... i would like to know how long since you sanded the black off because i think the aluminum get black by corrosion.

No, aluminium goes from a shiney silver to a silver grey due to oxidation in air. The thin oxide layer then protects the aluminuim from further corrosion, as long as you don't go putting it near acid or salty water anyway. It looks OK completely uncoated, but it looks even better anodised or laquered. You can even get clear anodising done - won't be really shiney like laquered aluminium, but it still looks reasonable