How to solder aluminium rods?

[gil]

Hello,

I am using 4mm aluminum rods for my UHF quad build and need to solder them for electrical continuity. A French site I found suggests using vaseline as flux so I tried that with my soldering iron set to 450C... To no avail. Now I have a whole tube of vaseline I don't know what to do with :o Does anyone know how to solder aluminum or if it is even possible? Should I try to slightly melt the rods with a torch? Brazing? Thanks...

Gil.

[Quietguy]

It is very difficult to solder aluminum and you can't really "slightly melt" it because aluminum does the transition from solid to liquid very quickly and you end up with a puddle.  The best way is welding with a shielding gas because aluminum quickly oxidizes.  I assume you are trying to butt the ends of the rectangles together and make them electrically continuous.  There is an oxidation inhibitor paste designed for making aluminum to copper joints in electrical wiring.  Maybe you could clean the oxidation off the rod ends, apply the paste, and make a saddle splice out of copper spanning the joint.  The cleanest solution is to find a friendly welding shop and have the ends welded.

Wally

[gil]

I assume you are trying to butt the ends of the rectangles together and make them electrically continuous.

Exactly.

There is an oxidation inhibitor paste designed for making aluminum to copper joints in electrical wiring.

That would be my ticket since vaseline did not work. I will try one more time though after cleaning the junction. Thank you Wally.

Gil.

[KK0G]

I'm just going to ignore the Vaseline comment 8) .


I've attempted soldering aluminum and it's an exercise in futility. I ended up using a mechanical connection.

[Quietguy]

I ended up using a mechanical connection.

Yes - I should have made my comment clear that the oxidation inhibitor paste was for mechanical connections between aluminum and copper, not soldering.  Copper and aluminum mechanical connections aren't reliable because of oxidation.  That was a major problem in the early days of aluminum house wiring connected to copper terminals on receptacles and switches.  I was suggesting using the paste along with a copper saddle straddling the joint.

Sorry if I confused the issue...
Wally

[cockpitbob]

If you have the gear, you can weld aluminum, but it takes experience and just the right gear.  One part of the skill is aluminum melts before it gets red hot.  You can't tell the temperature from the color.

Standard solder won't stick to aluminum no matter what you do.
OTOH, there are several aluminum brazing products out there that work with a standard propane torch.  Basically they are a zinc alloy and flux.  I've actually never tried it, but those products have been on the market for decades so they must work.  I've also seen a salesman demo where he brazed the butts of 2 coke cans together.  All he did for prep was scrub with a stainless brush.

The big problem with aluminum is it quickly develops a thin oxide.  For what little aluminum welding I've done, I scrub the area with a stainless wire brush (sand paper will work too) then clean it with rubbing alcohol, then I get the flux on it right away.  The flux in the brazing kits may be aggressive enough to eat right though the oxide.

[gil]

Thanks Bob, I'll look for that. BTW I know aluminum boats have sunk because someone dropped a copper penny in the bilge...

Gil

[cockpitbob]

Thanks Bob, I'll look for that. BTW I know aluminum boats have sunk because someone dropped a copper penny in the bilge...

Gil

Dissimilar metal corrosion?

[gil]

Dissimilar metal corrosion?

Yes, aggravated and sped up by stray currents in harbors. The worst story I read about however was that of a boat builder who elected to build his boat out of copper-nickel, undoubtedly the best hull building material since it can be left unpainted, does not rust and repels barnacles. It costs more than ten times as much as steel. Unfortunately the builder chose to use stainless steel frames inside the boat. It was all scrap within four months. Same with people building metal boats and wiring the negative of the battery and engine to the hull... Big no-no if you want to keep your boat afloat.

Gil.

[Prepper_Tux]

https://youtu.be/jtvOkI_pvMI

[gil]

Thanks. I tried that... Didn't work, but I think the brazing rods were crap.

Gil.