Can a block of 99% pure Zinc help prevent rust?

This is quite an interesting idea if it proves to be valid. One of the moderators on a car BBS I frequent has installed a 1"x1"x1/2" block of 99% pure Zinc to the undercarriage of his vehicle saying that this can aid in corrosion prevention. Sounds a little out there but I'm no mineral expert either. The idea has been used by the RAAF to prevent corrosion on aircraft and is apparently quite successful. Anyway, surely someone on XOC has at least a high school education, or perhaps a GED and can shed some light on this Zinc theory for me.

*Nope my X is fine, the only rust I have found is exhaust related parts for the most part, but I'd also like to pursue this if it works to keep it that way.

an "anode" or "annode" i think is what we used to call them, never heard of any commerical or civilan use thou...

Sounds a little strange after I did some research today but have placed an inquiry with the International Zinc Association (yes its real) to get some more insight.

That's similar to what they do in hot water heaters. Not sure exactly how it works though.
I'm wondering if it would still work with all the current running through the chassis on the way back to the battery ground.

This is always done on boats to prevent corrosion to metal parts. The idea is that you use a more reactive metal in the "block". The ions that cause corrosion will travel to the more reactive metal and corrode that rather than the metal you are trying to protect.

Some of them (such as on huge military and/or transport ships) can weigh tons.

Commercial Marine Anodes "Zincs"

Not sure how sound the principle is when applied to cars, though: Cathodic Protection for Cars
Here is an explanation of Galvanic Corrosion:
Galvanic Corrosion

And magnesium would be even better. It was debated about a year ago and I was reminded that the theory works in a closed system...like a ship (they use magnesium ingots on navy ships as a sacrifical anode). Not much help for an Xterra.

Be careful with pure magnesium...get it hot (with a flame, etc.) and it will burn a hole in just about anything. I think its autoignition temperature is around 473 degrees. Also, when you get it wet, it evolves hydrogen gas (very explosive).

I just keep the ashtray and cupholders full of pennies, they are 97.5% Zn! Works Great!

Pennies in the ashtray, that was good. I'll give you a special smilie. Seriously, this might work. The only problem is that to be effective you need to have a "current" or circuit, something that can carry the stuff through the entirety of the vehicle. Maybe the static electricity created as you drive can serve such a purpose.


[ 12-31-2001: Message edited by: LastRites ]

Some guy near me has a solar=powered thing on his truck that is hooked to the frame and supposedly runs a trickle charge through it constantly to inhibit rust. Sounds like a similar idea. I always wondered if it worked or was snake oil.

The whole thing smells to me.

You guys try it and get back to me 10 years down the line. If I'm the only one who is rusted then so be it.

Try out some Z-Max while you're at it.

For those in Canada and Washington go to Trail and take a tour of the Zinc factory. At the end they will give you a bunch of pucks of zinc they have left over. Great stuff and should be about the right size.

When I lived in Corvallis we used zinc wire on the ridge of our roof so that we didn't have to mow it come spring. The stuff kills all that thick green moss. The zinc worked by leeching into the rain water. I guess in that regard if you are haveing moss problems with the X zinc will at least help there.

Guess that answers that.

Seemed a bit hokey... when you think about it rust is a reaction of iron with water; now how would the zink prevent this reaction if the iron/steel is 3 feet away? Elementary, my dear Watson, it can't.

Alright, as a chemist, I can't stand this anymore.

Iron corrodes by becoming the anode of an electrochemical cell. However if we connect the iron to a more easily oxidized metal such as zinc or Mg,, then this metal becomes the anode of a cell and it corrodes rather than the iron. The iron becomes the cathode at which oxygen is reduced to water.

For example, if a Mg or Zn rod is connected to an underground tank or steel pipe, then the Mg or Zn is oxidized instead of the pipe. The more easily oxidized metal is called a sacrificial anode.

Above paraphrased from "Chemistry" - Gillespie, Humphreys, Baird and Robinson. Page 620.

So, It doesn't matter if it thirty feet away or three, as long as there is path for electricity to follow - it works. Like someone else said - we've been using this on boats for years. I know my boat has Zn sacrificial anodes.

