There have been a couple of threads discussing corrosion associated with aluminum alloy water pumps:
Although there was considerable conjecture about the cause and prevention, a clear resolution alludes us.
Speculation ran high that it's some form of electrolytic/ionizing process between aluminum and steel, possibly compounded by minerals in the antifreeze diluting water. I'm posting a few photos of what we found when we removed this water pump after four years. Dilution of 50/50 antifreeze and well water had been used, and the well water has low mineral content. It would seem it would take a LOT of mineral to create this amount of buildup. A local radiator repairman said he occasionally sees this associated with aluminum cooling components in reefer trucks, FWIW.
Discussions took both sides of the aluminum/iron debate, the distilled water debate, and the anode debate, so we'd still like to find out how to manage this problem going ahead. Based on the surprise we had here, a lot of owners may be unaware this could be affecting their cooling system, too.
Corrosion almost blocks the engine mount orifice
Looks like chicken ......!
The radiator end has much less deposit
That was a common problem with that brand of water pump. I believe they now use a different alloy. I use only nice old cast iron types.
What is that stuff???? That is nasty.
That looks like stop leak or perhaps oatmeal mixed with chlorine / aluminum reactive corrosion exfoliation.
Was there any anti freeze in the engine or just plain chlorinated tap water?
Either way, ditch the water pump, it is surely not helping the engine in any way, corrosion or not.
As Jerry said that is common with that style of pump, A friend had a brand new brass work radiator with 50-50 anti- freeze that got plugged up and had to have it rodded out, the pump is now gone and runs fine with out it. I have seen it with straight water also. They even had the anode with the Z head what a mess the whole engine was.