Posted 2005-04-05 9:02 AM (#23442) Subject: Steel Frame Aluminum Body Electrolysis a myth!
Elite Veteran
Posts: 634 Location: Tipton, IN
Huh, got your attention didn't I. First, with an electrical current electrolysis could occur. But what we keep talking about on our horse trailers is not true electrolysis. It is Galvanic corrosion, where water acts as the electrolyte solution. In a dry situation you will not see this, such as in your electrical panel in your house where they use a steel box and aluminum conductive blocks. So where is the electrolysis in that then you might ask, there is none because there is no electrolyte or STRAY current. Anyway, galvanic corrosion only occurs when you have the electrolyte present. It's the same at home with steel waterlines and brass fittings, they use plastic washers to keep them from touching. Anyway, that is my understanding after much research, and feel free to correct me if I'm wrong.
Posted 2005-04-05 9:31 AM (#23446 - in reply to #23442) Subject: RE: Steel Frame Aluminum Body Electrolysis a myth!
Expert
Posts: 2689
Yes,
So ? (-:
BTW, it doesn't take "liquid water" as we know it, or an obviously liquid electrolyte, "ocean air" works only too well )-:
Also (I think this is right) PURE water won't act as an electrolyte, or is a very poor one.
Now, if Yer Gonna open up a steel/alumin structure and admit copious quantities of acid rain at the top or road salt/slush underneath, well electro-chem theory and strict definitions sort become irrelevant )-:
Errr, dry junction box in the basement... I think the description is that there IS an electrolytic potential, but it is across a poor conductor (dry air). I also think there is a careful selection of materials, e.g. the steel is galvanised (zinc coated) and copper is used as an intermediary.
We got too much time to thunk, need to get out and RIDE !
Posted 2005-04-05 9:48 AM (#23447 - in reply to #23442) Subject: RE: Steel Frame Aluminum Body Electrolysis a myth!
Elite Veteran
Posts: 634 Location: Tipton, IN
Reg,
Your right, pure water is not an electrolyte, and trailers in say Oklahoma, Nevada, Texas(non-coastal), and Colorado(uses sand on roads, not salt) don't see the same corrosion that coastal and northern states do. Primarily because they get rain water and no salt. In the northern states where we use salt on the roads you tend to pick some up, and when the pure water and that salt residue mix is can act as an electrolyte. SO keeping your trailer washed is of utmost importance. ANd I am one of many that neglects to do that as often as I should.
Posted 2005-04-05 10:32 AM (#23450 - in reply to #23442) Subject: RE: Steel Frame Aluminum Body Electrolysis a myth!
Veteran
Posts: 109
OK, pure water as a chemist is defined when it has a conductivity of 18.2 mega ohms. It will conduct but not well or easily. So there is little or no galvanic action. A good analytical chemist will always never say zero, we just have not figured out how to measure that low. The ability of water to carry a current comes from the ions in solution, the seawater is a good example. The ions move from a positive to negative pole as would a battery and then form a stable compound, i.e. rust, iron oxide. This can also have a beneficial effect as it can protect the base metal from corroding further, the green patina on copper. This green patina protects as long as it is not damaged and will kept the rest of the metal from further corrosion.
Now from my understanding on the aluminum skin and steel frame trailers is what Trail-et has done is worked with 3M. They place a strip of material that separates the two dissimilar material. As the two do not touch you do not get the galvanic action and it acts as the green patina on copper materials. If you get damage to that material then you now get the galvanic action. So if you live in a area where salt is used on roads washing is good. This removes the salt, Calcium Chloride in most areas now, by washing it away from trailer. The chloride here is the problem, what you get is zinc chloride forming. Zinc is the used to portect the iron in steel which just naturally will oxidize with water from the air/rain.
Also if you get damage to the skin of the trailer and have to remove a panel make sure that you replace this insulator so as not to get the reaction going.
Posted 2005-04-05 12:08 PM (#23458 - in reply to #23442) Subject: RE: Steel Frame Aluminum Body Electrolysis a myth!
Member
Posts: 22
Location: Sidney BC
don't forget too that if you have horses that get a bit antsy trailering or are put inthere hot and steamy, the sweat is THE worst thing for the inside of the trailer. thats where the salt comes from. luckily our guys trailer quietly and well and rarely sweat up in there (unless its hot outside). but we trailered a friends horse and the damn thing weaved and rocked and sweated its way to the destination. when we got it out it was like a sauna in there and we had to take the pressure washer to the inside to get rid of all the salt - steel OR aluminum isn't gonna like that!
Posted 2005-04-05 2:47 PM (#23468 - in reply to #23442) Subject: RE: Steel Frame Aluminum Body Electrolysis a myth!
Expert
Posts: 1989 Location: South Central OK
Rodent, one thing I do in the summers around here is before I load up I hose off the horses. This keeps sweating to a minimum. The horses arrive clean, cool and calm.
Posted 2005-04-05 6:22 PM (#23474 - in reply to #23442) Subject: RE: Steel Frame Aluminum Body Electrolysis a myth!
Member
Posts: 22
Location: Sidney BC
huntseat.. its not that its that hot in there, its just that idiot horse that belongs to friend insists on piaffing all the way to whereever we go. I think she thinks its a flintstone vehicle and she has to run the whole way!!! very annoying. so by the time you've gone half way round the block she's sweating buckets. hubby said last time we trailered her it would BE the last time.. sick of having to clean out the trailer every time!
Posted 2005-04-06 8:54 PM (#23515 - in reply to #23442) Subject: RE: Steel Frame Aluminum Body Electrolysis a myth!
Extreme Veteran
Posts: 378 Location: Nebraska
The problem is two different metals (steel and aluminum) that expand and contract at different rates when thermal heating or cooling is applied. The friction induces a small electric charge (static electricity), which in turn causes oxidation, and eats away at the metals. To prevent this, hopefully some kind of insulation has been added between the metals.
