Aluminum vs. Steel

10brink · 10-12-2007, 07:48 AM

I'm attempting to fix a rear end sag, separation, on my '67 Safari and have read every imaginable thing I can find. Andy, at Inland, has extensive commentary on the proper fix and I'm trying to follow that advise. There are NO broken or cracked floor channels, just bigger holes where bolts were pulled through the channel. (PO had an 85 lb piece of 4" angle iron and a welded on trailer hitch, bolted to the rear bumper. Who knows what he pulled or how far) I'm going to put 1/4 inch steel in the bottom of the channel, as advised, but I keep reading about the deleterious effects of combining steel with aluminum. I came across a thread once, and I want to attribute it to Andy (Inland), but now I can't find it, that said this advise was mostly bunk and that there were plenty of places on AS's where differing metals meet up. Also, can I use angle iron in that channel, cut, bent, and welded into a single piece to follow the butt end and the curve? I'm thinking I can rivet the exterior skin back through that angle iron and aluminum channel. Angle iron's stiffer than flat steel. Yes, I know I'll need to address the axle, balance issues, but I need to get this rear end thing done before it gets too cold. I'll worry about the other stuff later. Andy, if I've attributed something to you that you didn't say, please let me know. Sorry in advance!

LoydBonifide · 10-12-2007, 08:27 AM

Galvanic corrosion occurs when dissimilar metals are connected, especially in the presence of an electrolyte (water). This link is a guide listing various metals and their relative galvanic reaction.

Galvanic Corrosion Guide

You will see in the guide text that metals close to one another have the mildest reaction, with steel and aluminum right next to each other.

The effect will be the least, but still a possibility. It can be avoided by a barrier, such as a gasket or paint.

byamcaravanner · 10-12-2007, 09:10 AM

10brink,

You can place nylon sheet or similar (available from a place like McMaster-Carr) between the dissimilar metals to isolate them from each other.

Aerowood · 10-12-2007, 09:19 AM

Steel and aluminum are used in the aviation industry all the time. The key to success is having both pieces properly preped, primed, and painted and then sealed between the mating surfaces. I will agree that it is best to have aluminum to aluminum, but corrosion can happen between these two mating surfaces if both parts are not primed and sealed together. If Airstream had properly primed and sealed all the mating surfaces during assembly it would have basically eliminated all seam leaks and corrosion issues.

Kip

10brink · 10-12-2007, 03:22 PM

Thanks, everyone, for the responses. I can go ahead with the steel and feel ok about it. I'll just prep it well. If anyone will weigh in on my angle iron issue, I would greatly appreciate it! I only want to do this once. Ain't gonna' happen again.

byamcaravanner · 10-12-2007, 03:45 PM

Quote:

Originally Posted by 10brink

Also, can I use angle iron in that channel, cut, bent, and welded into a single piece to follow the butt end and the curve? I'm thinking I can rivet the exterior skin back through that angle iron and aluminum channel. Angle iron's stiffer than flat steel.

You certainly could do this but I don't think it is necessary. The purpose of the 1/4" plate is to spread the force transfered through the floor bolt to a wider area of the aluminum channel. this will make it less likely to tear-out. A 2" to 3" piece at each bolt should be more than enough.

I am planning on using an 1 1/2" x 1" aluminum tube, rolled to fit, as a replacement for the floor channel at the rear of my trailer.