Does radiant heat in garage floors accelerate the rusting process?

Dear Car Talk

Dear Car Talk | Aug 01, 2002

Dear Tom and Ray:

I live in Vermont, where we get lots of ice and snow in the winter, and roads get a lot of salt spread on them. At any given time during the winter, a person's car might be encrusted underneath with 2 to 3 inches of a dirty, salt-laden, icy mush. I have heard that parking such an encrusted vehicle in a heated garage causes the icy mush to turn into a warm, salty liquid and that this accelerates the inevitable rusting process. I am an architect, and I've had several clients request radiant heating slabs for their garages. Is this is a good thing or a bad thing, with respect to rust? -- John

RAY: It's good for the rust -- i.e., bad for the car -- John. What you've heard is exactly correct. When the salty ice melts, it accelerates the chemical reaction that eventually turns a car into something my brother might drive.

TOM: Generally speaking, chemical reactions slow down as temperatures drop. That's why your battery doesn't work as well when it's 5 below zero. So by letting that salty ice stay frozen, you are, in effect, suspending the rusting process until such a time as you can clean the car.

RAY: On the other hand, rust is not everybody's foremost concern. These people want heated garages so they can get in an unfrozen car in the morning and have heat blowing on their tootsies before they spend 10 miles shivering. And maybe that's more important to them than keeping a car from rusting forever.

TOM: And if they can afford to heat their garage, maybe they plan to get rid of their cars after four or five years -- before rust is an issue, anyway.

RAY: Here's my suggestion: Since you're obviously dealing with high-end clients here -- and since you probably get paid a percentage of the construction costs -- you should use this as an up-sell opportunity, John.

TOM: Tell them you can't recommend a heated garage in Vermont because of the rust issue. So if they do want a heated garage, they also have to install the built-in, under-floor, high-powered car-wash jets that spray off the salt each night. Tell them it's sort of a "car bidet," if you will.

RAY: And then, if you're really on a roll, you can go all the way and try to sell them the hot-carnuba-wax dispenser!

Get the Car Talk Newsletter

Got a question about your car?

Ask Someone Who Owns One