Is there an easy way to tell the difference between aluminum and magnesium? I TIG weld lots of aluminum castings, and have been given a few magnesium castings as well. In those situations, I was told beforehand that the casting were magnesium, but lots of people bring me castings without knowing what they are. Thanks!
Have welded Magnesium and it requires a special Mag. rod , I used to test an unknown material , be it Alum. Mag or whatever with a very basic idea , instead of spending an hour grinding and fitting and then find out my project wasn't compatible for weld , I would clean a small spot and build up a small post , perhaps 1/4 in. dia. and 1/4 in. high , clamp onto the post with a vise grip and put some torque load on the post or pillar and see how it broke , if it takes a lot of twist and finally pulls some of the base metal as it breaks , I would be satisfied to go ahead and weld , if the pillar falls off or snaps very easy , you can stop and try something else . Good Luck , Phil L.
Or,using a clean file or sharp knife, file or scrape a bit off the suspected material and try to light it. Magnesium burns :-)
Bruce-in-Bangkok (correct email address for reply)
If you have room to be a little destructive, you can drill it and/or scrape it a bit with a sharp knife.
What little mag I have worked with seems to be a bit more silver in color, and have dusty or flakey cuttings or chips.
Aluminum will appear more white in color by comparison, and the chips or shavings will appear more soft or gummy.
Mag always seems to "appear" harder than aluminum, sometimes even causing a drill bit to squeal as it cuts.
If you get a "known" piece of both materials together and experiment with drilling, filing and scraping them - I think you get a feel for it.
If you can afford enough damage to grind test, they grind very differently as well.
Get it really hot and drop it into a bucket of water. If it burns your shop down it was magnesium.