[Leither]

Since no one seems to have covered it so far, I thought a bit of chemistry might be interesting at this point (though if you feel a tendency for your eyes to glaze over at the very mention, then please move on!).

Aluminium is actually a relatively reactive metal. It is higher than zinc or iron in the reactivity series of metals, for example, and only slightly below magnesium. In contact with any metal below it in the series, it will corrode "preferentially" (and, in the process, actually protect the other metal from corrosion ie act as an anode) hence the concerns mentioned about stray currents and contact with other metals.

Aluminium's built in trick is that the oxide which forms on its surface, when in contact with air or water, is waterproof and protects the metal below. This is in contrast to iron, where the oxide (rust) allows water through and the whole damn thing evtually crumbles away (as we all know to our cost!).

If the aluminium oxide layer is damaged, then a new layer forms and maintains protection (assuming no other metals in contact etc).

One of the problems about this oxide layer is that it is relatively soft and easily damaged, so where the metal is exposed to regular abrasion then there could be an erosion problem. This can be overcome to an extent by "hard anodising" which process essentially thickens up the oxide layer and makes it more resistant to abrasion (commonly done in domestic appliances and industrial applications).

As people have mentioned, the quality of the aluminium being used is important. Lower quality metal contains more impurities which set up localised electrolytic "cells" which can cause pinholes and eventual failure.

If you feel over-stimulated as a result of reading this, then I recommend deep breathing and relaxation!

Stuart