Zinc primer in submerged service non-potable, blisters?

[viking123]

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 that specifying topcoated zinc underwater is poor practice. Eventually, the topcoat will be compromised and the zinc primer will be exposed to water. When it is exposed to water, it reacts and forms blisters, causing the system to fail."

What would cause the blisters to form I have seen something like this occur with a micaceous iron oxide and zinc polyurethane primer that when compromised blisters were spread throughout, any thoughts or experience on this?

 

[CoryPad]

This link provides a lot of good information on blistering of zinc-rich coatings during immersion service:

http://events.nace.org/seminars/ccc_series/2009_SEPT/presentations/Reals.pdf

 

[viking123]

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/