Alumiinium used for extrusions is usually 6063 or 6061 grade. ^063 is a lot softer, 6061 being twice as hard. Beer cans and the like are made from a much lighter and softer alloy, usually the 1000 series - they are really soft. The finish on Ally can vary according to which grade you use. 6063 is given the name architectural aluminium as it gives a much smoother surface than other grades and has an element of corrosion resistance. Those who tell you that Aluminium doesnt corrode are wrong! Most aluminium provides an oxide coating that provides the protection on exposure to oxygen, the difference between corrosion on steel is that the corrosion - rust - is itself aggresive and it will eat into the material whereas the oxide on aluminium will normally stop the corrosion. However, Aluminium provides that resistance not of its own accord but as a result of the differeing levels of silicon, manganese and others that are mixed during the smelting process.
Woody got a cracking finish on his pen and I suspect but could be wrong that it is 6063 alloy, its a good bet as it does account for about 60% of the aluminium in circulation.
Glue to bond aluminium to wood - CA is not a good idea. The reason for this is that the catalyst for the exothermic reaction that is the curing process for CA is moisture and it does not bond well to metal despite the fact that many continue to use it to bond tubes to blanks. It will adhere but it is a very weak bond. CA works well with porous surfaces, metal is not porous, and vice versa will not give up moisture to initiate the curing process.
