| The Shop > Metal Stuff |
| Telling metals apart for casting. |
| (1/4) > >> |
| S. Heslop:
I've been searching around for a while on this topic and haven't found anything satisfactory. I've got several aluminium castings i've been saving to melt at some point, but now i'm unsure if it really is all aluminium or not since one piece (from a washing machine drum) feels a bit heavy. I feel a bit dopey asking this question but is there an easy way to check? I could probably do it by density but I want to avoid getting the metal wet if i'm going to be melting it. |
| mattinker:
Hi, if a greyish metal feels "a bit heavy" it's probably of the ZA family of Zinc alloys. Pure Al has a density of 2.7, for every litre of metal, it weighs 2.7Kgs. If you measure the volume of water displaced by the metal when it is submerged, and weigh the metal, if it is a Zinc based alloy it will weigh more than 2.7Kgs per litre. I do this if I'm not sure, A bowl of water, full to the brim in another bowl, emerge the metal in the water, the water that spills into the second bowl is the same volume as the metal. Measure the volume of the water either with a measuring jug or by weighing the water. Water has a density of 1,0 so 1 Kg of water equals 1litre. Weigh the metal, if the weight of the metal is 2.7 times the weight of water, it's Al! Zinc has a density of 7.134, so it's nearly three times heavier per litre than Al. The Zinc alloys aren't very popular as they are often badly used they are difficult to weld and are brittle. The good side, they have good vibration damping characteristics (close to cast iron), Cast very well, machine beautifully and make very good bearing material for steel shafts. The ZA Zinc alloys can be cast at much lower temperatures than Al, with a melting point of around 450°C. The thing to avoid with Zinc is overheating it. Over 700°C, it boils and gives of white smoke (Zinc vapour) that can give you (fume fever) flu like symptoms! Don't breath it! I hope that helps! Regards, Matthew |
| tom osselton:
I read on one site to use vineger as it will bubble on the magnisium but not on aluminum although I haven't tested it out to make sure. |
| RussellT:
I saw this http://forum.caswellplating.com/plating-pot-metal/9034-how-can-you-tell-pot-pot-metal.html I've got as far as buying some hydrochloric acid - freely available in French supermarkets - but I haven't tested it - or considered the chemeistry. Russell |
| S. Heslop:
--- Quote from: RussellT on November 09, 2013, 06:00:44 AM ---I saw this http://forum.caswellplating.com/plating-pot-metal/9034-how-can-you-tell-pot-pot-metal.html I've got as far as buying some hydrochloric acid - freely available in French supermarkets - but I haven't tested it - or considered the chemeistry. Russell --- End quote --- I did see that and wasn't too convinced, but i've been planning to try it out anyways next time i'm in the lab. I might try the density thing too at some point, I figured it'd be a good way to do it but I was hoping there was a less laborous solution. Thanks for the replies though. |
| Navigation |
| Message Index |
| Next page |