Thanks for this useful information.
In this case the primer is Polyurethane (modified aromatic) thus I believe organic and similar blistering occurred in certain areas, likely similar mechanism?
a few pictures
http://s1302.photobucket.com/user/sktmike/library/
thread332-327161
I am starting a new thread as a side bar of:
Zinc Primer for Potable Water Tank - Will Zinc Become the "New Lead"?
In that thread there was mention of when coating is compromised and zinc primer is exposed to liquid it can/will react and form blisters.
"Basically, they say...