I've done a search here and on the web concerning electrolysis when aluminum touches steel. I see that several people here have acknowledged it, but no one has really described the effects of it. How bad is it? What will it do to the metals? How long before I actually need to be concerned about it? What should I do to prevent it?

In my web search I found some slime called ECK to inhibit the effects of electrolysis. It's at www.vannay.com/eck.html Anybody ever try this stuff?

I'd like to custom make a 1/4" thick 2024-T4 aluminum skidplate. I got sick of how much my 1/8" mild steel skidplate was deforming and re-morphing itself, especially after it rubbed against the transfer case and other parts. So I want something that'll deform less, without the added weight of thick steel. And I'm thinking 2024 because it's slightly stronger, harder, and resists cracking more than 6061. I won't need to weld it - just bend it a little and bolt it to steel.

Thanks!

"How bad is it? What will it do to the metals? How long before I actually need to be concerned about it? What should I do to prevent it? "

Ask a rover owner :)

I use black death aka super black weatherstrip adhesive to isolate my panels. I also only mount painted steel to painted aluminium. You can also buy little rubber washers and what I find best if it is possible to use, rubber gasket material.

It will corrode the aluminium quite quickly, but to hole 1/4in or do any real damage would take a while.

Do as I say above and it will be fine.

Search also galvanic corrosion

Ron

With 1/4" thick Al material, it would definitley be on the order of many years before significant damage would occur. Al is pretty sensitive to electric charges passing through it. I know the Al boxes that hold the electronics in airplanes are coated with Chromium to prevent them from being damaged. You might look into a light Chroming procedure. The plane pieces I've seen still look like Al for the most part, you can't even tell the coating is there (visibly).

Paint the steel and put some silicon where the bolts pass thru., and it will be many years it corrodes.

for big items like you describe, I wouldn't worry about it. It's real bad for radiators and things that can plug up or have a small cross sectional diameter to corrode thru easily. I isolate my rad from the mild steel, and bolt my t6 skidplates to the frame solid.

I used to work on helicopters that had a magnesium skin and structure that we patched with aluminum panels. These materials will also rot on another over time. We used to use a super top secret method to prevent this:

Clear packing tape! It seemes to work to!

I've also been concerned about the electrolysis since I'm considering an aluminum tub for my FJ40. All the bolts, and bolt-on items that will be installed on it are steel.

Here is what the tub vendor (http://www.cruisersolutions.com/aluminum.htm#pricing) says about electrolysis:
<I>

Myths About Aluminum Bodies
1. There is one common myth about aluminum body tubs: Where aluminum and steel meet, electrolysis will occur and weaken the metals. It is scientifically true that electrolysis will occur between different metals, but it's only a significant factor in marine construction where the metals are immersed in water over a long period of time. These conditions simply don't occur on a vehicle. The fact is, it's not going to happen in a motor vehicle with an aluminum body. Think about the ways aluminum and steel have been successfully used together for many years. Most aircraft, for example, combine aluminum and steel. In automobiles, the legendary Shelby AC Cobra has an aluminum body and a steel chassis. Chevrolet's new Corvette, the new Audi A6, and even the noble Bentleys and Rolls Royces of yesteryear, have been crafted of aluminum and steel in happy combination. In summary, don't worry about electrolysis. It occurs, but so slowly and minutely that it's almost like watching the wind erode the Great Pyramids.

</I>

I'm sure these guys are a little biased, but is what they are saying close to the truth or complete B.S.?

If you paint both the aluminum and steel components you are bolting together and maybe coat the bolts with something (?) would you be OK?

Cruiserhaven -- ya a little bias on those guys. Still I've pulled apart Austin Healeys for restoration. They have a steel body with an aluminum trunk. The flange will quite often need some TIG work to repair the aluminum panels. Usually these restoration projects were long since neglected being stored outside, etc.

For marine applications it is why ZINC sacrificial anodes are bolted to the aluminum. You need to look at a galvanic chart to see the potential difference between metals.

