Anodised aluminium

**Sean2638** · 07-06-2020, 05:21 PM

Looking for some advice.

Im building my own foundry and I have a load of old aluminium heat sinks laying about that I thought I could melt down instead of trashing.

Does the fact that the aluminium is anodised cause any problems?

Thanks

**scrapman1077** · 07-06-2020, 09:36 PM

No, anodize is a very thin layer of aluminum oxide, it will float to the top.

**Sean2638** · 07-07-2020, 02:43 AM

Great thanks.

Would the anodised layer stay in one piece that I could easily pick out of the molten aluminium?

**WhiteSquirrel** · 07-07-2020, 08:36 AM

Just need a skimmer and it'll be easy to skim out with a layer of slag. I keep all the slag and do a quick remelt every now and then to recover as much Al as possible.

Once it's cold, that layer is easy to break off of the remelt slag by hand, and you can toss that dross then.

**Sean2638** · 07-07-2020, 09:18 AM

Ok great.

I’ve only seen small foundries.

I want to build an electric one 50cm x 50cm x 50cm

If I use enough insulation do you think it’s still possible to have one this size?

**WhiteSquirrel** · 07-07-2020, 12:22 PM

Originally Posted by Sean2638

Ok great.

I’ve only seen small foundries.

I want to build an electric one 50cm x 50cm x 50cm

If I use enough insulation do you think it’s still possible to have one this size?

Heck. YES!

Outer layer is 19 inches across, with my large burner this thing melts alum faster than I can keep up with feeding the crucible. Word of caution though : the extra fire pot and air causes some increased scaling rate using steel crucibles, so I would suggest getting a large graphite one.

**Sean2638** · 07-07-2020, 01:17 PM

If I was building it with electric rather than a burner how much insulation do you reckon I’d need?

I was looking at graphite anyway. Didn’t think steel would be much use if I do manage to make an amazing foundry as the steel might melt haha

**WhiteSquirrel** · 07-07-2020, 02:20 PM

I always use 2 inch refractory wool since it keeps its shape nice, but 1 inch would be good enough. Slap a layer or two of sealant/coating on that, and you should be good to melt anything up to 1200C.

There are some awesome electric furnace videos out there, with VOG on youtube having one of the neatest setups I've seen. I recommend playing around around with whatever you have laying around until you have something that works the way you want it, then spent the time and money to make that setup into something a little more permanent.

**Sean2638** · 07-07-2020, 02:51 PM

I’ve dug a whole in the ground outside. It’s solid clay. I’m tempted to put groves around it, wedge in the electric heating element and use insulation as a lid.

Do you reckon the clay earth would be a good insulator?

**WhiteSquirrel** · 07-07-2020, 04:20 PM

Not a good insulator (by today's standards), but it'll do the trick - specially just for Alum. They used to melt all kinds of metal in holes in the ground back when my dad was chasing down mammoths, might just take a little bit longer. I still use my home made charcoal to melt 75% of my Alum, just like those good ol days :P