If aluminum is the material used in space then could we not protect it at the outside with a thin layer of steal. It would give an extra protection against debris and small meteorites.

Thanks.

I may have a different proposal....
While i was browsing the net, i stumbled upon some very interesting articles regarding liquid metal. Some of them have incredible strength. If i´m not mistaken, liquid metal (or at least a different combination of it) could be used as armor. IIRC, the US Army is currently tinkering with it.