kalieaire

Hey everybody, I got bored and I just felt like sharing this info with you guys.


I'm sure a lot of you have heard about those electrical units that pump electricity through your chassis to resist rust.

You think it's BS.

You know what? you're WRONG.

I've read a couple of other posts that people have put on here, even some people who claimed to be well versed in "corrosion electrochemistry" have spoken against this electrical form of rust protection. Other people however have correctly termed this form of rust protection as "Cathodic Protection".

Here's more information from a post I wrote on rx7club.com just recently.



If you want to use an electronic device to prevent rust? yeah, you can do it. How do I know? Well there's a website called google that helps you find out everything. (find out how rust works at http://www.howstuffworks.com)

Anyway, How does rust work? If you know chemistry, you know the answer, but if you don't here's a primer:

Iron oxide, that reddish/orange substance commonly found on pieces of iron, steel, that are unprotected by any sort of coating, even on old cars, also known as rust.

Iron oxide is basically Fe2O3, two atoms of iron connected to three of oxygen.

Oxygen in the air leaches, with an electrolyte(water), electrons from normal iron to form rust.

This sort of electrochemical reaction is one defined with which iron, being the sacrificial anode leaks electrons to create rust.

There's a way to prevent the electrons from leaving your iron. Here's how:

You can run a current through the entire chassis of your car, some units use 12 volts, some step it up to 40 volts. However, this isn't quite necessary since oxidation of anything takes a certain amount of time and isn't completely immediate, it all depends on the conditions of the air and the amount of moisture present to supply a good electrolyte.

Another method would be to grab a piece of aluminum, or magnesium, or even zinc (ship builders, civil engineers, and people use this on ships, piers, manholes, water towers, hot water heaters, among other things, to prevent corrosion) and bolt it down on your unibody someplace inconspicuous. However, you'd have to make sure that the magnesium has electrical continuity to your chassis, otherwise it's useless.

The iron in your car will leach electrons from the magnesium block, or whatever metal you choose as your sacrificial anode, and distribute the electrons into the air without causing rust.

Slowly your magnesium block will degrade, but your car will be perfect for hundreds of years!

Most likely, depending on how much salt and humid weather your car is exposed to, a sacrificial anode of a pound could last two to four years.


How much does a piece of magnesium cost? about 20 bux a pound.

----Electric rust prevention systems do work, but they depend on your battery, some have autoshutoff systems that won't drain all the electricity from your battery, but for me who frequently garages his car, I would rather grab a piece of magnesium for 20 bux every couple of years.

Rotary Nut

No BS but the Navy uses this technique on all their subs. They use
Sacrificial anodes to protect the hulls of ships and subs.They react with the surrounding sea water to prevent the hull form coroding.


Also sheck this one out !

Doctorr

The sacrificial anode HAS to be in the same electrolyte as the steel that is being protected.

Otherwise, Mazda could just bolt a 5 cent plate of magnesium inside the trunk, and protect the car forever.I wouldn't listen to people who say "I do it, it's just in my glovebox, and my car is rust free!" Think about the physics of it....

To protect a wheel well from corrosion, the anode would need to be outside, in the salty water. The heavy corrosion it suffers (that IS the point) would also attack the electrical connection to the steel, and when the bond is gone the protection is gone. Also the corrosion tends to form a protective crust on the anode, which either has to be frequently scraped off, or it will stop the process.

Just about all outboards have an anode, but it is always BELOW the waterline, and of course, on the outside.
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doc

Thread from March, same subject....

FirstSpin

You can't run current through your car of any sort unless you provide a place for that current to go. A car that's insulated from the ground by rubber tires won't conduct electricity. If you did have current flow, you'd basically have a dead short and would soon deplete any conventional portable dc current source.

The cathodic protection systems with which I'm familiar are for buried metal (pipelines). There they have to induce current flow from the cathode (the pipe) to the anode (the magnesium rod). Both the pipe and the anode are buried in the ground and the current travels from one to the other by means of a conductive metal (copper?).

The corrosion basics presented in the first post above are correct but they apply to corrosion of metals submerged in or surrounded by an electrolyte solution. I'm not at all sure that you can "plug these principles in" (pun intended) to systems where the electolytic link between cathode and anode is spurious or intermittent.....