Posted 2005-04-06 10:10 PM (#23518 - in reply to #23515) Subject: RE: Steel Frame Aluminum Body Electrolysis a myth!
Expert
Posts: 2689
Originally written by hconley on 2005-04-06 8:54 PM
The problem is two different metals (steel and aluminum) that expand and contract at different rates when thermal heating or cooling is applied. The friction induces a small electric charge (static electricity), which in turn causes oxidation, and eats away at the metals. To prevent this, hopefully some kind of insulation has been added between the metals.
Errr, NO.
The elecro-potential is there by the nature of the metals, it has nothing to do with their different coefficients of thermal expansion and/or any resulting friction between them.
They can DO THIS WITHOUT TOUCHING EACH OTHER - I should be so luc{censored}
Posted 2005-04-06 10:25 PM (#23519 - in reply to #23442) Subject: RE: Steel Frame Aluminum Body Electrolysis a myth!
Member
Posts: 46 Location: New Mexico
So what does all this actually mean. Is a steel trailer with aluminium skin going to disintegrate before our eyes? How long will this process take, two years, 10 years, 20 years? Is something else going to give out on the trailer before this process has a significant effect? It seems as though there are still many of these kinds of trailers being made. Are some manufacturers doing more to prevent this than others? It just doesn't seem like it is a big problem from what I have read. Even Neva Scheve that wrote the trailer buying book doesn't make it out to be a problem and that book was pretty detailed about what to look out for.
Posted 2005-04-07 6:07 AM (#23524 - in reply to #23519) Subject: RE: Steel Frame Aluminum Body Electrolysis a myth!
Expert
Posts: 2689
Originally written by Babygoose on 2005-04-06 10:25 PM
So what does all this actually mean. Is a steel trailer with aluminium skin going to disintegrate before our eyes? How long will this process take, two years, 10 years, 20 years? Is something else going to give out on the trailer before this process has a significant effect? It seems as though there are still many of these kinds of trailers being made. Are some manufacturers doing more to prevent this than others? It just doesn't seem like it is a big problem from what I have read. Even Neva Scheve that wrote the trailer buying book doesn't make it out to be a problem and that book was pretty detailed about what to look out for.
ANSWERS:
No, Variable, perhaps/probably, yes.
The original post was a clarification of terms, the difference between electrolysis and galvanic action, etc., it was also a bit of a "hook".
We almost always wander to the relative merits of steel and aluminum. It is my belief that good and poor designs are possible in each, as well as the combination of both, i.e. you really COULD get the best or worst of both worlds by design (or implementation).
Another point that is often raised is the properties of aluminum as an element or as a common use alloy, this is NOT the stuff that trailer builders are using (-:
There is at least one excellent article on designing with aluminum on the Lincoln electric web site. Very early on in the article it makes the point that one of the WRONG ways to build from aluminum is to just select the "strongest" alloy, size the section for the equivalent strength of steel (Joe, just use thicker section) and go ahead and build your steel design.
There are probably as many wrong ways to design and build from steel (-:
Posted 2005-04-07 8:00 AM (#23526 - in reply to #23442) Subject: RE: Steel Frame Aluminum Body Electrolysis a myth!
Elite Veteran
Posts: 634 Location: Tipton, IN
I think thee are good and bad points for all aluminum, aluminum/steel, and all steel. And I agree with Reg, design is everything. I own a steel frame, aluminum skin trailer, and have yet to have an issue other than due to my lack of washing it as often as I should.
Posted 2005-04-07 9:53 AM (#23528 - in reply to #23442) Subject: RE: Steel Frame Aluminum Body Electrolysis a myth!
Extreme Veteran
Posts: 455 Location: Ontario - east of TO
Any aluminum trailer has some steel though - the coupler and the axles are always steel - so you have to make sure the "tape" is used.... When i was shopping I asked - most dealers know exactly what you mean - and personally I'd steer clear of any who do not.
Posted 2005-04-07 10:06 AM (#23529 - in reply to #23442) Subject: RE: Steel Frame Aluminum Body Electrolysis a myth!
Member
Posts: 46 Location: New Mexico
Are there any good websites that explain this well and what to look for etc? I have a steel frame/aluminum skin trailer for sale and a couple people stopped even considering my trailer when they found out it had this contruction. I could hear one ladies husband in the background telling her that the trailer would fall apart because of the steel/aluminum contact. Don't know if that alone has cost me the sale but I feel like it was a big factor. Where can I refer people if they have concerns? I feel like my trailer(CM) is well built and I'm not worried about it but I would at least like people to be able to get the right info before decided not to go with this construction. I know some people just don't feel comfortable taking the chance and I'm okay with that if I feel they understand it.
Posted 2005-04-07 12:20 PM (#23534 - in reply to #23529) Subject: RE: Steel Frame Aluminum Body Electrolysis a myth!
Expert
Posts: 2689
To some extent you're dealing with people's perceptions and emotions, they (me too) may just have it implanted somewhere in the psyche that manufacturer X or Y has never made a good trailer and never will, manufacturers W and Z have always made perfect ones, etc. BTW this is also true with autos, trucks, motorcycles, boats, on and on. I don't think it is any different with materials or choice of constructions methods. Some of us want to play amateur designer, metalurgist, engine ear, etc., and second guess those that were paid good salaries to do it as a full time job. It is probably a waste of time searching out web sites to present people with "PROOF" that what you are trying to sell is OK. Many of us can create web sites and put whatever "expert opinion" we want there.
You may be better off to just wait until someone comes along that is looking to buy what you have, or doesn't understand if there is a potential issue (-:
Steel Frame Aluminum Body Electrolysis a myth!
