Electronic Rust Prevention Units- Which One ??

And what do you base that on Eric.....some substance to your statement would be good.

For the record I don't own one.

Cram.
The idea of sacroficual electrodes protecting metal was developed for the marine environment where you have an electrolyte to carry the current and the metal to protect the structure. In a vehicle you don't have or want salt water to carry the current so it can not work.
Eric

Ok, thanks for that you have now given me something to research and ponder. The basis of what makes this forum so good.

Actually, some devices claim to radiate an electron field out from pads, which is supposed to prevent rust from forming. Only thing is the electron field cannot penetrate fully enclosed areas like rocker panels (where you can get rust). Faraday, back in the 19th century, proved the principle; called a Faraday cage. Don't think anyone has disproved it since. I suppose you could cut holes in your rocker panels and put the pads inside.
Sacrificial anodes are also used in the ground to prevent underground tanks from rusting, but again, they rely on damp soil to allow a current flow. Not much use in a vehicle unless you use accumulated mud to allow current flow.
Like DID, I've had no rust problems with my earlier Maverick and my current Patrol, and I've done absolutely nothing to the vehicles. Most modern vehicles are well primed for rust prevention.
On an old Fiat I had (rust came as standard equipment), I used fish oil, which seemed to stop the rust in its tracks.
Gerry

Owen, you said "any one who has studied a bit of electrical theory would tell you that rust is caused by electric current between disimilar metals across an electroyte."

Which begs the question why a piece of black steel left lying out in my back yard all by its own (no other metal near it) started rusting??

Me thinks there is more than one way for steel to get rusty.

From the book by R.M.E. Diamant
The rusting of steel plate
The question now arises : Why does a piece of steel plate which is left out in a damp atmosphere start to corrode? Where are the anode and cathode now?
The answer is that steel is not a uniform metal like gold. It is, in fact, a conglomeration of a lot of crystals with quite different compositions. There is some pure iron, and there are crystals of a material called cementite which is really a compound of iron and carbon. There are crystals of a material called martensite which is a solid solution of carbon in iron, and finally there are even specks of carbon particles, which are very cathodic indeed and therefore readily act in this way in the corrosion cells so formed. After all the cathode of a torch battery is always carbon too. Admittedly all these crystals are tiny, and can normally only be seen with a microscope. But the different forms of iron and iron/carbon compounds form lots of tiny corrosion cells, each complete with its own anode and cathode.
But things can be made a good deal worse if parts of the steel plate are obscured. The trouble is then that the parts where the air can easily get to the surface become cathodes, thereby making all other parts into ready anodes. In other words the differences between the sections on the steel plate become accentuated and corrosion takes place in the form of deep pits.
That is what happens if one gets a deep scratch on a painted panel of a motor car. The steel which is exposed to air becomes the cathode, and immediately the part next to it starts rusting. This is the part of the steel which is just covered by the paint film. This lifts off the paint film and gets a bigger cathode. The rust then spreads deeper and deeper underneath the paint film, and soon the corrosion damage caused is far greater than would have happened if there had not been any paint on the steel in the first place.
An imperfect paint film is far worse from the point of view of corrosion than no paint film at all.
If one covers a large iron or steel article with a coherent coating, be it paint, varnish, enamel or plastic, one must always avoid any imperfection. If even a pinhole is left, where the paint does not cover the base metal adequately, then at this position rusting occurs at a particularly rapid rate. Because all the corrosion is concentrated there, the rust goes really deep. This, for obvious reasons, is often referred to as the "Achilles heel" effect.
Rust always affects little unprotected aieas particularly badly. For example, if you should have an argument with a gatepost while in your car, and the scratch penetrates the paint film and protective phosphate or chromate coating, then you will get very rapid corrosion taking place unless you set to almost immediately and patch up the scratch. Underbody corrosion is always particularly harmful at tiny unprotected spots, particularly if they are hidden from the atmosphere. All crevices, joints and the like are liable to rapid attack and should be specially protected.
One of the worst forms of pinhole attack is that which takes place on plated steel surfaces such as car bumpers. Commercial chromium plating contains copper, nickel and a minutely thin film of chromium. Two of these metals, namely the copper and the nickel, are strongly cathodic to the steel from which the bumper is made, while the third, the chromium, although theoretically somewhat anodic to the iron, is in practice also cathodic. It can be seen therefore that if there should be even a tiny pinhole in the chromium plating, one is immediately in trouble. One then has a classic example of a minute anode"
Unquote
Hope this explains
Owen

Thanks for that Owen, an interesting read. My 20 yo troopie knows all about the "pinhole effect" and, unfortunately, shows it too.
Klaus

"I put one in a VS Commondoor and still had rust in less than 12 months. "

Serves you right.
But we are talking about motorcars here. 8D

Shifted to a Ford when I sold the Commodore still didnt work.

So now what bright comment have you got

Havent put it in the Cruiser as perhaps you may consider it a real car.

Same rubbish with a different badge :D

& there's no need to get prickly, I was just joking :)