This weekend, I was down at my Grandma's house and Dad and I had to prop open her screen door to get in some drywall, when I looked down and saw a piece of the door had flaked off and was lying in the threshold...
I said, "Wow, look at that... Grandma's door has intergranular corrosion!" which made my Dad chuckle.
We had gotten some in-depth schooling from Gary on this type of corrosion when we were down at Midland painting Ol' 927.