Aluminium can be left raw and doesnt need alot ot maintenance,
I"ve seen a big increase in the amount of commercial fishing boats and pleasure boats being constructed of aluminum here in the PNW. I used to think it was an ideal material as well because of low maintenance. I'm not so sure anymore. It doesn't take long for aluminum to become pitted from the salt water environment. Should a crack or something develop, it becomes very difficult to repair by welding once this pitting has begun.
I still think it's a strong and fairly durable material, but if I were in the market for an aluminum boat, I would explore their repairability with someone who welds the material.