Soldering Aluminium....

[nammie]

.... is it possible?

A basic question perhaps but googling doesn't seem to answer it. I have a source of cheap (free?) aluminium sheet and would like to use it to make 'frames' for some polymer clay (yes, we're not talking fine jewellery/stone setting here, look away now if you're easily offended). Ideally I'd like to be able to solder the joints but before I start I'd like to check that I haven't set myself an impossible task. I seem to remember from GCSE Chemistry that Aluminium oxidises easily and the surface is pretty much Aluminium Oxide...Or I could be over thinking and should just wave a torch at it and get on it with it...

Nammie

[mizgeorge]

You can't braze aluminium, but it's pretty easy to pierce if you can make that work for your design?

Alternatively, you can use soft solder (with an iron), but you'd have to make the raised joints part of the design as it's not practical to remove all the excess.

[Kwant]

I'd be tempted to have a go at casting the stuff, it melts at quite a low temperature and as it is cheap, there is a slap dash technique the Chinese use where they pour the molten metal into their moulds and slap a board on top real quick to press it in. There is a lot of overspill which is very easily cut off. Your mould could be cut out of soft wood, blackened with a candle and ......... well there you go ;0)

[josef1]

Its difficut to join aluminium as its such a good conductor of heat, it is possible with the correct flux a good tourch and a filler rod but its a skilled job.As above I would use a mechanical way ( screws,binding,threadings etc) if it was possible

[nammie]

Thank you all for the considered opinions. I think I had a bad case of 'its free, I MUST make it work'. I've given some serious thought to mechanical joining as I was driving today and think I could revise the plan in that direction. Failing that, I'll buy some brass or copper sheet and do it properly.

Kwant - Thank you for the casting thoughts but, call me chicken, I think I'll pass for now. I have memories of my grandfather melting down lead in an old ladle over an open fire and casting it in aluminium food trays. I also have memories of of Gran shouting about the spills on the carpet. I'm not sure this is a process I should undertake in my kitchen, let alone my rented kitchen.

Nammie

[lambchop]

Hi Nammie
Yeah soldering Aluminium is really difficult, the oxide you mention that forms on the surface of the aluminium makes this a pig of a job unless you use some really vicious fluxes like Josef mentions and of course the correct solder. It looks like a case of cutting/filing to your desired shape..or along the 'casting' method mentioned I use a low melting temperature alloy 'cerrobend' (cadmium, bismuth, lead- so don't breathe it in!) It melts around 70degrees or something close, a cup of hot water melts it so is safer than regular casting. If you struggle to find it, PM me and I'll send you a bit to play with

[nammie]

Thanks Lambchop. I had a bit of an rethink of the plan and realised I was trying to force a method on to a material. What I should have been doing was planning to use the material in a way that it works best. What I'm trying to say is that I believe good design is using the properties of the material to the best effect not forcing it into a design its not suited for. Sounds a bit pretentious and I'm not guilty of 'good design' very often but I have vast personal experience of bad design :-)

Now, having spent several nights lying awake thinking of aluminium sheet, my cheap source of it has gone camping in Devon! With any luck the weather will send him home early as I'm getting twitchy now.....

Nammie

[mizgeorge]

If you're looking to make frames with the sheet, have you considered cutting several layers and riveting them together to get the depth you're looking for? Cold connection is, for me, always the way to go with aluminium, with the advantage that a regular riveting tool does the job beautifully!

[Dennis]

Following on from what the George has said, you can easily make you own rivets from aluminium or copper rod or tube.
If none of the above grabs you then any steel or stainless steel screw, forced into a slightly undersized hole will do the trick. Specialist such as Clerkenwell Screws do some classy ones.

Dennis.