One example of a completely destroyed Apogee GTX (corrosion had actually clogged the internals of the block up):


...and a less severe case of corrosion which occurred even with corrosion inhibitors in the coolant.


All corrosion inhibitors will do is slow the corrosion reaction, not stop it. Granted, with strong inhibitors and frequent coolant changes, the reaction can be slowed enough to where you, hypothetically, wouldn't see a whole lot happen during the course of a part's life... but why risk it when there are plenty of alternative materials?