If air is present in a Dex system, corrosion begins because Dex doesnt "plate" the surfaces with silicates as green does, but rather needs to be in constant contact with all surfaces to provide its anti corrosive benefits.
Green uses the plating method, which works quite well regardless of air. The only drawback, as the anti corrosion additive package has a shorter life span than does the OAT Dex type coolants....and consequently needs to be replaced about every 3 years.
I dont think that Dex by itself, plays any part in the upper failures we have seen, but that corrosion and the sludge it becomes, if left untreated, may cause many other terrible problems.
If you must stick with Dex or any OAT coolant, flush it every 2-3 yrs, and for pete'* sake, replace the OEM radiator cap with a aftermarket one such as Stant. Also, make sure that your coolant recovery bottle never, never, ever, is empty which will allow air into the system. Maintain that coolant level as though it was your life'* calling.
However, if you observes reddish corrosion on the inside of your existing cap.....flush teh system completely and thoroughly..
If I was to have stuck with a "long life" coolant....... I would have chosen Zerex which provides excellent protection without some of the other brands'* known "issues".
an interesting read on OAT type coolants and issues owners are faced with.