Identifying Keel Layers - Need for Primer?

[chholden58]

Hi all,

First time boat owner (and now repairer) looking for some clarification on using a primer underneath anti-fouling paint. And identifying the many layers we are dealing with.
I have attached some photos of the lead keel which have been sanded down (to bare lead in some spots) to repair a Catalina smile & other cracking.
We have applied G-flex over the cracks, sanded with 60/80 grit, and are ready for the next steps.
Is a primer (like Interlux 2000E) necessary? If so, would it be advisable to sand off all remaining anti fouling paint (red) before applying?

The boat does stay on a slip all season, it is not trailered. I will be adding an update to note which antifouling paint I will be using.

Thank you!

 

[ggrizzard]

The good news is that, with a lead keel, you don't have to worry about rust removal
and special mitigation.
The bad news is if you don't strip it down to bare lead now, the sea critters will find the weak spots
in the barrier coat/anti foul that is left and make a home there, creating more work to remove them later.

 

[shemandr]

I think you don't need a barrier coat on the lead keel because barrier coats are made to protect the fiberglass laminate from water intrusion. Water doesn't seep into lead through osmosis or any other process. So no barrier coat.
The keel needs protection from marine growth with antifouling coating. Many of which depend on Copper to inhibit marine critters from colonizing on the keel. It seems like good practice to me to separate the lead from the copper with a coating of epoxy over the lead and before the antifouling.
It's best practice to remove all previous coatings so that you know what is covering what. But practically doing such might not be worth time/effort/expense.

 

[Blitz]

go to the interlux website, it clearly indicates a barrier coat primer or regular primer over the lead prior to applying bottom paint.

 

[Davidasailor26]

go to the interlux website, it clearly indicates a barrier coat primer or regular primer over the lead prior to applying bottom paint.

See page 12 at https://www.international-yachtpain...911.85414827.1685615242-1512048660.1685615242 about priming underwater metals. The “barrier coat” product is very good for this, but doesn’t really act as a barrier coat (which takes many layers) just a single primer coat. Acting as a primer it helps make sure the antifouling adheres well to the metal, and that if the antifouling wears or chips the metal is still covered so overcoating with more anti fouling is much easier.

 

[Crazy Dave Condon]

Most dealer and yards applied epoxy barrier coats on lead keels.
Cast iron keels need a primer paint to keep the iron from oxidizing or rusting first