[bobmarkert]

I wanted to solder a wire to a piece of .020 aluminum. I did a test solder on some scrap aluminum. Scuffed up (one side on test piece) and cleaned with alcohol. I could not get the soldier to flow. Is there a trick to soldering to aluminum plate? Could it be I just need to get more heat into the aluminum or is something else going on here?
Thanks
Bob

 

[vlittle]

Aluminum is not solderable using normal techniques. You'll need to use a mechanical fastener or some fancy brazing method that I never mastered.

Vern

 

[eddieseve]

Hi Bob


You might find this helpful

http://www.instructables.com/id/How-to-weld-aluminum/

Cheers

 

[bobmarkert]

thanks

thanks, plan B

 

[DanH]

I wanted to solder a wire to a piece of .020 aluminum.

I've soldered aluminum screen into a brass shell with Harris AL500. Works very well.

http://www.harrisproductsgroup.com/en/Products/Alloys/Soldering/Lead-Free-Solders/Al-Solder-500.aspx

 

[wjb]

Soldering to aluminum with standard tin/lead solder won't work well at all. The typical way to electrically bond to aluminum is to alodine the surface and use bolt/nut and ring terminal to make a good electro-mechanical bond to the aluminum (see MIL-DTL-5541F for more detail). The alodine minimizes the possibility of aluminum corrosion between the dissimilar metals of the aluminum and ring terminal (which usually is copper with a tin or tin/lead plate)

 

[larosta]

Conductive Epoxy

YOu may want to look at an electrically conductive epoxy. Probably not a candidate for high current but a good option for shielding connections and antenna ground planes. McMaster Carr stocks it as do several of the electronics supply houses. Do a search for "electrically conductive epoxy"

It is expensive but can be a good solution to difficult problems.

Prep, prep, prep!

LOCTITE ABLESTIK 3888

 

[lr172]

They make a special solder for aluminum, but I have never been able to make it work. I believe that it won't hold the heat. AL is a bit** I have successfully stick welded it, but never solder. Brazing may work but will require a oxy acetylene torch.

Larry

 

[DaleB]

You can do it, it just takes a different technique. I've soldered a lot of wire to AL battery cases and the occasional sheet.

You need to use an iron or gun with enough wattage to heat the AL, which may be difficult due to the large mass/area that needs heating. AL conducts heat really well, meaning you're trying to solder to basically a big heat sink. Also, solder will stick to AL but not to aluminum oxide, which forms almost instantly when it's exposed to air. Clean it, scuff it, doesn't matter, by the time you get the solder to it, it's oxide coated.

The solution is to scuff the surface while it's covered from exposure to air. I have read of people using oil to coat the area to be soldered. haven't tried that, although it sounds reasonable. I have used an iron with a sharp or rough tip to melt a puddle of solder, then scrape away the area under the solder puddle. When you rub away the oxide the solder will stick. Once that happens you can get a good joint with the wire.

That said, when I need to attach a wire to a piece of sheet metal it's usually time for a ring lug, screw and a coupe of washers.

 

[JDA_BTR]

A small screw/bolt with a lug washer is the best way; Noalox between the Al and the washer will minimize corrosion - that's the ham radio way anyway.... I don't know about noalox on an airplane maybe someone can tell me.

 

[humptybump]

Dan, this looks curiously similar to Chitty Chitty Bang Bang. Are you making a flying car?

 

[DanH]

Dan, this looks curiously similar to Chitty Chitty Bang Bang. Are you making a flying car?

Believe it or not, I actually did work on a friend's flying car for a while...but the photo was a replica OX-5 radiator I did back in the late 90's for a JN-4C replica.

A Dan Simonson calendar shot, circa 2001:



http://www.amazon.com/Vintage-Airpl...r_1_16?s=books&ie=UTF8&qid=1422459991&sr=1-16

 

[Mike S]

Also, solder will stick to AL but not to aluminum oxide, which forms almost instantly when it's exposed to air. Clean it, scuff it, doesn't matter, by the time you get the solder to it, it's oxide coated.

Yep, remember my dad telling/showing me this half a century or more ago.

The solution is to scuff the surface while it's covered from exposure to air. -------- When you rub away the oxide the solder will stick. Once that happens you can get a good joint with the wire.

What my dad did was to make a puddle of flux (paste style flux) where he wanted to solder, then use a small steel brush to burnish the alum under the puddle, then he would solder the alum while still covered with the liquified flux.

 

[Mike S]

the photo was a replica OX-5 radiator I did back in the late 90's for a JN-4C replica.

A Dan Simonson calendar shot, circa 2001:

OK, Dan---gonna out you on this. I know there is more to the story.........

 

[rv7charlie]

I built an aluminum intake manifold (alt engine) out of 1/4" plate, .032 wall tubing, and AL sheet and brazed it with rod similar to what DanH linked. The stuff I used can be flowed with a propane torch; IIRC, melt temp is around 750-800 degrees, which is well under the melt temp of aluminum. Cleanliness (and a stainless steel brush) are beyond godliness when trying to make it work, but the joints are pretty strong (metal fails 1st). I'd never do it for structural parts, but it seemed to work fine for the manifold.

Google 'aluminum brazing rod'; the major welding suppliers all sell products that will work. Most are intended to join aluminum and other non-ferrous metals to themselves and each other.

Charlie

 

[DanH]

I built an aluminum intake manifold (alt engine) out of 1/4" plate, .032 wall tubing, and AL sheet and brazed it with rod similar to what DanH linked. The stuff I used can be flowed with a propane torch; IIRC, melt temp is around 750-800 degrees,

Harris AL500 is nothing like the aluminum brazing rods. You just clean with a stainless brush, flux it immediately with the Harris aluminum flux, and solder like any other solder. The 500 in the name means a 500F working temperature; it is liquid at 482F per spec.

That radiator shell was made in four pieces, with silver-brazed butt joints at all four corners. Silver brazes are ballpark 1200-1400F. A true low-temp solder was desired for the screen, in order to have no risk of disturbing the braze joints.

 

[rv7charlie]

Harris AL500 is nothing like the aluminum brazing rods. You just clean with a stainless brush, flux it immediately with the Harris aluminum flux, and solder like any other solder. The 500 in the name means a 500F working temperature; it is liquid at 482F per spec.
.

Sorry; I should have looked closer at the Harris page before posting. Wish I'd known about it prior to using the stuff I did; the lower temp would have made my work a bit easier.

Charlie

 

[wjb]

What my dad did was to make a puddle of flux (paste style flux) where he wanted to solder, then use a small steel brush to burnish the alum under the puddle, then he would solder the alum while still covered with the liquified flux.

Sounds like an alternate to TIG/MIG welding ... keep the oxygen out so the surface doesn't oxidize before you can bond to it.

Practically, though, a better connection would be an alodined surface (or equivalent) with a nut+bolt+ring terminal, torqued down. Mechanically, that would be more reliable than a wire soldered to the surface. This comment would apply to soldering to copper as well. Good electrically, not so great mechanically.