Bill,
Last time I was in the auto parts store there were 5 different colors of premixed antifreeze. There is inorganic acid technology (IAT), organic acid technology (OAT), and hybrid organic acid technology (HOAT) antifreeze currently available. It can be very confusing and is relative to protecting the metal and sealing combinations of modern engines and cooling systems. But antifreeze can do damage under certain conditions, especially in model engines. Case in point, I have a model engine that sits on a 6061 Al mounting block mated to another 6061 AL plate. Years ago some green 50/50 premix antifreeze leaked out of the engine and seeped between the two AL pieces. I knew some got in there but didn't think it would matter. 4 years later I needed to separate those two plates. What I found was a lot of white gritty powder and two very deeply pitted aluminum surfaces. From that experience I have deduced that if you repeatedly drain an aluminum model engine antifreeze cooling system after each use and let the cooling system dry out then you could see something similar to my experience. I don't begin to chemically understand permanent glycol based antifreeze solutions and what happens to them as their water content is reduced to little or nothing as they dry out. But hey, they are comprised of inorganic and organic acids and AL is a highly reactive metal. Be cautious.
Jeff