On the aluminum.... USE 6061-T6 as your skid plate, NOT 2024! 2024 is stronger, but not as corrosion resistant. You'll really need to have the 2024 anodized! I used 6061 Skid plates on my Pro Rally vehicle... never noticed any problem after some years. Large contact areas, so any corrosion is spread across that area of contact. No isolation barrier, just bolted up. Chromate primer will help, but not required.

I had no way of bending my skid plate, other than a floor jack and the weight of the vehicle. Well when running around California City I kept getting air borne, and landing hard on the sand. At the end of that event... nice custom fit skid plate with a smooth curve around the cross member! Looked great! :D

Tom :usa:

So when I put in my aluminum Radiator connected to my iron engine block, I should put a zinc anode in?

Originally posted by schuss
So when I put in my aluminum Radiator connected to my iron engine block, I should put a zinc anode in?

depends. do you have rubber or conductive hoses?:flipoff2: :confused: you should be more concerned about mounting it to the frame.

Originally posted by Aggro


depends. do you have rubber or conductive hoses?:flipoff2: :confused: you should be more concerned about mounting it to the frame.

on the frame mounts I can just put rubber pads or something in. I will be using Rubber hoses, so I guess it won't be a problem.

Originally posted by DUG
Clear packing tape! It seemes to work to!

Probably the simplest solution so far. We used this when we were making $600,000 buses :eek: :eek: and guess what, no problems :D :D 5 years and still working :D

Originally posted by roundrocktom


On the aluminum.... USE 6061-T6 as your skid plate, NOT 2024! 2024 is stronger, but not as corrosion resistant. You'll really need to have the 2024 anodized! I used 6061 Skid plates on my Pro Rally vehicle... never noticed any problem after some years. Large contact areas, so any corrosion is spread across that area of contact. No isolation barrier, just bolted up. Chromate primer will help, but not required.

Tom :usa:

What thickness should be used?? And what about making bumpers from the same material.

How much weight saving are looking at in two indentical bumpers/skid plates, one made of steel and one of aluminium???

I would use 6061-T6 as well, 1/4" minimum... Identical ARB type bumpers will be 30-50 lbs lighter in alum. Also, anodizing will really help galvanic reaction and oxidation...

"These conditions simply don't occur on a vehicle. The fact is, it's not going to happen in a motor vehicle with an aluminum body"

COMPLETE and TOTAL BS They obviously don't know jack and I would be hesitant to buy something from them if they are going to tell you stuff that is blatently wrong.

I have enough rotted alum. rover panels to prove otherwise. isolate or watch it rot through.

Check any range rover with the sills under the bonnet where the front wings bolt on and they have begun to rot.

Ron

Originally posted by Gozuki
I would use 6061-T6 as well, 1/4" minimum... Identical ARB type bumpers will be 30-50 lbs lighter in alum. Also, anodizing will really help galvanic reaction and oxidation...

Thanks for the info, I was thinking 3/8" would be my cup-o-tea. Now I just need to convince my boss to set me up with TIG :D:D:D

I don't know about anodizing, maybe I'd just put some type of poly bushing in between the two, and a sleeve around the bolt.

A friend of mine patched his '83 FJ40's tub with aluminum a couple of years ago...All he ever gets out of me when I ride with him is crap about how his floor looks like cottage cheese :D

If you must do aluminum, go down to your local marine dealer and pick up some zinc diodes, and gorund everythign you can to them. they'll rot really fast, but it will protect everything else as long as you replace them when you need to (every year or two)

zinc diodes do not help much in a vehicle application.

First off lets get a couple things strait. The is aluminium and then there is the aluminium commonly used in vehicles. The former will corrode and rot away, the latter is usually an alloy with mag. in it and has the advantage of not rotting away in a normal enviroment even if left unpainted. The reason being that it corrodes and forms a very hard surface of corrosion on it that prevents further deterioration. It also makes it a PITA to paint.

