Mando, I read into (googled) this recently. Stray current, poorly earthed accessories, mixed coolant types - all contribute to corrosion of aluminium radiators. One particular forum post provided excellent information and is well worth a read.
http://www.qldstreetscene.com/forums...ium-radiators/
I'm aware this doesn't answer your question but thought I'd share the info anyway. It certainly helped me.
Cheers
Paul