Undercoating, Rustproofing, etc

The undercoating that dealers push so hard has no value except to their pocketbooks. However is there a way to treat the underside of a truck or car to actual prevent corrosion from salt? I would hate to have to go through another disaster like my 00 Tacoma. The truck had no problems, the dealership something else.

The best thing to do is use a car wash in the winter…reduce any salt build up…

Yes, there are ways. Using base materials that don’t promote rust, designing the vehicles such that no pockets collect water and all areas ventilate well, noncorrosive coatings, bonding techniques and materials that don’t promote rust, and numerous other ways…and they have all been done by the manufacturer. There is nothing aftermarket that you can OR SHOULD do. Some rustproofing processes actually create breeches in the rust prevention technologies incorporated by the manufacturer and can promote rust.

Firmly say NO to the dealer. If they insist, walk out and go elsewhere.

Well stated advice so far. I managed a collision shop for a couple of years. I saw inside body panels to see how hit-or-miss “rust-proofing” was and saw how engineered drains designed into car bodies actually got plugged up with it.

Most car companies offer decent rust-through warranties. Added rust-proofing can actually void that warranty.

I live in the rust-belt where I drive in salt for 6 months. I pay attention to which car makes and model suffer most from corrosion and stay away from them.

Every car I’ve ever owned has died from rust before the mechanicals could die a natural death.

A guy just down the road (I live in the middle of nowhere) drives a stainless steel bodied, Back To The Future, DeLorean. It is stock, no Mr. Fusion!

There are less damaging snow/ice melters, but they cost more. One is a by-product of breweries. How great would that be to have the roads smell like Michelob without hurting your ride?

I, for one would be willing to pay more in taxes for the banning of salt. Sign me up!

Smart move on your part. Short of moving somewhere that does not have snow, I suggest two things. Try to get the salt washed off as soon as possible after it has been on the road and don’t garage you car during the salt season. As long as the snow remains as snow or ice, the salt is locked up and not harming anything. It is only when it warms up and starts thawing that the damage is done, so if it is very cold out, you will get less damage keeping that truck well below freezing.

Rustproofing DOES work…IF (BIG IF HERE) it’s applied correctly. That’s the caveat.

But with the way cars are made now…it’s really NOT needed. Living in NH we do get some snow…After 9-10 years and 300k miles our cars still showed no sign of rust. The only thing we’ve done is try to wash the vehicles once a week…especially the underside.

It sounds like my only alternative is to drive 50miles one way to a car wash once per week. I was hoping to avoid that! Toyotas recall of trucks is now fixed in that they won’t warranty corrosion due to salt. One of the Toyota mechancis told me that Toy frames harbor more crevices for salt so they rust out sooner. Sad it is

I agree (as I often do) with the advice from the regular posters. Washing off the vehicle is all that should be required of a reasonably new vehicle like yours; factory undercoating is installed with the intended market in mind. As a rule, the undercarriage is a pretty safe place to spray, but by experience, I caution you to be careful about high pressure direct spray on ABS sensors at the wheels; they don’t like it, and their wiring in particular becomes frayed over time and will be damaged by high pressure spraying.

Salt The Planet

It’s not the manufacturer’s fault, it’s that #%%@! salt!

People in places where they don’t dump it all over the roads don’t have a problem.


I would suggest that washing it at the car wash may not be a good as one might think.

First many car washes recycle water. So is you go in after someone with a lot of salt, or even a lot of your own salt, it will just move it around and maybe put it places it was not in to begin with.

Second the first puddle of salty water you splash though is going to replace the salt you just washed off. I really doubt if driving 50 miles to a car wash is going to be worth the cost and effort.

You are being mislead. Vehicles no longer come fully factory undercoated and there’s a good reason for it. Only about 15 States in the US actually use SALT on their roads in the winter. (Mainly Northeast & East Coast States).

Once upon a time, EVERY vehicle from Factory was coated…and you paid for it to. It was listed right on the Monroney Sticker! Customers living in the other 35 States in the US were literally being FORCED to pay for something they did NOT need. After a lot of media attention and the involvement of the Government, Factories stopped applying this to ALL vehicles.

If you live in the following states:
West Virginia
New Jersey
New Hampshire
New York

You SHOULD get undercoating. Most dealerships in these states offer it and it’s not very expensive. (Couple hundred dollars). The only exception to this would be if you are purchasing a Mercedes Benz or a BMW because they still undercoat all of their vehicles.

By the way, I have been a toyota mechanic for 18 years and I can tell you that the Corrosion Perforation Warranty does not cover undercarriage corrosion. It only covers Side Panel Body Rust that is large enough to poke a pen through!

As far as paint protection, I think Toyota actually recommends this to customers. Mainly because the Consumer Product Safety Commission banned Lead-based Paint from being used on Automobiles in the US meaning you car is now more likely to get permanent damage from UV Rays, or even something as simple a bird crap! NASCAR even puts a protective film on their race cars!!!

I hope this helps!!!

PS - I should also mention that WHO is applying your Undercoating & Rustproofing is equally important. At the dealershipI work at, we have to Toyota Certified Techs who apply it! I would be hesitant to recommend Undercoating & Rustproofing is it’s some Joe Blow hole in the wall shop up the street doing it for the dealership. If applied incorrectly, Undercoating & Rustproofing could cause the very issues they’re meant to prevent!!!