatures and media it will see in normal operation, but it does not play nicely with petroleum oil. Volumetric swell, reduced hardness, and loss of tensile strength are common effects of oil exposure. Not that you'd intentionally coat all your coolant hoses with underbody spray, but an over-zealous applicator might overspray all over a fitting to one and move up your timetable for a rupture by a few years...

I might be overthinking it, but I've had a customer select material that is both more expensive and lower-performing overall because of that concern. It was a mounting isolator for a heavy truck suspension air valve.

This is a good point.
Chemistry, surface prep and physical placement all make a huge difference in the performance of any protective coating.
Just keep the machine clean and spray a light oil/wax coating on regularly.
Maybe with and oil change as needed.
If younote any spots Then consider a more agressive option.
If you don’t expect to own the vehicle for more than a decade don’t worry about it.

JST · Jan 14, 2019

Anything on the underbody of a vehicle should be expected to get oil or other petroleum product on it. That just happens.

Undercoating is the wrong answer.... it PROMOTES rust, the worst kind of rust. Traps water under it away from air, giving the black burrowing rust. You are probably better off with nothing in some ways. It's great if there is never a hole or defect in it, but once ther is, you have a rust hole coming.

Dissolving some heavy oil in mineral spirits allows you to spray it on the rust areas, which generally will stop surface type rust, but may not stop the black rust that burrows right through. I have heard of adding vaseline to the mix as well, to make it more resistant to being washed off.

You have to do that on a hot dry day, after several of the same, so that you are not trapping moisture.

Another good thing is to use any thaw time in winter to wash off the underside. I have laid out a hose, with a rotary type lawn sprinkler on it, turn on the water, and pull it a foot or so at a time from back to front under the vehicle. Seems to do a good job, especially if you then spray the wheel wells also.

m-lud · Jan 14, 2019

There are inner and outer body panels in fenders,rocker panels and rear quarter panels. There are small slotted drain holes at the bottom where they meet. Flush them once or twice a year and make sure they are clear of blockage. They are built in mud traps if not kept clean.
I agree that asfault base coatings are wrong. They end up holding moisture.
The humidity in your part of the we world has an effect. High humidity doesn't let mud and road dirt dry out as fast. Gravel limstone road driving requires more diligence.
I agree with the light oil or fluid film,mineral spirits type treatment would work best. I think the dodge Aspen was the car that the top of the front fenders rusted away.
It's the built in dirt traps that cause the most problem. Areas that are hard to treat with anything.

Demon69 · Jan 14, 2019

Id go with get it on ramp and jet wash it out, Use a needle gun to knock off any thick scale, coat inside any box sections and outer floor pans inner flitches etc with with liquid waxoil type products that dont through harden, and stay semi liquid.
You might be better off paying someone, its a shite job!

Ziggy2 · Jan 14, 2019

JST said:
Anything on the underbody of a vehicle should be expected to get oil or other petroleum product on it. That just happens.

Undercoating is the wrong answer.... it PROMOTES rust, the worst kind of rust. Traps water under it away from air, giving the black burrowing rust. You are probably better off with nothing in some ways. It's great if there is never a hole or defect in it, but once ther is, you have a rust hole coming.

Dissolving some heavy oil in mineral spirits allows you to spray it on the rust areas, which generally will stop surface type rust, but may not stop the black rust that burrows right through. I have heard of adding vaseline to the mix as well, to make it more resistant to being washed off.

You have to do that on a hot dry day, after several of the same, so that you are not trapping moisture.

Another good thing is to use any thaw time in winter to wash off the underside. I have laid out a hose, with a rotary type lawn sprinkler on it, turn on the water, and pull it a foot or so at a time from back to front under the vehicle. Seems to do a good job, especially if you then spray the wheel wells also.

We had a neighbor that had a truck that was rust proofed by a famous after market vendor. 6 months after buying the truck, the right front fender was smashed in by a person at a stop light. New fender was not rust proofed. 5yrs. later the drivers side fender which was rust proofed was quite literally flapping in the wind. The other side, though not rust proofed only had a slight amount of surface rust which was acceptable.

Most of us took note on the issues that the aftermarket rust proofing actually causes.

Of course now, the manufacturers have gotten much smarter and are using layers of chemical coatings to galvanically protect the metal.

Ken hosford · Jan 14, 2019

I struggled with the salt issue living in Michigan in the heart off the rust belt. My thoughts are either spray with chain lube which has a high capillary action. chain lube is meant to penetrate and leave a oily wax behind when solvent evaporates .
Or I would paint it with an generic oil base paint with Penatrol added It makes paint penetrate .
The reason for penetration is all the spot welded seems are prone to capillary action with salt water you
My 96 F150 factory under coating on the frame chipped and pealed trapping salt water
A dozen cans were used on my truck .

DDoug · Jan 14, 2019

To all the suggestions of "oil" and "Grease products" ....Do you like
working on a dirt & grease covered POS ?

Because that's what you get....BTDT Several times.

ewlsey · Jan 14, 2019

I've seen smart folk recommend Krown. I believe it is a type of heavy wax. They actually drill small holes in the rocker panels and other areas (out of sight of course) and hose them down from the inside.

I would not use a rubberized spray one undercoating. That stuff is fine until it starts to rust, which it will eventually. Then the rust gets trapped behind the coating and it's game over.

AHS · Jan 14, 2019

As several have mentioned, salt is a big problem for vehicles. But let me give you another. This is 3rd party info, but the sources are very creditable in my opinion. Ok, the spray that is put on the roads to prevent icing, before snow, apparently will really do the job on metal and is worse than salt. I've been told that rinsing may accelerate the action. The only effect removal is with soap and water.

gmach10 · Jan 14, 2019

I hear you loud and clear. Proud owner of a 2003 Chevy Tahoe, almost KILLED a car load of teenagers who pulled out of a parking lot without looking. I hit the brakes and the pedal went to the floor. Funny how slow time moves when you're doing 35 and on the verge of T-Boning a Nissan. Brake line burst, gee guys maybe Garbage Motors aka GM should use Stainless Steel brake lines for safety sake. Just changed out the fuel lines on my daughters 2009 Chevy Cobalt, yep they rotted out too. Just saying!

ewlsey · Jan 14, 2019

I used to work on a lot of juice brake grain trucks. We pretty much quoted new brake lines any time a caliper or wheel cylinder had to come off.

john.k · Jan 14, 2019

I remember a movie once about Ford.....director was fired for making a safety mod that cost a few cents.......a few cents by a million cars .........I see salt water issues with boat trailers,some costing 15K.......even hot dip gal is only temporary cure.................commercial boat users spray with waste oil after fresh water pressure washing,and compressed air dry.

SBAER · Jan 14, 2019

Oil spraying works if done right, I don't trust others to do a good job because no one ever looks under the car to see if it was done right so the guy getting payed $12 an hour doesn't have a lot of incentive to hit all the nooks and crannies. I use a product called Corrosion Free, they sell a pretty good application system as well.

Corrosion Free HEAD OFFICE Contact us to Order

It surprises me that lots of people spend $40 000 on a truck and don't bother to oil spray them.

john.k · Jan 14, 2019

Actually,oil spraying works even if done wrong...but it makes a mess,and can always be spotted from a distance ......but cant be beat for cost and effectiveness........I know it works ,and so do many others ......

O'T. Truck under body rust, solutions?

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