Epoxy Primer
I have used both
Sterling 2-component epoxy primers (U-4747 and U-4749) and
Awlgrip's epoxy primer. I do not have any preference, although I have used Sterling more recently.
In the Sterling system, the preferred procedure for surfaces above the waterline is:
Blast to near white metal (almost always impossible for me as part of a refit/repair)
Apply any inorganic zinc primer, allow to dry then quickly apply
20-30 mils of U-4747 primer in 2-3 coats (yellow)
Apply U-4749 high build primer (white)
Sand
Goto step 4 as necessary
Apply U-1000 finish primer (white)
Sand
Goto step 7 as necessary
Topcoat
I can not sandblast, so I replace steps #1 & #2 with a needle scaling, grinding, wire-wheeling, and elbow grease. I plan to try International’s Interzinc 351 as an inorganic zinc primer in a future trial.
I like the combination of yellow and white primers. By changing colors, I have a guide when painting (cover the previous color) and a guide for sanding to prevent burn through (stop sanding when the color changes).