Are you sure these breakages are the result of oxidising and not of the alu-magnesium alloy age hardening and becoming brittle and then cracking ?

In the end, anodising is nothing more then thorougly oxidising the outer portion of the aluminium component. The desired result is an extra thick and tight layer of alu-oxide on the surface of the alu element. The Alu-oxide then slows down further oxidising to an almost standstill. This is why plain non-anodised alu can be used just as well; only difference is that it will look less cleam (uniform) as natural oxidising looks more greyish then an anodised oxide layer.

But anodising for 20 bucks is something I wouldn't pass over.

Wouter