by Glen Konorowski

Once upon a time, anyone who took good care of their car or truck would make sure to rustproof it right after purchase.

Times have changed, though, and today’s vehicles are much less prone to rust than their predecessors.

But this doesn’t mean that rustproofing your vehicle shouldn’t be done.

On the contrary, it’s still the best way to protect your car from rust.

Cars are still subjected to rapid temperature changes – driving into a warmed-up garage in the dead of winter, for example – that can cause condensation to form on the inner panels, which in turn can, over time, lead to rust, since those enclosed panels can’t drain.

Winter highway driving doesn’t help, either, as salt from roads can get into hard-to-wash areas and cause rust to form. Same goes for cars in coastal areas with lots of salty sea air.

Generally, there are three types of rustproofing: the used-oil spray people applied to the bottom of theirr car many years ago; the thick tar-type sprays used years later; and the modern chemical/oil-type sprays used today.

Rustproofing: then
The first form of rustproofing involved spraying used oil from oil changes under your vehicle. When cars and light trucks didn’t have inner fenders and metal was prone to rot, this was considered the best way to keep rust from forming early in a vehicle’s life.

Done yearly, this could hold off rust for a good while, depending on your driving habits; at the same time, it was really messy, and not really good for the environment.

In the late 1950s, a newer, thicker tar-like coating replaced oil, since it was less susceptible to being scraped off on gravel roads or washed off in winter and wet conditions.

For the first few years this method worked well, but over time the tar would dry, allowing water to get trapped in the gaps under it, only helping the oxidation process and causing more rust. Some new car dealers still sell this kind of rustproofing.  

Rustproofing: now
Today’s rustproofing offers the best of both these processes, plus a lot more. Like the oil spray, newer rustproofing sprays are more liquid than thick, gooey tar, letting it get into all of the car's nooks and crannies. But like tar, they’re sticky, to adhere to the smooth underside of modern vehicles.

Unlike oil, it won’t come off in the wet, though the chemicals in the spray formula allow it to flow into tiny places just like water. If moisture finds its way into these tight places, it will evaporate before it ever penetrates the rustproofing to the bare metal.

Today’s professional rustproofers use special tools and a few drilled holes to get into all the inner body parts of your car, allowing the rustproofing to get into areas never accessible before. Most will guarantee your vehicle will never rust from the inside out—as long as you keep it sprayed every year, of course.

Getting your car rustproofed is something that should still be done just after purchase for the best anti-rust guarantee, even if it’s new. Rustproofing can be applied any time of the year, though beware your car will be most susceptible to rust during the winter.

Think it over — this could be your last chance before the season starts.