there is nothing corosive about alcohol !!!!! we printers use it for damping systems on bare back rubber rollers it also circulates through plastic pipes and comes in contact with brass, copper, nikel, steel, practicly all metals with no corossion efects!
the print industry has spent millions develping its alcohol based damping systems through chiller and no chiller units. it offers reduced water tention so it flows easy, it also gets into every nook and crany, and about a 25% addition will also add cooling effects from any rad!
Ive run alcohol in my water setup for ages with no corrosion and improved flow through less surface tention, use a hydrometer and see for your self people, great stuff for water cooling systems!