Zinc

[bkelly]

This one is for the techies-

Last night I was watching this program on Discovery about how they make stuff. This one was on caskets. Once of the very first things they do is weld a big zinc bar on sheet metal for for bottom. I'm no metallurgist so don't quote me on this, but it's purpose is to stop the outflow of electrons from the metal to stop corrosion. They said it was so strong that it actually attracts them and totally stops the metal from corroding.

It got me thinking, why not just buy a big chunk of zinc and weld it to the car? Would that not do the same thing as the casket? If this works, it would seem like you could do this with any car.

[Weasel73240Z]

They are protecting the caskets based on the "sacrificial anode" theory, like when you install zinc on a boat's rudder or outdrive. Sacrificial anodes are being used alot in concrete applications, they tie an anode to the metal rebars prior to pouring concrete, to halt corrorsion of the rebar. The anode degrades, but the materials you're trying to protect, doesn't. It has to do with electron transfer, and a bunch of other stuff that gives me a popsicle headache just thinking about it. Way to in-depth to try and explain how it works in a short post, and I'm not sure I'm capable of explaining how it works, even if I wanted to, .

I think the problem in an automotive application is that you would likely need many anodes, because some of the body panels are not attached in a way that they are "electrically connected". Although being unibody, maybe they are? With concrete, all of the rebar is tied together; in a boat, the entire boat is sitting in an electrolyte (water). I think (but sure as hell don't know) that the fact that a car sits on rubber, and is technically not "grounded", would keep the anodes from working properly. The other problem is that, by nature, sacrificial anodes are "sacrificed", meaning if they work right, they need to be replaced regularly.

I sure do love a good "could this work" discussion. Dissenting opinions always encouraged. Peace, Weasel

[hls30.com]

Now we know why Zamak parts never last-and our emblems corrode...they are all made from a Zinc alloy, and plated. Once the coating has a void, they're sacrificial...

Will

[Sailor Bob]

The true purpose of Zinc anodes on a vessel, is to prevent corrosion, but it is of a different type than would be encountered in a car - this may help:

Galvanic corrosion, often misnamed "electrolysis," is one common form of corrosion in marine environments. It occurs when two (or more) dissimilar metals are brought into electrical contact under water. When a galvanic couple forms, one of the metals in the couple becomes the anode and corrodes faster than it would all by itself, while the other becomes the cathode and corrodes slower than it would alone. Either (or both) metals in the couple may or may not corrode by itself (themselves) in seawater. When contact with a dissimilar metal is made, however, the self-corrosion rates will change: corrosion of the anode will accelerate; corrosion of the cathode will decelerate or even stop.

Not my words, but certainly a better explaination than I would have provided. I have seen vessels out of the water whose anodes were missing for some time and the effect was pits in the hull, rudder and other underwater components - some were large enough to put your thumb into, there was no rust.

The issue would be contact between two different metals - brought about by the extended immersion of the hull in water which doesn't happen with most cars.

[Weasel73240Z]

Good stuff Bob. But sacrificial anodes do have a place outside of fulltime "wet" environments. And they can serve a purpose even when dissimilarity of metals (i.e. based on the metals ranking on the "scale of nobility") is not an issue. Note - I didn't write this, I cut and paste this from an industry website. If anyone other than Bob and I care......

Reinforcement in concrete is cathodically protected by galvanically connecting a sacrificial anode, such as a zinc or zinc alloy anode, to the reinforcement, and contacting the anode with an electrolyte solution having a pH which is maintained sufficiently high for corrosion of the anode to occur, and for passive film formation on the anode to be avoided. The pH of the electrolyte is preferably at least 0.2 units, and preferably from 0.5 units to more than 1.0 units, above the pH value at which passivity of the anode would occur. The electrolyte may be for example sodium hydroxide or potassium hydroxide but is preferably lithium hydroxide which also acts as an alkali-silica reaction inhibitor.

Same basic idea, but instead of seawater, the electrolyte is part of the concrete mix (I think they would use potassium hydroxide).

What a great subject, if I ever tried to talk about this on my softball website, I'd be blackballed.

[Sailor Bob]

This has been very useful and informative - I think the lesson we have to remember is not to drive our cars in the ocean and/or if you intend to encase them in concrete - be sure to use Zinc anodes.

[Weasel73240Z]

Yeah, I'm not sure we learned anything Z related, but whatever, gave us something to talk about.

[JimmyZ]

Years ago I got a book called Electrochemical Metalizing. It talked about plating and building up surfaces. You'd have to take off each panel for this approach.

If you properly prepared your panels to zero rust then got a metallizing gun and sprayed... Well it would be an interesting experiment. (You could have a stainless coated Zlorean and be Darbi's dreamZowner!!!)

http://www.flame-spray.com/2wire.htm

In truth simply doing proper prep while down to bare metal during a refresh will yield you 10-15 years - possibly 20 years of protection. As for stuff behind the panel and in between panels you're kind of up the creek unless you undo the seams and treat the backside. (Quarter arches for instance)

As for most of us when confronted by a hole in a QP arch...

You can either replace the affected area or...

Sandblast at vaious angles and hope to richochet some abarsive media in a hole then blow/clean well and ospho followed by epoxy prime. Any sand left in the cracks will cause rust so be sure to get as much as possible out. A shop vac and compressed air go a long way. (Using the shop vac most)

I was once like you are now.. Trying to find a way to "permanently" protect the Z. Unless you operate it on a closed track there is more of a chance of it getting totaled than rusting away.

2c

Jim

[bkelly]

Interesting. I live in NY so if it's going to work, you can find out here in a short period of time. They dump so much salt on the road, it's like driving on gravel. My 06 has rust on it already! Maybe I'll get a piece of zinc and weld it to the main body of my car. Cars up here usually go 5 years before things get bad, then you can go 5 more before it's ready for the junk yard. My parents just got rid of a Taurus last spring that was 10 years old. Mechanically/cosmetically it was perfect..interior was brand new. The underside of the unibody was completely rotted.

[Weasel73240Z]

I think, because the underside of the car isn't "in" an electrolyte, a zinc on the unibody for instance, would only protect the metal in the direct area that the anode is attached too. Even in an electrolyte solution, it takes very specific conditions (i.e. a certain pH level for the electrolyte) for cathodic protection to work. I think there are too many variables if the anode is exposed to air and different weather conditions. Plus, if it could work, and I'm still not sure it could, you would probably need hundreds of individual anodes to protect the underside of a car.

And the last thing any of us want to do, is add weight to our Z.

[Sailor Bob]

I think the message was plain in previous text that this was not a solution to sheet metal rust in a car. If these cars were built using Galvanized plate or as stated earlier even painted better rust would not be such an issue.

If you really want to preserve your car, don't drive it during the salt season. I put my Z away at the first sign of snow and dont take her out till a month after the snow is gone, that allows time for the rain to carry away any salt residue. For that matter I don't drive it in the rain, unless I get caught off guard. To alot of our members this is not an issue, but to the salt belters I'm just repeating the mantra.

[240dkw]

Does anyone know if this product has any merit or is it more snake oil?

http://www.canadiantire.ca/browse/product_detail.jsp?PRODUCT%3C%3Eprd_id=845524443292139&FOLDER%3C%3Efolder_id=1408474396672466&bmUID=1200013858578&deptid=1408474396672395&ctgrid=1408474396672402&subctgrid=1408474396672466