If you want, I can give a somewhat quick explanation of standard reduction potentials.

TimR

And this is why it doesn't work on cars, air isn't a good conductor, boats have water to complete the circuit, bridges have the moist riverbed.

Zinc anodes do work, just not on cars.

"aahhgkagkagkagka...aahhgkagkagkagka...Oh me garshk!!...That's all I can stands and I can't stands no more!!"

Sorry Tim I couldn't resist. BTW the IZCC (Internet Z Car Club) had this debate a while back. What I got out of it was I either had to float it [salt water is ideal (salinity?)] or sink it (saturated in the ground) in order to promote said resistance to corrode (my Z cars already understood this). All in all I now know it won't work on my vehicles.

Just to throw another comment into the mix...

A friend of mine has a 2000 Blazer and it is loaded (every option). One thing that it has under the hood is a few circuits that run from the battery to the chassis/frame and various body panels and emits a constant small trickle charge through those parts. This was installed at the factory and is supposed to "inhibit corrosion".

Check with some GM dealers/assembly plants, maybe they can shed more light on this.

I think those are the ground straps.

Whatdaya bet that that the GM dealers are told to tell customers that line of B.S. If you think about it, any vehicle that has an electric clock, or a radio with preset stations constantly has a "trickle charge" running through it even when turned off (albeit not much). And when running, any electrical component runs a "charge" through the entire body of the vehicle for the current to get to ground (the other post of the battery).

Yeah, follow the Negative terminal on the Xterra if you want to see what it looks like for the Xterra.

EVERY VEHICLE has a connection to ground!
I think its funny that a dealer would say that it creates a trickle charge to inhibit corrosion.

Typical dealers if you ask me.

No they were not the ground straps. They were seperate from the regular electrical and grounding system. :rolleyes:

I'm not gonna pretend to be an expert in this area, but I know enough to be dangerous!

It was a seperate bolt on electrical box with leads from the battery going to the body panels. The cover on the box said something about it being an "electrical body panel corrision inhibiting system" or something to that effect (can't remember exact wording now). I will try and get a pic.

I'm not saying it was legit or it actually works, it's just what was there. I agree though, that it's probably just a "gimmick" item by the dealers.

Eh?

You can complete a circuit with most of the body panels, and certainly the frame/bumpers/etc.

The Zn doesn't care if it is 2 feet underwater, 10 feet underground, or just wet from road spray. It certainly doesn't have to be submerged. There just has to be some source of water - the same source that would cause your vehicle to rust.

Your vehicle is not going to rust unless it is somehow getting wet - be it from rain/snow/high humidity.

You put the Zn where it will be most exposed to the water, and it corrode rather than the iron - be it the frame, body panel, or whatever is in metal to metal contact.

There is already an electrical path from front to rear bumper, all the way up to the roof, the only panels I don't know about are the doors.

Tim

hahahahah,, Tim, I'm a Mechanical Engineer and I feel your pain man! Looks like i got to this post a lil late and it was frustrating reading some of the posts.. And some say college is worthless...........

Good reply, couldn't have said it any better myself.
-Crhis

I'm not a chemist, I'm an electrician.

What you have here is half a circuit.

Say you put the Anode at the front bumper of the car.
There IS an electrical connection from the rear bumper to the anode in the front bumper through the chassis.
But to complete the circuit you need to have current flow from the anode(front bumper) back to the rear bumper.
This is where the seawater and moist dirt comes in. It gets even harder when you realize you need to have the current run to every inch of the chassis.

