Electronic Rust Control - Does This Work?

Factual Questions
1

I work at a company that manufactures these devices. We have multiple test reports that show that they work in a controlled situation. We do both traditional spray on and electronic rust proofing and have much better results with the electronic. It seems to me that these things work, but I still have my doubts. I know they work on bridges and boats but do they really work on vehicles?

The reason I’m asking is we occasionally get cars coming in that it doesn’t seem like it worked at all, but then other older cars don’t have a spot of rust.

Does this concept of rust control on vehicles make any sense?

desulting

BTW: This is my first post, but I’ve been here for years. I remember when the board went subscription. Thanks to you all for fighting my ignorance all these years.

2

I’m guessing the device is supposed to be a cathodic protection system. They work by lowering the electrical potential of a metal (almost always steel) with respect to the water it’s exposed to, which reduces its corrosion rate.

Cathodic protection systems are of two types. One type uses “sacrificial anodes” of zinc or aluminium alloy, bolted to the structure to be protected. The current arises from galvanic action and the anode corrodes away over time. The other kind uses “impressed current”, where the anode is either scrap or else noble, and the current is provided by a DC power source.

For cathodic protection to work, there has to be a current flowing out of the anode, through the water, and into the metal to be protected. Only metal that is contact with the water, said water also being in contact with the anode, will be protected.

Which is a long way of saying that the device won’t prevent a car from rusting in the rain, but it might help if the car was at the bottom of a lake! Unless your anode is a fine mesh that covers the whole car…

3

“controlled situation” is the key I’d say.

All the electrical current in a boat to operate the various systems are isolated from the boat itself. Occasionally in a marina you might have a “hot boat” which can wreak havoc on nearby underprotected boats. These boats allow current leakage through poor wiring.

However most cars utilize the entire metal of the frame and body to conduct the current of their operating systems back to the battery. I can’t see how you can control corrosion electrically with these cars.