CaptTom, it is much safer on aluminum than bleach. In the Practical Sailor test they put aluminum discs in solutions of bleach and Purisan. The bleach solution did a lot more damage than the Puriclean.
Both use chlorine as the active ingredient but there is something in Puriclean that protects the aluminum. I asked the manufacturer of Puriclean why it didn't damage aluminum and I got a long explanation that I couldn't really understand.
He talked to me like I hadn't slept through high school chemistry.