Any question answered...

And there was us mortals thinking aluminium was safe from corrosion

Pure aluminium is actually quite resistant to corrosion. It's also about as strong as cheese. The alloying elements which go into aluminium alloys to make them strong enough to use as handlebars also tend to make them much more susceptible to corrosion, particularly stress corrosion cracking, and particularly when there are chloride ions present (as in sweat and salted roads).

There is a kind of material called Alclad which is used in aerospace structures specifically to address this, using a high strength alloy core clad in high purity aluminium.