sounds like you got your torch pugged in the [+] positive, if you have, change it to the [-] negative. i think i a right here.

dont know if it matters, but Thoriated tungstens are for steel, not Ali. (as far as i know)

Hi, not got any experience (yet) but that welding rod you need might be

Hastelloy W

Do a search on here, the man who knows said something about it.

HTH

johnny