'Soldering' aluminium

Anyone tried **LINK**

Claims to be a 300 degree C 'solder' for ali, but I have my doubts!

What I want to do is repair a wheelchair footrest made from 2mm ali sheet for a Remap job, but I haven't the kit for welding ali. I might do better by riveting on some angle, but would welcome comments.

It's doable and there are several products on the market. It takes a bit of a knack though and I'd be inclined to solder a piece of angle into the joint as well.

For a Remap job I'd be inclined to find some small outfit locally that does aluminium welding and talk them into doing it for free. Motorbike shop would be a good start for a contact

**LINK**

Fluxes for Aluminum must be able to dissolve its oxide (Al2O3).

They are generally based on various fluorides and hexafluoroaluminates.

Perhaps the best is Caesium Hexafluoroaluminate Cs3AlF6 mixed with some Potassium Hexafluoroaluminate K3AlF6. to get eutectic mixture. These compounds are not particularly toxic or dangerous and only mildly corrosive, regardless what nonsense is written on the label. Just dont eat contents of the bottle, dont drop it to your eyes and you will be fine.

Good (and not very cheap)commercial fluxes for Aluminum will contain mixture of compounds specified above.

These fluxes are working at relatively low temperatures (400 +/- 50 *C) and are efficient.

Solder itself is Aluminum-Zinc Alloy..

With aid of these fluxes it is easy to solder together small details made of Al but also one can solder Aluminum to carbon steel (didn't test with stainless). My mom have aluminum kettle rivetted to steel handle. Rivets fallen out and item disintegrated so I have undertaken attempt to solder it together using said system. Aluminum was cleaned to metal, steel as well, both components were degreased with dichloromethane (paint strippers are often based on this solvent). Steel component was treated with 10% hydrochloric acid for few minutes, washed with deionized water, dried with blower and components immediately soldered. Gently applied propane torch is good enough. Nice metal flowing to both components can be observed. After job all was washed and cleaned.

Repaired kettle is being used for several years and I don't see any worrying sign at the joint. It takes 3 pints of water per go.

Martin

That particular product I've never used, so can't comment.

I have used a different, but similar one, which comes with a stainless wire brush and a stainless poking stick. Essentially, you de-grease the metal, wire brush it and heat it up. offer up the stick or wire "solder" till it forms a puddle of molten solder, and poke/scratch through it with the stainless wire rod to scratch through the newly formed oxide layer underneath. When you've broken through it, the molten solder wets the parent metal and lifts the remaining oxide layer so the joint becomes soldered.

It took me a few rods to practice it, and I'm well out of practice, but it does work. The parent metal broke before the joints.

I have used "Durafix" to great effect and would recommend it for dissimilar metal too (copper to aluminium, no flux needed, no problem)

You need a lot of heat, anything sub 0.7mm, and you'd probably melt it unless you've got excessive amounts of "the knack"

Edited By Russ B on 01/11/2017 03:57:59

If you're near or passing Doncaster, let me know.

Used to be a guy at exhibitions who demonstrated aluminium "soldering" using I think a butane torch, it used relatively little heat and the parent metal had to be scratched once the pool of molten solder formed to break the oxide layer and form a bond, once cooled it produced a very strong bond and the parent metal broke before the bond. The product was Swedish and not cheap but very effective, for the life of me I cannot remember the name of the product so not very helpful.

Dave

There was a Swedish bloke at Midlands MEX selling aly solder a few weeks back and some on here might have seen him at this and other events he attends. His demo's are interesting to watch and he makes it look very easy although I suspect it takes quite a bit of practise to get it "right".

His prices I thought were eye wateringly high and although tempted I kept my wallet shut.

Rik

What is this voodoo?

Dave,

It's Alutight,

https://www.youtube.com/watch?v=aiThO-UQIWE

I used it last week to weld a larger tube which I machined from solid stock into my Super 7 gear cover to accommodate the rear of it's 30.5mm capacity spindle, .

I've tried other products but this is the one I like best for Aluminium and Zinc casting repairs, there is a knack, I use a 3mm Stainless rod with a point at one end and screwdriver form at the other for breaking the oxide layer but there is no mucking about with a stainless wire brush needed, the two main things are -

(i) Enough heat to get the part to temperature and

(ii) Enough local heat sinking for smaller parts to avoid overheating on small or thin parts.

Regards,

Nick

I have used a similar product called Lumiweld if I remember correctly. It works and works well. BUT it needs some skill to perform. You have to scratch through the melted material to get rid of the oxide layer on the aluminium. A stainless rod with a point is needed. So you need 3 hands for a period. Once the "solder" takes, then there is little need for further scratching.

Beware that if there is a slope away from the weld site , then the solder very easily runs off! I tend to use a V preparation (like arc welding prep). The molten solder then will be retained.

You need to practice, most people that say that aluminium eutectic rod doesn't work, don't have much patience! It does work and is both strong and effective, but you need to practice in order to get the knack. All that has been said in previous posts should be headed, cleanliness, sufficient heat etc.

The eutectic rod is quite expensive, but that is because it is a niche market, I tried some from Ebay, which was a lot less than most, not quite as easy as Lumiweld, but not much difference overall. I would use that again for economy.

Andrew,

I'm wondering if this is just birmabright in rod form?

I remember seeing the same guy at Harrogate & Doncaster ME, looked easy enough to do but I suspect that there is a 'knack' to it as well as cleanliness, not cheap either, IIRC it was approx' £16 for 2 mtr length.

George.

I've used Bernzomatic aluminium soldering rods a fair bit for mainly sorting non structural motorcycle bits, cracked cases, filling and re drilling holes etc. It's flux coated doesn't need stainless scratching. Managed to butt solder tube to plate which took a few whacks with a lump hammer to knock it apart when I scrapped it. It's 400C melt not be confused with their aluminium brazing rods which are 700C. Used to get them from B&Q now it's fleabay.

Alutite

The rods the Swedish chap sells are very easy to use and work well. No flux required.

No knack either - he let me have ago on his stand once and I succeeded first time, I've since used it several times. The only down side is it's hard to weld both sides of a joint.

I have happily soft soldered aluminium in the past, you just need to scrape a patch, melt a pool of rosin flux over the top, scratch through the flux and it will happily let you soft solder a wire, tag or cable to it.

Neil

I live about 10 miles north of Leicester not far away we have a specialist tig welder, he will do small welding jobs for beer money.

How is he with die cast zinc alloy parts?