Aluminum to Steel Connection
Aluminum to Steel Connection
(OP)
I was wondering if anyone knows about connecting steel and aluminum. I want to rivet an aluminum shell to some steel studs. According to this post http://revobiz.dyndns.org/group/seaint/2001a/msg01557.html connecting aluminum and steel is a big No No. I'm thinking that it would be possible to put a rubber strip or something along the stud, but it would be preferred if we didn't have to do anything like that. If we have to install a separation between the steel stud and the aluminum shell, then how do we connect the two? It wouldn't be possible to use aluminum rivets if the two metals are not compatible. Any insight on this situation would be greatly appreciated.
Thanks,
Mike
Thanks,
Mike
RE: Aluminum to Steel Connection
RE: Aluminum to Steel Connection
Is it also true that if the steel studs are hot-dip galvanized that you don't need to separate the two materials with the neoprene or rubber gaskets?
RE: Aluminum to Steel Connection
But just a small flaw in the galvanizing or the paint would initiate the reaction.
RE: Aluminum to Steel Connection
I have connected steel and aluminium together using threaded fasteners however I isolated them by using nylon spacers and nylon sleeves in the bolt holes to stop the bolts touching the aluminium.
regards desertfox
RE: Aluminum to Steel Connection
You can use tape as a seperator. Fiberglass works well, even packing tape works it you have nothing else. Just make sure steel is clean and then primed, then apply tape over studs. Just make that it does not store water. If you want to install Al rivets you can prime the steel then apply primer to holes then install rivets wet (dipped in primer). Then prime the bucked end. Use zinc-chromate primer.
Cad or zinc plated hardware will also work. The following site gives more detail.
http://assist.daps.dla.mil/docimages/0000/32/77/36032.PD5
RE: Aluminum to Steel Connection
The "Big SUV" of the private aircraft set - also known as the Helio Courier, has a cromoly tube frame aft and an aluminum semi-monocot frame up front. Molten aluminum is sprayed on the cromoly frame to allow for connection of the aluminum portion of the airframe while still isolating out any electolyte that could cause galvanic corrosion.
--
Joseph K. Mooney
Director, Airframe Structures - FAA DER
Delta Engineering Corporation
RE: Aluminum to Steel Connection
RE: Aluminum to Steel Connection
It doesn't solve the problem, but it may help. There still exists the problem of areas of the aluminium part that aren't covered by aluminium oxide, either from lack of original coating (sharp edges, etc.), or due to coating damage.
Regards,
Cory
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: Aluminum to Steel Connection
http://www.alu-info.dk/Html/alulib/modul/A00175.htm
RE: Aluminum to Steel Connection
Interesting subject. We have an overhead conveyor system with an aluminum rail. We also used to use an aluminum splice plate at the rail splices but were plagued with the plates cracking. We started using steel splice plates which are painted. There are 4 stainles steel fasteners on each side if the joint but these are not separated from the aluminum in the holes. Does anyone see a potential problem with this?
Thanks for any help in advance.
RE: Aluminum to Steel Connection
Regards,
Cory
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: Aluminum to Steel Connection
In this case it would probably involve bonding an aluminum and steel plate, then attaching the fasteners to the steel portion. The aluminum still has to be protected from corrosion.
Tony Holt, P.E.
Machine Development Co.
RE: Aluminum to Steel Connection
RE: Aluminum to Steel Connection
RE: Aluminum to Steel Connection
Some years ago I read an article about a special weldable alloy that solved this mounting problem. The alloy, in a rectangular shape 1/2" x 3" was tig welded to the house base flange. After the house was set in position the exposed alloy was welded to the deck. The problem is I cannot remember the periodical name containing this article. It was a Marine Industry periodical. Any answers?
RE: Aluminum to Steel Connection
RE: Aluminum to Steel Connection
RE: Aluminum to Steel Connection
Separate the steel and the aluminum. Painting each side of joint before joining will work. Sealant is better. Sealants or paints with a corrosion inhibitor in it work better than those without. Gasketing material would also work for separating the steel and aluminum.
Anodizing the aluminum first will help, but the anodize is too thin to work by itself completely. It gets scratches.
RE: Aluminum to Steel Connection
I read, on the Internet, that if difference between Anodic Index numbers is more than 0.15 V, than the galvanic corrosion does occur. According to the same source:
Anodic Index for chromium plated surfaces is 0.60, for Aluminum other than 2000 Series – 0.90, for plain carbon and low alloy steel – 0.85.
So, (my second question) it appears that contact between plain carbon steel and aluminum will not cause galvanic corrosion. Is it correct?
Thank you.
RE: Aluminum to Steel Connection
There is a possibility of corrosion (general and galvanic) for steel plated with zinc + chromate conversion coating in contact with aluminium alloys. The zinc coating is practically worthless in harsh environments.
Regards,
Cory
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: Aluminum to Steel Connection
Thank you for the assistance.
However, how to relate your first answer with the Anodic Index rule of 0.15V or less for the galvanic corrosion to do not occur? Again, low allow steel - 0.85, aluminum - 0.90.
What coating is suitable for the marine environment?
Thank you, again.