No, they don't work. At all. I mention them in passing in this column, as being even less plausible than the electronic rust inhibitor doodad I'm complaining about there.

See also this page.

(The Car Talk guys don't know why these gadgets don't work (they have sacrificial-anode devices mixed up with electronic ones, and don't know that sacrificial-anode devices work because the thing they're protecting is immersed in an electrolyte, which cars aren't), but they do at least know that they don't.)

The Defense Pak Blah Blah, of course, does not explicitly claim that it's a cathodic or impressed current system - nooooo, it "sends a continuous stream of silent electronic pulses throughout the body of the vehicle", which "act to inhibit the electro-chemical process".

Except, of course, they don't. This is pseudoscientific gibberish. A conductor with current flowing through it will rust just like an identical piece of metal that's just sitting there, unless it's part of a natural or forced electrochemical cell that shifts the corrosion somewhere else. Cathodic and impressed current rust protection does actually work, when it's used on something that's surrounded by a conductive medium like water or earth. It just doesn't work on cars that're (mostly) surrounded by (mostly) insulative air.

The process the Defense Pak and most other "electronic" anti-rust gadgets claim to use is even further from usefulness. It is nonsense, and cannot work, ever.

I, of course, am not qualified to tell the universe what to do. Neither are all of the world's electrochemists and physicists. The proof is in the pudding; if your explanation for your antigravity machine is nonsense but the thing's obviously hanging there in the air, you still get your Nobel Prize.

But these products fit a well-established pattern which makes clear to me that if they're not scams, they're doing a very good job of pretending to be.

Umpteen companies have been selling electronic rust stoppers for many years. Many billion-dollar industries would love it if the devices worked. And yet the devices are still being sold one by one to regular Joes.

If electronic rust preventers actually worked, the people who sold them would have made more money than God in a week and retired, and most if not all vehicles would come with one built in.

Does Caterpillar include an electronic de-ruster on every bulldozer? Does the US Army put 'em on their vehicles?

Kenworth?

Toyota?

Bueller? Bueller?

Note that you certainly can use a sacrificial-anode or impressed-current system on any part of a land vehicle where water tends to accumulate - if there's some nook or cranny that always gets damp and starts rusting, you can bolt a lump of magnesium in there and protect that particular spot just fine. Or, better yet, you can give the whole car's steel panels a coating of a suitable other metal like, oh, I don't know, zinc.

This process is, of course, known as "galvanising", and it's normal in the car industry these days. I don't think it's even possible to buy a steel car that doesn't have galvanised panels, any more (though there are still plenty of cars that aren't fully galvanised). I think there used to be problems with spot welding such panels, or something, and that was one of the leading reasons why old cars rusted so rapidly and so badly - they had to be made out of ungalvanised steel, or the galvanising was damaged by the welding and they rusted at the welds, which is of course the very last place you want rust to start. But modern mainstream cars are well-galvanised from bumper to bumper.

Modern cars are far more rust resistant than older cars, mainly because of galvanising but also because of the wider use of plastic for some panels and bumpers, and possibly also because of better paint. People who remember how fast their old Cortina was eaten by the rust bugs may, therefore, buy a new Corolla, pay extra for some shady dealer to bolt a useless electro-gizmo onto it (or, more traditionally, pay for greatly overpriced "undercoating" to be sprayed all over the car's belly - though at least that stuff probably does genuinely provide some protection), and be amazed to see that there's no rust to speak of after ten years.

Except that that's normal these days, if you don't live by the seaside, drive on salted roads in some cold-country winter, or keep scraping your car on concrete pillars in the supermarket parking lot and exposing bare metal.

Oh well. I suppose it's nice, at least, to see a non-functional automotive gadget that's not supposed to do anything to your fuel economy.