Say no to rustproofing

Dear Car Talk: I recently purchased a certified used 2015 Toyota Corolla. The dealer recommended that I purchase rustproofing. He said extra rust protection is no longer done by manufacturers, since cars are sold in various climates. I had rustproofing done on my previous 1999 Corolla when it was new, yet the sides still rusted in the past few years. I held off on the rustproofing, and am seeking more information about how these recent models are made and what difference this might make, especially since the car has already been driven for 15 months. Your thoughts? Thanks! — Barb

Skip it. And they wonder why people still don’t trust car salesmen. That stuff about different climates is complete claptrap, Barb.

The entire rustproofing industry has largely disappeared, because car buyers really have no need for it anymore. Nowadays, the aging rustproofers just get together once a year in Las Vegas and reminisce over pictures of old honeycombed Fiats and Datsuns.

In the past few decades, carmakers have gotten a lot better at slowing down the rusting process. Typically these days, during manufacturing, the metal car bodies are subject to a process known as “E.D.” No, not that E.D. — electro deconditioning.

During E.D., the steel car body is cleaned, coated, then dipped in a chemical bath while electrical voltage is applied, and then baked. All that happens before it gets paint and a clear coat. Manufacturers also do a better job of sealing up places between the parts where water can get in and start the corrosion process.

So all that effort has done a pretty good job of delaying the onset of rust. Of course, if you keep your car for two decades and live where the roads are salted, all bets are off. Nothing can prevent the chemical reaction that creates rust forever. But gone are the days when your Chevy Vega started to rust in the showroom.

Even before all this stuff was incorporated into the manufacturing process, aftermarket rustproofing was of questionable value, if only because it wasn’t always done well. Installers would make holes in the car and spray rustproofing into the insides of the doors, for example. But the holes themselves sometimes allowed water to get in and rust to form.

So, your new-ish Corolla is already rustproofed, Barb — or at least rust-inhibited. And there’s no reason, anymore, to pay extra for additional rustproofing. It’s unlikely to help, and it could even hurt.