Need help in identifying corrosion on aluminum engine parts

I recently purchased an AAR Cuda. At time of purchase the hoses that attach to all aluminum parts were "ballooned out" at the hose clamps (see heater hose in photo of engine). When I disassembled the engine down to the short block and removed the hoses, there was extreme corrosion under all of the hoses connected to aluminum parts. The corrosion was white and crumbled easily when dried, almost like table salt. I completely flushed the block, hot tanked the intake, replaced the water pump and thermostat housing, etc. and didn't think much more about it. I just thought the prior owner never changed the coolant. After the engine was reassembled I ran it on an engine stand with clean tap water for coolant. When finished I drained the block and set the engine aside while I completed the restoration on the rest of the car. As it turns I had to remove the thermostat housing today and when I did, it appears the corrosion is back (see thermostat housing pic). What the heck is this stuff, corrosion? What could be causing it. The engine was run for 30 minutes on a stand, drained and what you see here accumulated in 60 days. Has anyone seen this before? What can I do about it? I need help on this one guys. Thank you.

I would tend to think YOUR tap water is the culprit, try running distilled/de-ionized/RO water and a coolant such as Zerex G-05, and a water wetter like Redline

and consider one of those sacrificial annodes you put in the radiator to help with electrolysis.

I have a alum. block and heads.i use distilled water and WaterWeter and have no corrosion.

i forgot to add, checking the voltage present in your cooling system on a regular basis using a digital vom will tell you when it's time to change your coolant and help to prevent corrosion also.

Thank you, sounds like good advice. Where can I get a sacrificial anode and where does it mount in the radiator?

Thanks again for the info...should be helpful.

Might go to a boat marina local to you, and tell 'em your story...

Be Cool sells them that screw into the fitting on the botom of the radiator where the petcock is

www.classicindustries.com

That's calcium dropout from tap water.

Also guessing it's from lack of use. How often did the previous owner drive it. Many people sell because the classic car just sits there and never gets driven.

http://www.summitracing.com/parts/flx-32060 and in case you have an aftermarket radiator that doesn't have a spot to screw it http://www.summitracing.com/parts/flx-32082 http://www.summitracing.com/parts/flx-32084