Just curious if this is normal wear or if something was added to it to do this? I was thinking someone used tap water, or maybe stop leak.

 

Corrosion like that happens when people don't flush their coolant system every year or 2. In cold climates you're supposed to flush and fill every spring and fall...in warmer areas you can go a year or 2 between flushings.

Most people just let it ride, maybe top it off every couple months. Then they overheat and blow a head gasket because their cooling system is too clogged to be effective.