That looks *neat*. Is it at all waterproof? Or does dropping a bit of water on it cause the ink to run? Maybe "alumajet" plus something like Krylon Preserve It spray would be an interesting combo. Speaking most generally though, isn't aluminum a pretty "reactive" metal? Not sure it's a good choice for long-term storage... But agree this would be gorgeous e.g. for gifting bitcoins short-term!
It looks neat, but devil is in the details. You are right that aluminum in itself is extremely reactive - so much that it will immediately react with oxygen to form a layer of aluminum oxide on its surface. Any ordinary piece of aluminum you see around is at least self-passivated this way. Alumajet is claimed to be "anodized aluminum" - which means processed to increase the thickness of the oxide layer. While aluminum oxide - think of it as a ceramic - is relatively inert, it is far from durable. Both acids and basescan weaken it. Thermal expansion is ways different from that of underlying aluminum, leading to cracking from hot/cold cycles, then to related localized corrosion. Finally, to be inkjettable, ideally it needs to be somewhat porous. If porous, it's not good passivating layer. Even the manufacturer recommends laminating signs printed on alumajet.
I like the idea behind the product, and might even try printing some photos (color management nightmare, probably), but would not trust it for btc wallet any more than paper.
actually it has some sort of special covering on one side which is the printable one (has to be single face, but it folds nicely) because the ink doesn't stick well on the other side.