Frame rust- when to do?

[ld50]

Now I`m going to have to restudy my corrosion books!

It seems like a good idea, why then, wouldn`t automakers incorporate this into every car?
Maybe they like rust?

I`m going to run this by a bona-fide elec. engineer at work. I`ll get back to you!

 

[dogfriend]

I took a graduate level class in corrosion when I was in school for Material Science.

In theory, applying a counter emf (against the normal voltage caused by the different materials present in the corrosion cell) will inhibit the corrosion process.

In reality, I'm not sure how easily this can be applied to the many different components of a typical car frame and body. (i.e. how does this affect other parts (alternator case, radiator, transmission case) which are also grounded to the frame of the vehicle?)

I think that the car manufacturers rely more on protective coatings because you can also inhibit corrosion by preventing the electrolyte from contacting the material. It is probably more reliable and cost effective for them to do it this way.

 

[ld50]

I work in the oil and gas industry, and we use a system where current(electric charge) is induced into our main pipeline (1200kms long) at regular intervals.

The idea is that buried pipelines will eventually build up a charge on their own because of the earth`s magnetic field. Experience has shown that most pipeline corrosion will occur at a point where the wrapping around the pipe has failed, and this current is allowed to discharge to earth. Of course as you already seem to know, this speeds up oxidation (rust).

So the pipeline (and tanks) have a little extra charge induced into them and along the way there are buried "anode beds" connected directly to the pipeline. These are basically around a dozen magnesium/lead poles that are uninsulated and buried.
Since electricity follows the path of least resistance, in theory, it will leave the pipe at these locations, and not tend to be lost in spots with damaged wrapping.
As you pointed out, rust is caused by an electro chemical reaction, and these anodes rust very quickly.

I had pondered using an anode connected to a vehicle with a ground strap coming off it before but thought the neg. ground was a big problem with the theory.

I`ve only had the most basic of corrosion training, and don`t work in the corrosion department, but i did find it interesting!

 

[dogfriend]

The most significant thing that I remember from the corrosion course that I took was that thermodynamics says that your steel body on your automobile is doomed to revert back to a pile of Iron Oxide (rust). The free energy for this reaction (iron to iron oxide) is a large negative number which means that the product (iron oxide) is much more stable than the steel or iron. This makes sense to me. They never dig to find chrome - moly tubing underground; they mine raw iron ore and put in a bunch of energy to transform it into the tubing. The tubing is at a higher energy level now. Entropy says that it must eventually revert to the lower energy form (rust).

The only part that you have some control over is the kinetics (rate) at which the reaction occurs. If you paint it to keep electrolyte(s) away, then you slow down the reaction. If you immerse it in salt water (or even better sulfuric acid) you speed up the reaction. If you live in Buffalo NY (near where my GF grew up) you have a much better supply of electrolyte than if you live in Sacramento CA where the electrolyte isn't so good

Another interesting concept related to rusting car bodies is that you do not have to have dissimilar materials to set up a corrosion reaction. You can also get a corrosion cell by having areas with a different concentration of oxygen available which are also in electrical contact. This reaction is called crevice corrosion. So if you have a seam on your car where the paint is thin or missing, the concentration of oxygen will be higher than the areas where the paint is normal. This sets up a corrosion cell where the area with lower concentration is anodic and the seam with higher concentration is cathodic. Eventually you get rust, but not at the seam; the rust starts under the paint nearby and then eventually the paint comes off as the rust grows and flakes off.

 

[ld50]

Well I`m still investigating this anti-rust deal.
I talked to our resident Elec. Engineer, and he said there was a product available in Canada many years ago that similiar to what was described to me. Unfortunately, this company was ordered by the government to stop selling this product after several people sued, and the subsequent investigation found that the system didn`t live up to it`s claims. Apparently, the vehicles still rusted.

He seemed to think that this product came up from the US, and was still available in some States, but had beened banned in others.

However, he also said that what jaybyrd described seemed different than the system employed by the sued company (It was called "Rustbuster" or something like that).
It peaked his interest, and he promised to look into the idea more, by asking some of his Peers in the Elec. Eng. field. His only concern was the effect of crossing streams and submerging the frame in water(?)

I actually found out that an electrician at my work installed something like that on his truck as soon as he bought it, They say he swears by it, so I am going to try and question him about it tomorrow, so I can make a decision based on info from different sources. I`m going to search the net as well.

Merry Christmas Yule Tides!

 

[dogfriend]

check this out

http://www.jcwhitney.com/productnoitem.jhtml?CATID=4504&BQ=jcw2

I'm not endorsing this product in any way; in fact, I'm pretty sure it won't work, but that never stopped anyone from trying to sell it anyway.

This is also different than what jaybyrd was describing, but more typical of the systems I have seen for sale.

 

[ld50]

Ack, I forgot about this thread what with the holidays and all!

I talked to the guy at work that has the antirust deal in his truck (he`s the elecrical dept supervisor) He said the unit was offered by Toyota when he bought it new last year so he decided to get it. If it`s anything like undercoating it should be great right (wink).I figure I`ll wait ten years or so and see firsthand if it works or not. I`ll post again with my findings in 2013.

-over and out

 

[HH1]

Nice pooper Hartman!

 

[Partwerks]

Basically what you need to do is take the voltage from your battery and invert it to output low amperage high voltage (400-450 D.C. Volts ), and at 3 or 4 points around the vehicle you send this voltage into the frame and chassis through capacitive couplers, essentially turning your entire vehicle into a giant coupler with the vehicle acting as the negative plate and the capacitive coupling points as the positive plates. The charges are localized but continually hold an overpotential on the metal surfaces of your vehicle thanks to the insulating layers of paint on the body. So while normally during corrosion OH- are being generated as a byproduct of the iron giving up 2 electrons, the constant field charge of the coupling effect your vehicle now has stops the chemical reaction from shifting electrons to the right. This is especially important in preventing chips, and scratches from starting the initiation step in the reaction of Fe(solid) = Fe - 2e- which in turn would normally generate oxidizing hydroxyl groups when mixed with moisture or good old H2O.

Should also be noted that because this is DC voltage with almost no Amperage it has absolutely no effect on your vehicles electrical systems or computer. I mean your could hold on to a million volts with your tongue as long as there was no amperage.

Hope that helps explain it a little better. Don't have pics or drawings but I'll see if I can borrow a digital camera and show everyone my setup and lack of rust looks like.
I'd even be willing to put together some kits if enough people are interested. I could sell them for about $50 with a profit to me of around $10 per unit.

Are you doing the kits?