We sold a job with some 1/8" aluminum pour stop and this gets a handrail attached to it. The design drawings spell out a bent pour stop using 1/8" aluminum with an aluminum shoe molding. I think someone for got to do their homework, but none the less we have to provide this material in some fashion. I was wondering about attaching this "aluminum" pour stop to our "steel" beam. Can't weld, so we were thinking of bolting, but I was wondering about the dissimilar metal corrosion between the two.
Do we need a rubber gasket or can we paint the flange of the beam with something to stop the reaction? Ideas or suggestions welcomed. I need to submit something to the engineer of record. Personally I think 1/8" aluminum is going to be very flemsy to attach a hand rail to and we may have problems bending it 90* without cracking it.
John Wright
John,
Check out this link that mentions using a specially modified GMAW process with 100% argon:
http://www.thefabricator.com/Articles/Fabricating_Article.cfm?ID=676
Also, in Metals and Their Weldability,Vol. 4 of The Welding Handbook, there are indications that aluminum may be joined to steel by soldering, explosion welding, friction welding, ultrasonic welding, and adhesive bonding.
Is the handrail you're attaching also aluminum? If not, have you looked into using galvanized or stainless pour stops? Then, welding wouldn't be as much of a problem.
Hi John,
A few years ago I was working in a shipyard that made and refurbished mobile offshore drilling rigs. These rigs hade a steel barge type body and an aluminum superstructure. On the older rigs, the superstructure was attached to the deck with a 1" x 4" aluminum angle bolted to a steel T beam and a 3/4" hard rubber gasket inbetween.
Every time we refurbished a rig, we had to replace both the steel T beam and the bottom foot of the superstructure bulkheads due to the corrosion. We replaced with explosion bonded transfer strip and didn't have to worry about it anymore.
Anyway, my point is that with this type of connection, even though you electrically isolate with a gasket, dissimilar metal corrosion problems still occur around the bolts.
Good Luck!
Tim
I think I would put a flat plate on the bottom of the handrail posts to bolt it to the beam and drill the bolt holes through the flat plate and pour stop so it is sandwiched. I agree that it is not thick enough to keep the handrail from bending it.
Bump
"Do we need a rubber gasket or can we paint the flange of the beam with something to stop the reaction?"
If you use a steel handrail and bolts and sandwich the aluminum pour stop between the flange of the handrail and the beam, then I see no need for a rubber gasket. You should coat the steel as you normally would prior to bolting them together.
Thanks Marty,
I was just concerned whether to mix the two without something inbetween or not. We'll coat the top flange of the beam with something and bolt the aluminum bent plate on. The handrail is currently being attached to something else.
John Wright
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