Upside is you can dig a rover floor panel out of a backyard in canada and it will be fine, but you leave it on the truck touching steel and the paint bubbles in a year.

If you have an aluminium body or any aluminium body panels you have to paint with an etch primer or etch and then prime immediately. Otherwise it will just flake off.

If you use automtive style alum for panels you have to isolate it from steel. Any steel and especially stainless steel. A good idea is to use galvanized grade 5 bolts as zinc is close enough to alum to not create too much of a problem (I still isolate galvanized steel from alum and you should too).

Any place it contacts steel isolate the two, no excuses.

Alum is wonderful stuff for body panels, lightweight, no need for paint etc. it just needs a little special treatment.

Ron

Thanks for all the info. I was checking into local anodizing shops today to see if that's even a realistic possibility. Didn't hear back yet. Otherwise, I'll just stick with 6061-T6. I was originally hoping that painting the 2024 would suffice. I wouldn't think it would rust any faster than my steel rock sliders that I have to keep repainting.

My front bumper is 6061-T6, 3/8" in all critical areas, with 1/4" in the lesser important areas, such as the top and bottom near the outside. (I thought there was some 1/2" in there too, but I just learned there isn't). It's basically a giant C channel. My bumper was custom built by www.denveroffroad.com - he does awesome work, but he charges an arm and a leg. I've slammed it very hard into rocks and didn't do any damage. Steel brackets extend off the frame to bolt to the aluminum. So I should apply this knowledge about corrosion to that as well now. The aluminum portion of my bumper weighs only 53 pounds (plus add the steel brackets). Aluminum has 1/3 the density of steel. In comparison, I know a complete 1/8" steel ARB Prado bumper for my 4Runner would weigh 104 pounds.

What thickness should be used?? And what about making bumpers from the same material.

How much weight saving are looking at in two indentical bumpers/skid plates, one made of steel and one of aluminium???

On the aluminum, as someone pointed out it is 1/3 the density of steel. Typically I'll use aluminum about 50% thicker in a given application. As an example for a bumper: 1/4" steel is fine, 3/8" aluminum is just about right on the money. End result, the item out of the aluminum is about half the weight when compared to steel for the same same strength.

1/4" aluminum skid plate should be fine. I have used 1/4" on LIGHTER vehicles (2500#). If you have a three ton monster, the 3/8" thick plate would be better. :D

When you ask your boss for a TIG welder, go with the 500 Amp three phase machine... you'll be able to weld up to 1/2" aluminum plate in a single pass. :D

THANKS for the idea of clear packing tape. I forgot about Rovers, but I have seen different aluminum alloys in the healey's. Some fair just fine, others do rot badly. Usually the aluinum panel was pretty thin up against a steel frame member. No need to unbolt the panels, just tug on them! :)

Tom :usa:

It is all a matter of metalurgy, you guys made me break out my class notes.
It really depends on the alloys of steal and aluminum used.
The term for this type of corosion is Galvanic corosion, not electrolosys, even the reaction stems from the transfer of electrons from the anode to the catode. Aluminum is a more reactive metal than steel is, but not by much.
I really would not worry about it two much, especially if the skidplate will be large. The Aluminum acts as the anode and somewhat protects the steal from corosion by supplying it with electrons from the decompostion of the aluminum. With a large cathode the decay will be spread over a larger area, meaning it will probably be at least 20 years before it is visible.
With a skid plate It should not really be an issue, especially a 3/8" thick one. Painting aluminum is a pain in the ass.

Cool. Thanks.

In case anyone else is also looking for a cheap aluminum supply store, I just found www.yarde.com and then go to their "drop zone" for buying their remnant pieces. Their prices look like 1/3 of what it would be if I ordered that size to be cut. For example, they have a bunch of 1/4" x 24" x 48" plates of 6061-T651 for about $55. Sounds awesome to me.