This is where you are incorrect. You have the entire circuit right there in that chunk of iron, otherwise rust wouldn't occur. Consider the following:

The iron in one part of an iron object behaves as an anode, and the iron is oxidized to Fe2+:

Fe(s) -> Fe2+ + 2e-

The electrons produced in this half reaction flow through the metal to another part of the object, which acts as a cathode. Here atmospheric oxygen is reduced in the presence of H+(aq) supplied from H2CO3 formed from dissolved CO2:

O2 + 4H+ = 4e- -> 2H20

THE CIRCUIT IS COMPLETED BY THE MOVEMENT OF IONS THROUGH WATER ON THE SURFACE OF THE IRON. The overall reaction is the sum of the cathode and anode reactions:

2Fe(s) + 02(g) + 4H+ -> 2Fe2+ + 2H2O

The Fe2+ is further oxidized by atmospheric oxygen to rust:

4Fe2+ +O2 + 4H20 -> 2Fe2O3(s) + 8H+

NOW, we have see that the iron corrodes by becoming the anode of an electrochemical cell. However, IF WE CONNECT THE IRON TO A MORE EASILY OXIDIZED METAL SUCH AS ZINC OR MAGNESIUM, THAN THIS METAL BECOMES THE ANODE OF A CELL AND IT CORRODES INSTEAD OF THE IRON.

The Zinc supplies the electrons to the reaction. Now, you being an electrician understand that it doesn't matter how far away the source of those electrons are, as long as they are connected by conductor to what would have been the anode.

You can test this - take two non-galvanized nails, connect them with some copper wiring, wrap some Mg ribbon around one of them (this being the front bumper w/ chunk of Zn) and mist them with some salt water. The Zn will corrode, and the nails will remain non-rusted.

You can continue to argue that this won't occur, but any basic chemistry text will tell you otherwise.

Regards,
Tim

If this were true then how come EVERY manufacturer doesn't put a chunk of Zinc on the chassis.

They could solve the rust problem for the simple cost of a few dollars per vehicle.

It's like all miracle products, if they could solve such a major problem why does rust persist?

Wrong. Rust is the result of a reaction of Iron and Oxygen. Water just helps the process along. the sacrificial annode works well on boats, I'm not sure how well it would work out of water, but the Chemistry is there like TimR pointed out.

Fine. Okay, you are right - it really doesn't work. The earth is flat, and the moon landing was a hoax.

How the heck should I know why car manufacturers don't put it on every car? Maybe because by the time rust becomes a problem - they could care less about the vehicle. Maybe because rust is less of a problem with modern steel. Maybe because dealerships like selling undercoatings. Maybe because they did some cost/benefit analysis and found that consumers wouldn't pay for it.

TimR

The reason it isn't used on cars is that it only work in water. A boat is in water a car/truck is not. Unless your a U-boat Commander. The zink put on aircraft is not just a chunk bolted somwhere, its actually a paint/primer/rust proofing that is put on the airframe. If you have ever seen the a military aircraft with a yellow green paint on the inside this is the zinc coating. Alot of time this is painted over on moder aircraft but can be seen in aircraft that are being build and haven't been painted yet or in older military aircraft like WWII bombers where they didn't bother to painbt over it in the interior.

In order for a zink anode to work you need ot have electrolosys and you can only have that in an ion solution (IE: non deionized water (fresh or saltwater)). Basically with a boat your making a battery when you put in water. The zink reacts before the other metals thus protecting the boat. So this would only help protect your X if you have a snorkle.
read the link that Storm posted earlier. Cathodic Protection for Cars

[ 02-10-2002: Message edited by: Xrugger ]

From the above website:


Zinc plating over the entire chassis does work as does painting the chassis, covering it with rubberized undercoating (which is really just thick rubbery paint), even spraying oil over it seals it (but the oil wears off).
Basically if you want to keep steel from rusting, cover it.

I agree with this. The principle this works on is that if the covering is scratched in some manner, the zinc will form zinc oxide and cover the newly exposed iron.

And I see that I am partially incorrect. The chemistry is right, and the situation I saw in my mind is correct, but it is not the one you are talking about. I see the undercarriage of the vehicle covered by road spray - and there being a path for ionic flow in that covering of water. I guess I don't see any difference between that and moist ground. You claim that wouldn't be a path for the ionic flow.

In any case, who cares - I don't enough to try it out, and I live in the rust belt. Two years of driving through salty winter roads and there is minimal rust on my vehicle.

Tim

Tell me about it, they don't call it Salt Lake City for nothing. In the winter the roads here are white from there being so much salt on the roads.
My solution is to goto a touchless car wash that has an underbody spray.
So far so good.