Well take it from me that the silicates are there probably part of the additive package. Silicates are the reason why it does one no good to change a car from the green antifreeze to Dexcool, which is the orange stuff by Texaco and GM. Once the inside of the cooling system is coated with silicates then regular changes of antifreeze are required and the long life virtues of Dexcool are lost because you have to change it anyway just like the green stuff.
Changing antifreeze in cars is to replace the anti-oxidative additive package not the glycol base material which is essentially unaffected by age I believe. So the fact that your antifreeze wears out with use seems to indicate that it is one of the components of the additive package that is doing the cleaning.