Salt Corrosion: Undercarriage, Paint

I recently bought a Yaris to transport me around the midwest, and I'm worried about the effects of salt on the undercarriage. I've heard that Lexuses have no problem, but the Yaris is a budget car and probably made of cheaper stuff.

Do I have to worry?

If so, can you recommend a treatment?

I've heard of TC-11 and Pittman VaporWax 360ID and bunch of other stuff and I would love to know if any of them are any good.

How long are you going to keep the car?

If its leased and goes back in 3 years, do not bother. The factory rust protection will be fine. But if you are keeping it 'till it dies, then a proper, professional rustproofing job is worthwhile.

Usually this consists of spraying a heavy grease all over the underside of the car, so it gets in all the nooks and crannies, and also inside the structure of the chassis, hood and trunk. A good shop will also drill a few holes so the goo can get into inaccessable places, like the insides of doors and fenderwells. These holes are plugged with plastic plugs afterwards.

Around here (Toronto) this costs about $100 to $125, and is usually repeated every year, or every other year, to maintain the protection.

The heavy grease goo is better then the waxes and the asphalt material The latter two can dry-up, crack and allow water to penetrate, causing rust.

The 2 products you mention are not at all what you need. TC-11 is intended to free-up rusty parts, and Pittmans is actually a paint treatment

It used to be a lease car, actually. It's a 2008 that I bought certified pre-owned in NJ.

Is there any problem getting it rust-proofed at this age? Or once winter has started?

I have used the 3M Professional Undercarriage Coating on a few cars and trucks and it does a good job of protecting the underbody and helps with soundproofing. It is a rubber-based coating that is sprayed on.
For best results with any rustproofing job on a non-new car, first inspect the undercarriage closely for any rust formation and take care of it by sanding, wire brush, and top it with some rust converter. Then a shot of primer. If you don't think you will be undercoating for a while, then I'd highly recommend spraying the repaired areas with ColorPlace Rust Control spray paint which you can find at WalMart. It comes in black or white, but I usually use black. I treat all of my brake rotors and drums with it, and you can even shoot it onto areas of the undercarriage that don't have any OEM undercoating before you apply your own for even more protection.

Before you start this part, read the can to see at what temperature it should be applied at and check the forecast to time it right to spray on a warm enough day. Take a car-wash brush and give the underside a scrubdown and rinse or run the car through a commercial car wash with the undercarriage spraydown and let dry in the sun.

You'll probably need 4-5 cans of rubber undercoating. Mask off areas you don't want oversprayed such as the metal lips inside the fenders, door sills, plastic trim, etc. Spray it up into the wheel wells, around the struts, the control arms (but not the axles), the rear wheel suspension linkage. Avoid spraying onto the exhaust system. Wait the amount of time between coats on the can and then shoot it again. You're done!

Hope this helps!