Yep, you're right. I was thinking of titanium. :) If anyone's interested in details of Aluminium anodising, this seems like a decently thorough introduction:

Yep, you're right. I was thinking of titanium. :) If anyone's interested in details of Aluminium anodising, this seems like a decently thorough introduction: https://nzic.org.nz/unsecure_files/book/8E.pdf https://nzic.org.nz/unsecure_files/book/8E.pdf