Aluminum to Steel

[Firegirl]

Well Fellas, I'm almost done with the sculpture! I welded the steel pieces with the ARC and I have an industrial strength product from Devcon called 2-Ton Transparent Epoxy...The last of it is curing now and seems to be doing just fine. The glue even held up to the piece being dropped before it was fully cured I should be able to post a picture by the end of the day. Thanks for all your help, I'm gonna keep it in mind for the NEXT project I do with modern techniques...

[ertwdan]

Any time that you bond Aluminium to steel you will have a corrosion problem unless you seperate them electrically. This is done in the marine industry when they attach an Aluminium cabin to a steel hull. The adhesive method will seperate the metals to prevent the galvanic reaction and keep things from rusting too quickly.

[Hillbillysmith]

You can join the two by soldering them. It can also be done by brazing, but this is NOT easy for the average hobbyist.

[irnsrgn]

And remembering that Soldering, Brazing and Welding are all Heat Ranges, not necessarily the using of one specific material or alloy per se. For instance, tiging with silicon bronze is actually brazing as is the use of bronze to braze cast iron.

[Joe H]

I build customs signs, and we use adhesives alot for certain things where welding isn't the best option. One thing I have learned is that gluing steel to aluminum works ok for indoor applications. If it's going to be outside it will fail. Aluminum to aluminum, or steel to steel will last indefinately, but dissimilar metals just do not work. The reason is different coefficiants of thermal expansion. One metal expands/contracts more than the other, and it is only a matter of time before the glue is ripped apart.

I have actually done experiments with many different adhesives in attempts to find one that will work. What I have done is glue some Al to another piece of Al, a piece of steel to a piece of steel, and some Al to some steel. I'd put all 3 pieces in the sun for awhile, then toss them in the freezer overnight. It usually only takes one of these cycles before you can break the aluminum and steel apart by hand, even though the similar metals are strong as ever.

We spent many thousands of dollars in warranty service work before this sank in good. Now, gluing aluminum to steel is near the top of our list of no-no's.

Silver solder would likely be a good choice for you if a mechanical means of attachment is out.

[irnsrgn]

Joe, I am wondering if the solution to your sign problem is sandwiching a buffer material between the Al and Fe so that the expansion and contraction does not affect the bonding material. ie, a thin strip of silicone, weather stripping, etc.

[clang]

There are a couple of multistep methods Firegirl, but they are a nuisance.
I read a 1930s method than ran to 13 layers and another , later one that ran 7 layers.
There is, or was, an AC aluminum-bronze rod that will deposit on freshly scraped aluminum and an AC phos-bronze rod that will lay down on that ,as well as steel. A little tricky but possible...pf

[chiso]

That is what it is called. The Australian navy mine sweepers??? Used to have there ships made with steel hulls and an aluminium deck to keep the weight down. But in an explosion they found that the deck pealed away from the hull.

Would cost a fortune to do.