Many years back when I lived at the coast I installed these so-called electronic rust-preventers in my vehicles - but I noticed they rusted anyway. So I emailed the chemistry professor of the local University and asked him how they work. Answer: "You have been duped - for the sacrificial anode to work, the vehicle has to be immersed in water!".
Hello,
This is correct. Some thoughts on this matter from both background and experience. Please bear with me. All the errors are mine.
Corrosion is predictable and preys on iron's tendency to return to its natural state as iron oxide. Set up the right environment, add oxygen and there you go.
The device above looks like a variant of cathode protection, which basically relies on DC to prevent the conversion from iron to iron oxide by supplying additional energy (in the form of electricity) to the oxidation reaction, in order to prevent it from happening. Iron loses electrons (in the form of current) to oxygen when it oxidizes, and a constant supply will keep oxygen from reacting. This idea works well for tanks and pipelines, which are in contact with corrosive stuff, but is only a complement to surface protection; any exposed iron surface will attract oxygen to form oxide, losing current in the process and extending corrosion.
A Cruiser is neither a pipeline nor a tank. Or a submarine, for that matter.
Sacrificial anodes, usually made of zinc, work to certain extent provided there is good contact between them and the iron to be protected. This technique just displaces corrosion from iron to zinc, and requires periodic anode replacement. Again, if there is not enough zinc an there is exposed iron, the former will be useless to protect the latter; iron oxidizes far more easily than zinc does.
The above leaves surface protection as the basic prevention method. A physical barrier between iron and oxygen is an effective way to prevent corrosion. It is better if that barrier is an organic liquid such as oil, because corrosion needs an acqueous media; oil and water do not mix, and that is why oil is so effective.
Auto makers add zinc compounds to primer paint to prevent corrosion, but we all know the hard way this is not enough. Paint eventually strips from the surface, exposing the underlying iron to oxygen. And ever since Henry Ford tackled the Model T's axle problem in the 1920s, no maker is interested seriously in building cars that last forever, but that is another story.
It is possible to apply DC or connect a sacrificial anode, but nothing is as simple and effective as surface protection, be it a lining or repeated oil application. Furthermore, DC and zinc rely on evenly protected surfaces to work.
As for me, I rely on a dry garage, a monthly chassis wash to remove any dirt/salts that attract water (and oxygen) and frequent (at least every two weeks) oiling. My recipe is a combination of WD-40, grease and lube oil, and has served me well. Oil needs something to help it stick to surfaces, like WD-40's alcohols or grase's organic salts. Oil alone will eventually drip unless there is a bonding substance.
Like maintenance, severe conditions require shorter application intervals. And once all surfaces are protected, DC or an anode can work as a complimentary measure.
My two cents.
JuanJ
