Welding/soldering SS or brass to Al, help please.

[mental4astro (Alexander)]

Hi all,

I've got a project going where it would be advantageous to either weld or solder stainless steel or brass/bronze to Al. I know welding Al requires Tig, and soldering Al is an art form too, and SS ain't no walk in the park either. But, brass and bronze I have at home, and would like to know if these copper based alloys can be welded/soldered successfully to Al, and without major galvanic problems in the long term.

I'm also open to other ways of joining them, like cold riveting, glueing, etc. Brass and the bronze I have is particularly malleable, and I've cold riveted this stuff successfully before.

The project is a secondary mirror holder, so the joints are small, and there really are no significant stresses that the joints will be subjected to. The number of joints are as few as 2, and as many as 4. And the temperature range the finished piece will be subjected can go from warm to sub zero as can be experienced with astronomy here in Oz.

Any help would be appreciated.

Mental.

[LewisM]

No idea, but many aircraft manufacturers glue and rivet aluminium sheets together, and they hold up rather well

McDonnell Douglas was a major user of glue bonded aluminium alloys. I presume they still do, even under the Boeing name.

I USED to know the name of the glue they used - maybe Col may know?

[cfranks (Charles)]

Try http://muggyweld.com/

I bought their sample pack many years ago but, typical me, never tried it. One of the many things in my cupboards that 'Might come in handy one day'!

Charles

[Barrykgerdes]

Forget about welding/soldering of these dissimilar metals. While there are probably ways to do it, it certainly won't be easy.

Before aluminium welding became a breeze a substance with a commercial name of Araldite for joining aluminium was developed. However I think super glue may be better now.

Barry

[wasyoungonce (Brendan)]

I tried Alumaloy Aluminium rods and a MAP brazing torch ...it works doing aluminium ok, small jobs. I was surprised! Just need to ensure you clean the surface with a stainless brush and the oxidisation surface of the join while molten with stainless wire rod.

It does work but I don't know how good with differing metals.

TIG should work...just fusing the material no filler! That said...TIG fusing point (welding settings) for one metal like brass will be very different to aluminium. Probably end up turning one metal to oxide ...?

Maybe spot weld?

[Astro_Bot]

As Barry said, welding dissimilar metals isn't easy. The simple advice is to avoid it if possible, and invest in cathodic protection if you do (if I recall my theory correctly).

I know some structures use steel as a lower level and aluminium as an upper level. Unfortunately, I don't know how they're attached.

[Baddad (Marty)]

Hi Alex,

Forget welding. Too difficult. Soldering is okay. Use the special flux. I have forgotten the names but I have soldered SS, Al and copper alloys successfully.

Super glue becomes brittle and releases after time.
Araldite, I don't know about. It may not be effective on metals.

Rivets work. In aircraft they use titanium rivets.
Also a special two pack glue for metals is available. It is expensive but I have used it to seal up holes on stainless 7 years ago and it is still holding.
An excellent glue. I acquired info from a guy who owned a SS and Al welding shop.

Hope this helps.

[LewisM]

Best epoxy glue - JB Weld, especially the marine version. I managed to but join 2 pieces of plastic, that endured HIGH use and FLEW for 3 years before it broke - in a different spot! The stuff is incredible, but make sure the surface prep is flawless.

I accidentally dropped a glob on tiles without knowing. It's still there, as I fear if I mechanically chip it off, it'll take tile with it!

[Kunama]

Brass and aluminium are too far apart in their anodic index values so you will get galvanic corrosion just depends what environment they are in, any immersion esp. saline environments will accelerate the galv. corrosion.

Stainless steel (-.40V) too is quite far from aluminium (-.90V) Thats why aluminium boats with stainless props have zinc sacrificial anodes.

I too would suggest a chemical bonding agent that effectively forms a barrier between the 2 dissimilar metals.

Edit: Ideally you want the metals to have a difference of less than 0.25V in the anodic index (Wikipedia has a table)

[AstralTraveller (David)]

I know Dad used to silver solder almost anything to anything but I'm not sure I ever saw him do Al. Looking around there appears to be fluxes out there that will do the job.

http://www.cupalloys.co.uk/joining-a...m-c100014.html
http://www.youtube.com/watch?v=UGsQP-wX1lI
http://www.hobartwelders.com/weldtal...p/t-31260.html

[bloodhound31]

Join metalmeet forums.

[louie_the_fly (Stew)]

Sikaflex is a great product It's a black polyurethane based compound used in lots of manufacturing industries these days. Auto industry have reduced the requirement for spot welds by using compounds like this. It's what your windscreen is glued in with. It sticks most everything to everything, except polyethylene from my experience. Comes in a tube like silicon. Not sure if you can get a toothpaste size tube. Once opened it doesn't have a great shelf life though. You can get it at Bunnings, amongst other places. Just don't get it on your blanket... Cos it sticks like you know what.

Stew

[ZeroID (Brent)]

JB Weld or rivetting, preparation is essential for JB Weld. I've used Araldite and it works but the temp variations and metal expansion eventually breaks it. Unless you drill wee holes and use those to key the two parts together. In which case you may has well rivet it.
What about small self tapping countersunk head screws ? I use those regularly in Steam Punk builds.

[mental4astro (Alexander)]

Thanks everyone for the information and your experiences. I'll need to think about the various options that have been suggested and how to best go about this project.

I'm still happy to read more of folks' experiences though,

[OzEclipse (Joe Cali)]

Hi Mental

I've joined aluminium using a special eutectic flux that allow the use of a gas torch to join two pieces of Aluminium. Put the flux on the surfaces heat up and carefully join when the ally melts. I was making aluminium wire seals for vacuum systems. The trick is, you need to use pure aluminium. The other problem is that Aluminium conducts heat away very quickly. Dreadful job. It's hard enough in thin 0.5mm wire to get the heat in to melt the wire let alone some big thick extrusion. The alloys used in the billets they feed into extrusion dies don't weld nearly as well. I've gone back to using 99.99% gold wire, more expensive but much easier to weld

Some eutectic fluxes allow dissimilar metals to be joined. PM me a description of exactly what you want to do including the alloy numbers and thicknesses and strength required. If I don't know, I can find out from a close friend who runs a high tech engineering workshop what if anything you can use to do the job.

cheers

Joe

[OzEclipse (Joe Cali)]

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