Brazing copper to aluminum?

[Strida]

I've never tried anything but copper/copper or copper/brass with my phase change system, but I have a spare compressor I'm looking to add a schraeder valve to in order to make a vacuum pump, but the compressor has aluminum pipes instead of copper.

Is it still possible to braze copper to aluminum? I know when welding, getting aluminum to stick is near impossible, just wasn't sure if it was the same with brazing.

Thanks for the info,
Derek.

[LabRat23]

It will never happen. The alluminum burns under the flame that is required to braze copper. I have tried soft soldering alluminum too, and that is darn near impossible.

[jinu117]

You need aluminum soldering rods, etc and probably want to stick to propane torch... :p
But that aside, the metal on compressor most likely is steel. (or stainless steel). You need to use at least 15% silver solder or 45% silver solder to braze it.

[Time4aMassiveOC]

i heard that copper and aluminum was nearly imposible to get to stick together but had to use something like a transition metal. maybe like what jinu stated above

[jinu117]

(It isn't like they weren't able to to solder copper aluminum heatsinks before :P) But I honestly can't think of compressor made of aluminum shell. Would be kind of neat but when we talk about 400PSI at least... it's tad harder.

[EvilT]

u can just join the 2 pipes together with an hard od plastic pipe or use jb weild and if everything else fails use duck tape :D

[greenmaji]

when welding aluminum most people just go ahead and use a TIG welder..
I have a feeling your not dealing with aluminum though.. I think jinu is right its most likely steel of some sort. in wich case the prodomataly silver rods are used for brazing a diffent metal to it (like copper).

[Susquehannock]

Brazing & welding aluminum to copper is difficult, but not impossible. The main problem is
the difference in melting temps, & subsequent brittleness of the joint. And of course you must
keep the aluminum extremely clean.

You can use the same fillers & flux (non-corrosive) that you would for joining
aluminum. Silver alloy filler can be used provided the heating & cooling are rapid
- to minimize diffusion.
Pre-tinning the copper with the filler can help since it improves wetting, & permits a
shorter brazing time & lower temp.

[Strida]

Alright the compressor is in fact made out of steel, but the aluminum pipes going to and from it aren't coming off. I have some spare JB Weld so I think I'll probably just use it to connect the copper pipe to the aluminum one coming out of the compressor. It's just being used for a vacuum pump anyways.

[greenmaji]

JB weld is epoxy.. I dont see how in the world that would hold! :(
I thought EvilT was joking.. but it looks like you might have took the advice.. :(

are you positive it has aluminum pipes? I would bet there steel.. just try to braze them..

[EvilT]

JB weld is epoxy.. I dont see how in the world that would hold! :(
I thought EvilT was joking.. but it looks like you might have took the advice.. :(

are you positive it has aluminum pipes? I would bet there steel.. just try to braze them..
srry i was half asleep, but jb weld is very strong bc weve used it on hydralic lines on a trator and its held for almost 3yrs now

[Strida]

I am completely positive the lines are aluminum. It's from a super-cheap air conditioner.

Anyways, yea JB Weld should hold for just the vacuum pump I think. I know a friend of mine has used it to seal up a crack in his engine block before and it has held 100%.

[Susquehannock]

That's true. Over the years I have seen JB Weld used for many things you would not expect.
Hope it works out for the best Strida.

[greenmaji]

ok ok.. hope it works for you then.. good luck.. :D

[RoadWarrior]

JB weld works better than normal epoxy for stuff like this because it has a conductive filler, that means it can expand and contract more evenly than regular epoxy and not just crack off the metal.

Anyhoo, I've got some stuff here that claims to be perfect for this, meant for aluminum radiators, HVAC piping etc, aluminum to aluminum and aluminum to copper. It's called "Kool-it" brand "Solder-it" Aluminum solder paste, comes in a 7.1 gram syringe packed on a card. Needs 395F to flow, tensile strength is claimed to be 28,000 PSI. Haven't actually tried it myself yet, just picked some up when it was on sale once cna caught my eye, in case I ever needed it.

[EvilT]

make sure u ruf it up with sand paper and clean it so it will stick/bond good :)

[Strida]

Well I guess all of this discussion was without a point for me. I got everything JB-Welded up and went to plug in the compressor and it doesn't work. Well, it worked a year ago but something must have happened to it in that time.

=(

[RoadWarrior]

Smack it with a 2x4 :D