Automotive water pump corrosion is often caused by metal particles in the fluid.
Most castings are cheaply made, and of sub-standard alloys.
Also you should note, automotive pumps fail 80% of the time, do to bearings, not seals.
The strain the belts place on the pump bearing is VERY large, even more so in the last 10 years, where one belt is used on the whole motor.
Recently manufactures have been using wider belts, which reduce total stress, hence pump last much longer then to past.
If I see that pic right, is that AL against Copper?
Big no-no if so, you need a gasket between then, not just an o-ring.
O-rings should only be used on like or neutral material.
Gaskets are cheaper anyhow, we just cut ours with laser cutter, any shape we want, CAD straight to production cheap and quick.
Take a look at some modern type automotive rads, AL fins / core, plastic caps..... little corrosion
BTW Great forum !
People with real GOOD points, not "troll talk", glad Lee pointed me to it