Good information guys. As I have mentioned on another thread I am repairing 2 doors with bare metal adhesion issues (bubbles)after 5 years. They were epoxied with PPG DPLF on bare steel after using RustMort. The metal is very shiney and appears to have needed to be sanded better with 80 grit and/or the acid neutralized better. It is odd that they held up well for 3 or 4 years and started to fail badly in the last year.
The tests you guys have done and the follow up information is very much appreciated.