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  #11  
Old 11-14-2012
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Re: Keel Fix help

DrB, one doesn't apply a barrier coat over a lead keel, since there is nothing to "barrier". The lead doesn't give a damn what kind of water it is immersed in.

OTOH one certainly would apply a fairing coat over a lead keel, to provide a smooth surface. And antifouling paint over that. But then you'd be looking for a FAIRING product, not anything sold as a barrier coat.

Lead forms a thin skin of lead oxide upon exposure to air, and that thin layer of lead oxide is what comes apart and lets the coatings peel off. The trick to good adhesion is a somewhat messy process, you want to clean the lead, and then as you apply the next layer of epoxy fairing compound, scrub it in with a wire brush or metal mesh pads, so that you are scraping away at the oxide coating and allowing the bare lead to bond with what you are applying.

That may take four hands, i.e. yours to apply the goo and scrub it in, and someone else following you to smooth it off. But if you get that first coat scrubbed in so it has bonded with bare lead instead of an oxide coating, it should stick very nicely. Especially if it is an epoxy.

How much fairing you decide to do on the lead, rather than on the filling/fairing layers over it, is something else again.
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Old 11-14-2012
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Re: Keel Fix help

Hello's method sounds pretty effective but I'd change one thing - the first "scrubbing layer" would be a lot easier if it was epoxy resin instead of filler. It would give the same, or better bond for subsequent layers.

Alternatively, going over the keel with a wire cup brush in a small grinder would clean off the oxide layer - lead stays "bright" for quite a while, unlike iron & aluminium so you'd have time to roll on a coat of resin to seal it before a problematic oxide layer formed.
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Old 11-14-2012
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Thanks everyone

Based on the responses, my original approach appears sound. Rough up the exposed lead well (bright surface), coat it with unfilled epoxy, let it set some (tacky),and coat it with filled epoxy, full cure and the feather contour blend into remaining keel.

And yes, I do know that lead oxidizes as does aluminum and most metals. Little tidbit I learned in PhD Materials Eng school. And as you pointed out, bonding to some of these fast forming metal oxides can be an issue.

Thanks all for the advice.

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