a cast iron keel will have pockets of impurities that set up mini electolytic cells and make rusting inevitable. accept that (a) you will always have rust weeps at the end of the season but (b) as long as you treat them it won't be a problem. even if you left the keel unpainted to rust freely it would still outlast the boat!
Yep! Ignore em. As Snowleopard says. Not a problem. Where the GRP meets the keel is the only bit worth worrying about as rust in the "joint" can cause problems. In this area it's worth wire brushing and giving a couple of coats of epoxy tar around the keel to about 4 ins below the joint before antifouling. Otherwise forget it.
I agree with Snowleopard regarding cast iron, but you are sure these keels are not mild steel? It is much less common, but if they might be, better care is advisable. As Boatmike says, I would go with an epoxy tar primer and also a tie coat beneath the antifouling.
yep , got same problem.
nothing to worry about,me thinks.
with 45 % ballast ratio , a couple of ounces ground off evry couple of years to make things smooth (2 1/2 tons displacement) and treated with good quality rust inhibitor which doesn't seem to work very well either.
estimate it will take me about 4000 years to grind a hole in the keels.
In these warm parts antifouling is very important. The rust on the keel quickly lifts off the A/F and the weeds and barnacles gather. So rust is good to treat. however if you don't have a fouling problem then don't worry. will