soldering aluminum?

[varmint]

Here's an unusual problem: I am installing solar heating in my shop- two big flat plate collectors, circulating oil via a pump, heating via a small oil cooler with a fan behind it. I bought what seemed to be the perfect cooler thru eBay- an Earl's NASCAR flat plate oil cooler, cost $400+ new- used but said to not leak. When I finally got the AN hoses to hook it up to some air pressure under water, guess what? The leak is small, just where the AN fitting is brazed to the top of the cooler. Since these units are factory furnace brazed under computer control, fixing them isn't easy. Earl's suggests an industrial epoxy (?) which doesn't sound good to me- I don't want to go out some day and find 2 gallons of solar oil on the floor. I am wondering if anyone has ever used aluminum solder. I think it would melt at a lower temp. than the brazing, so maybe, if I am really careful with my heat... looks like a natural place to puddle a little solder. Otherwise, I have some recycling material.

 

[KML]

I've used this and had decent results. He calls it "welding" but seems more like soldering to me. It worked for me repairing a cast aluminum part that had spider web cracks in it when silver solder didn't. His marketing comes off a bit like snake oil but the products do what he says after a little learning curve. I'd practice on something else first and CLEAN EVERYTHING! After you get the hang of it it flows out like silver soldering copper, getting into all of the cracks and joints, just at a lower temp. (350 deg F). He has another product that melts at 600 deg also it seemed to work O.K. but I haven't actually repaired anything with it just played around so I can't say it "works".

Hope it helps.

Muggy weld

http://www.muggyweld.com/1aluminum.html

 

[AlanB]

If I understand the scenario, the leak is right where the fitting is brazed on?

So, in that area, you have the aluminum base for the radiator, the aluminum fitting and the brazing material that they brazed it together with?

Assuming that, I would not want to add another material into the mix. Often times, it is hard to sort out what is what and those things turn into a mess.

My first choice would be to call back earls, and ask if you could get a little of the weld material that they use, and then apply that with a TIG and it would be a sound repair.

Second choice, if there is a little bubble of material there, you can sometimes chase it across with a TIG and seal the hole.

Third choice, I would hazard a guess that it is Silicone Bronze, and get someone with a tig to drop a drop of silicone bronze on the top and seal up the hole.

I would be skeptical of the solders and the adhesives but that is me.

Hope it works, if you need a stick of silicone bronze let me know I keep about 10 lbs usually.

If you look for a thread I did that said interesting welding (kind of) you will see where I talked about a similar process.

 

[3RRL]

Looks like the product KLM suggested is a pretty good idea.
The problem I can see trying to use a solder for a crack repair on aluminum is that yes it melts at a low temperature, but you can't get the parent material hot enough for it to bond properly. The oil cooler is an example in that link KLM shared, where the heat is dissipated rapidly. Sounds like I would give his product a try.
Otherwise, I would braze it.

 

[Soundguy]

I have soldered stuff to aluminum heat sinks.. it ain't easy.. but it is doable.. clean the surfacs.. a lil super fine sand paper helps.. lots of flux too.. I'd use silver solder.. or those alum-alloy rods and attack it with mapp or propane hand torch.. once it gets to a certain point that the solder will stickto the aluminum.. you got it made.. usually just outside the crown of the flame.. deffinately not as easy as sweat soldering copper.. etc..

soundguy

 

[varmint]

FWIW, I did talk to Earl's, and they told me that since this thing is made from a quadzillion parts, all furnace brazed at one time, if I heat it up enough enough one place to melt the brazing then I will get problems in 4 other places. Much of this thing is inaccessible, so there you go. The leak is where a machined fitting was brazed to a plate, or sheet of alum. with who knows just what underneath... so I am leery of too much heat. Earl's said you can't weld these things without disaster. If I could just heat the fitting until solder would flow, at a lower temp. than the brazing material, I should be okay. This will be a low pressure system- 10 lbs or so, and temps under 250, so maybe...?

 

[skipro3]

At 350 degrees, I'd just solder it up, then toss it in the oven to make sure the surrounding metal got that warm to make a good flow. None of the other brazed joints should be affected at 350 I would think....

 

[Soundguy]

I agree.. solder should melt WAY before any brazing materials..

soundguy

 

[mrutkaus]

you can get these aluminum welding sticks on ebay and other places, which you use with a MAPP torch to weld aluminum. they work

mike

 

[Soundguy]

Alumaloy is the one that I mentioned.. but I have seen them all over.. even fleay markets.. I saw a guy solder up a hole in the bottom of a soda can with one of them..

soundguy