Anodizing is removed by alkalies, anything with a negative Ph will eventually remove anodizing. Hard anodizing -the kind you find on high end aluminum cookware- stands up sort of well but doesn't really lend itself to the look most people want in a pen. Not sure about what acids will do, but anodizing is done in an acid environment (sulphuric acid, the stuff in car batteries).
So I suppose that the ink being used would be quite important.
I've been giving some thought to a dropper fill FP out of aluminum and/or brass, and have been thinking about boring it slightly oversize from what I want to end up with as a bore, casting it full of PR or PU resin and boring it to the size I want effectively leaving a bonded resin lining in it to keep it from contact with the ink so it won't make any difference what is used. Been thinking about the same with wood as well.
Don't know if it will work but with winter and my slow season at hand it's something I intend to at least experiment with.