From everything I've heard/experienced/found you don't really need to take any actions in terms of preventing your engine from corroding with something like this. It's not a problem at all. You're still running your car mostly on gasoline, so it's a nice oily liquid continually coating the inside of your engine. It will help prevent this, so it's not a problem. It's when you start running purley on Hydroxy that you need to watch out for that, big time. Heat and water = VERY fast rust, as you would notice with a normal exhaust system (always rust out first)
Anyway, also you might hear about a lot of people running water injection in their cars as well. Hydroxy can't be any worse than this, and again it's such a low ratio compared to the fuel that it's not a big deal.
BTW, I had seen that product WAY back...the challenge is an option...